Author name code: schuehle
ADS astronomy entries on 2022-09-14
=author:"Schuele, U." OR author:"Schuehle, Udo" 
------------------------------------------------------------------------  

Title: What drives decayless kink oscillations in active region
    coronal loops on the Sun?
Authors: Mandal, Sudip; Chitta, Lakshmi P.; Antolin, Patrick; Peter,
   Hardi; Solanki, Sami K.; Auchère, Frédéric; Berghmans, David;
   Zhukov, Andrei N.; Teriaca, Luca; Cuadrado, Regina A.; Schühle,
   Udo; Parenti, Susanna; Buchlin, Éric; Harra, Louise; Verbeeck, Cis;
   Kraaikamp, Emil; Long, David M.; Rodriguez, Luciano; Pelouze, Gabriel;
   Schwanitz, Conrad; Barczynski, Krzysztof; Smith, Phil J.
Bibcode: 2022arXiv220904251M
Altcode:
  We study here the phenomena of decayless kink oscillations in a system
  of active region (AR) coronal loops. Using high resolution observations
  from two different instruments, namely the Extreme Ultraviolet Imager
  (EUI) on board Solar Orbiter and the Atmospheric Imaging Assembly
  (AIA) on board the Solar Dynamics Observatory, we follow these AR
  loops for an hour each on three consecutive days. Our results show
  significantly more resolved decayless waves in the higher-resolution
  EUI data compared with the AIA data. Furthermore, the same system of
  loops exhibits many of these decayless oscillations on Day-2, while on
  Day-3, we detect very few oscillations and on Day-1, we find none at
  all. Analysis of photospheric magnetic field data reveals that at most
  times, these loops were rooted in sunspots, where supergranular flows
  are generally absent. This suggests that supergranular flows, which
  are often invoked as drivers of decayless waves, are not necessarily
  driving such oscillations in our observations. Similarly, our findings
  also cast doubt on other possible drivers of these waves, such as a
  transient driver or mode conversion of longitudinal waves near the loop
  footpoints. In conclusion, through our analysis we find that none of
  the commonly suspected sources proposed to drive decayless oscillations
  in active region loops seems to be operating in this event and hence,
  the search for that elusive wave driver needs to continue.

Title: The Lyman-$\alpha$ Emission in a C1.4 Solar Flare Observed
    by the Extreme Ultraviolet Imager aboard Solar Orbiter
Authors: Li, Ying; Li, Qiao; Song, De-Chao; Battaglia, Andrea
   Francesco; Xiao, Hualin; Krucker, Säm; Schühle, Udo; Li, Hui; Gan,
   Weiqun; Ding, M. D.
Bibcode: 2022arXiv220806182L
Altcode:
  The hydrogen Lyman-$\alpha$ (H {\sc i} Ly$\alpha$) emission during solar
  flares has rarely been studied in spatially resolved images and its
  physical origin has not been fully understood. In this paper, we present
  novel Ly$\alpha$ images for a C1.4 solar flare (SOL2021-08-20T22:00)
  from the Extreme Ultraviolet Imager aboard Solar Orbiter, together
  with multi-waveband and multi-perspective observations from the
  Solar Terrestrial Relations Observatory Ahead and the Solar Dynamics
  Observatory spacecraft. It is found that the Ly$\alpha$ emission has
  a good temporal correlation with the thermal emissions at 1--8 Å and
  5--7 keV, indicating that the flaring Ly$\alpha$ is mainly produced by
  a thermal process in this small event. However, nonthermal electrons
  play a minor role in generating Ly$\alpha$ at flare ribbons during
  the rise phase of the flare, as revealed by the hard X-ray imaging and
  spectral fitting. Besides originating from flare ribbons, the Ly$\alpha$
  emission can come from flare loops, likely caused by plasma heating
  and also cooling that happen in different flare phases. It is also
  found that the Ly$\alpha$ emission shows fairly similar features with
  the He {\sc ii} 304 Å emission in light curve and spatio-temporal
  variation along with small differences. These observational results
  improve our understanding of the Ly$\alpha$ emission in solar flares
  and also provide some insights for investigating the Ly$\alpha$
  emission in stellar flares.

Title: A highly dynamic small-scale jet in a polar coronal hole
Authors: Mandal, Sudip; Chitta, Lakshmi Pradeep; Peter, Hardi;
   Solanki, Sami K.; Cuadrado, Regina Aznar; Teriaca, Luca; Schühle,
   Udo; Berghmans, David; Auchère, Frédéric
Bibcode: 2022A&A...664A..28M
Altcode: 2022arXiv220602236M
  We present an observational study of the plasma dynamics at the base
  of a solar coronal jet, using high resolution extreme ultraviolet
  imaging data taken by the Extreme Ultraviolet Imager on board Solar
  Orbiter, and by the Atmospheric Imaging Assembly on board Solar
  Dynamics Observatory. We observed multiple plasma ejection events
  over a period of ∼1 h from a dome-like base that is ca. 4 Mm wide
  and is embedded in a polar coronal hole. Within the dome below the
  jet spire, multiple plasma blobs with sizes around 1−2 Mm propagate
  upwards to the dome apex with speeds of the order of the sound speed
  (ca. 120 km s<SUP>−1</SUP>). Upon reaching the apex, some of these
  blobs initiate flows with similar speeds towards the other footpoint
  of the dome. At the same time, high speed super-sonic outflows
  (∼230 km s<SUP>−1</SUP>) are detected along the jet spire. These
  outflows as well as the intensity near the dome apex appear to be
  repetitive. Furthermore, during its evolution, the jet undergoes
  many complex morphological changes, including transitions between
  the standard and blowout type eruption. These new observational
  results highlight the underlying complexity of the reconnection
  process that powers these jets and they also provide insights into
  the plasma response when subjected to rapid energy injection. <P
  />Movies associated to Figs. 1, 2, and 4 are available at <A
  href="https://www.aanda.org/10.1051/0004-6361/202243765/olm">https://www.aanda.org</A>

Title: Linking Small-scale Solar Wind Properties with Large-scale
    Coronal Source Regions through Joint Parker Solar Probe-Metis/Solar
    Orbiter Observations
Authors: Telloni, Daniele; Zank, Gary P.; Sorriso-Valvo, Luca;
   D'Amicis, Raffaella; Panasenco, Olga; Susino, Roberto; Bruno, Roberto;
   Perrone, Denise; Adhikari, Laxman; Liang, Haoming; Nakanotani, Masaru;
   Zhao, Lingling; Hadid, Lina Z.; Sánchez-Cano, Beatriz; Verscharen,
   Daniel; Velli, Marco; Grimani, Catia; Marino, Raffaele; Carbone,
   Francesco; Mancuso, Salvatore; Biondo, Ruggero; Pagano, Paolo; Reale,
   Fabio; Bale, Stuart D.; Kasper, Justin C.; Case, Anthony W.; de Wit,
   Thierry Dudok; Goetz, Keith; Harvey, Peter R.; Korreck, Kelly E.;
   Larson, Davin; Livi, Roberto; MacDowall, Robert J.; Malaspina, David
   M.; Pulupa, Marc; Stevens, Michael L.; Whittlesey, Phyllis; Romoli,
   Marco; Andretta, Vincenzo; Deppo, Vania Da; Fineschi, Silvano; Heinzel,
   Petr; Moses, John D.; Naletto, Giampiero; Nicolini, Gianalfredo;
   Spadaro, Daniele; Stangalini, Marco; Teriaca, Luca; Capobianco,
   Gerardo; Capuano, Giuseppe E.; Casini, Chiara; Casti, Marta; Chioetto,
   Paolo; Corso, Alain J.; Leo, Yara De; Fabi, Michele; Frassati,
   Federica; Frassetto, Fabio; Giordano, Silvio; Guglielmino, Salvo L.;
   Jerse, Giovanna; Landini, Federico; Liberatore, Alessandro; Magli,
   Enrico; Massone, Giuseppe; Messerotti, Mauro; Pancrazzi, Maurizio;
   Pelizzo, Maria G.; Romano, Paolo; Sasso, Clementina; Schühle, Udo;
   Slemer, Alessandra; Straus, Thomas; Uslenghi, Michela; Volpicelli,
   Cosimo A.; Zangrilli, Luca; Zuppella, Paola; Abbo, Lucia; Auchère,
   Frédéric; Cuadrado, Regina Aznar; Berlicki, Arkadiusz; Ciaravella,
   Angela; Lamy, Philippe; Lanzafame, Alessandro; Malvezzi, Marco;
   Nicolosi, Piergiorgio; Nisticò, Giuseppe; Peter, Hardi; Solanki,
   Sami K.; Strachan, Leonard; Tsinganos, Kanaris; Ventura, Rita; Vial,
   Jean-Claude; Woch, Joachim; Zimbardo, Gaetano
Bibcode: 2022ApJ...935..112T
Altcode:
  The solar wind measured in situ by Parker Solar Probe in the very
  inner heliosphere is studied in combination with the remote-sensing
  observation of the coronal source region provided by the METIS
  coronagraph aboard Solar Orbiter. The coronal outflows observed near
  the ecliptic by Metis on 2021 January 17 at 16:30 UT, between 3.5 and
  6.3 R <SUB>⊙</SUB> above the eastern solar limb, can be associated
  with the streams sampled by PSP at 0.11 and 0.26 au from the Sun,
  in two time intervals almost 5 days apart. The two plasma flows
  come from two distinct source regions, characterized by different
  magnetic field polarity and intensity at the coronal base. It follows
  that both the global and local properties of the two streams are
  different. Specifically, the solar wind emanating from the stronger
  magnetic field region has a lower bulk flux density, as expected,
  and is in a state of well-developed Alfvénic turbulence, with low
  intermittency. This is interpreted in terms of slab turbulence in the
  context of nearly incompressible magnetohydrodynamics. Conversely,
  the highly intermittent and poorly developed turbulent behavior of the
  solar wind from the weaker magnetic field region is presumably due to
  large magnetic deflections most likely attributed to the presence of
  switchbacks of interchange reconnection origin.

Title: The on-ground data reduction and calibration pipeline for
    SO/PHI-HRT
Authors: Sinjan, J.; Calchetti, D.; Hirzberger, J.; Orozco Suárez,
   D.; Albert, K.; Albelo Jorge, N.; Appourchaux, T.; Alvarez-Herrero,
   A.; Blanco Rodríguez, J.; Gandorfer, A.; Germerott, D.; Guerrero,
   L.; Gutierrez Marquez, P.; Kahil, F.; Kolleck, M.; Solanki, S. K.; del
   Toro Iniesta, J. C.; Volkmer, R.; Woch, J.; Fiethe, B.; Gómez Cama,
   J. M.; Pérez-Grande, I.; Sanchis Kilders, E.; Balaguer Jiménez,
   M.; Bellot Rubio, L. R.; Carmona, M.; Deutsch, W.; Fernandez-Rico,
   G.; Fernández-Medina, A.; García Parejo, P.; Gasent Blesa, J. L.;
   Gizon, L.; Grauf, B.; Heerlein, K.; Korpi-Lagg, A.; Lange, T.; López
   Jiménez, A.; Maue, T.; Meller, R.; Michalik, H.; Moreno Vacas, A.;
   Müller, R.; Nakai, E.; Schmidt, W.; Schou, J.; Schühle, U.; Staub,
   J.; Strecker, H.; Torralbo, I.; Valori, G.
Bibcode: 2022arXiv220814904S
Altcode:
  The ESA/NASA Solar Orbiter space mission has been successfully launched
  in February 2020. Onboard is the Polarimetric and Helioseismic Imager
  (SO/PHI), which has two telescopes, a High Resolution Telescope
  (HRT) and the Full Disc Telescope (FDT). The instrument is designed
  to infer the photospheric magnetic field and line-of-sight velocity
  through differential imaging of the polarised light emitted by the
  Sun. It calculates the full Stokes vector at 6 wavelength positions
  at the Fe I 617.3 nm absorption line. Due to telemetry constraints,
  the instrument nominally processes these Stokes profiles onboard,
  however when telemetry is available, the raw images are downlinked and
  reduced on ground. Here the architecture of the on-ground pipeline
  for HRT is presented, which also offers additional corrections not
  currently available on board the instrument. The pipeline can reduce
  raw images to the full Stokes vector with a polarimetric sensitivity
  of $10^{-3}\cdot I_{c}$ or better.

Title: Coronal Microjets in Quiet-sun Regions Observed with the
    Extreme Ultraviolet Imager Onboard Solar Orbiter
Authors: Hou, Zhenyong; He, Jiansen; Berghmans, David; Teriaca, Luca;
   Wang, Linghua; Schuehle, Udo; Tian, Hui; Chen, Yajie; Chen, Hechao;
   Gao, Yuhang; Bai, Xianyong
Bibcode: 2022cosp...44.2536H
Altcode:
  We report the smallest coronal jets ever observed in the quiet Sun
  with recent high resolution observations from the High Resolution
  Telescopes (HRI-EUV and HRI-Lyα) of the Extreme Ultraviolet
  Imager (EUI) onboard Solar Orbiter. In the HRI-EUV (174 Å) images,
  these microjets usually appear as nearly collimated structures with
  brightenings at their footpoints. Their average lifetime, projected
  speed, width, and maximum length are 4.6 min, 62 km $s^{-1}$, 1.0 Mm,
  and 7.7 Mm, respectively. Inverted-Y shaped structures and moving blobs
  can be identified in some events. A subset of these events also reveal
  signatures in the HRI-Lyα (H I Lyα at 1216 Å) images and the extreme
  ultraviolet images taken by the Atmospheric Imaging Assembly onboard the
  Solar Dynamics Observatory. Our differential emission measure analysis
  suggests a multi-thermal nature and an average density of ~1.4x10^9
  $cm^{-3}$ for these microjets. Their thermal and kinetic energies were
  estimated to be ~3.9x10$^{24}$ erg and ~2.9x10$^{23}$ erg, respectively,
  which are of the same order of the released energy predicted by the
  nanoflare theory. Most events appear to be located at the edges of
  network lanes and magnetic flux concentrations, suggesting that these
  coronal microjets are likely generated by magnetic reconnection between
  small-scale magnetic loops and the adjacent network field.

Title: Automatic detection of small-scale EUV brightenings observed
    by the Solar Orbiter/EUI
Authors: Alipour, N.; Safari, H.; Verbeeck, C.; Berghmans, D.;
   Auchère, F.; Chitta, L. P.; Antolin, P.; Barczynski, K.; Buchlin,
   É.; Aznar Cuadrado, R.; Dolla, L.; Georgoulis, M. K.; Gissot, S.;
   Harra, L.; Katsiyannis, A. C.; Long, D. M.; Mandal, S.; Parenti,
   S.; Podladchikova, O.; Petrova, E.; Soubrié, É.; Schühle, U.;
   Schwanitz, C.; Teriaca, L.; West, M. J.; Zhukov, A. N.
Bibcode: 2022A&A...663A.128A
Altcode: 2022arXiv220404027A
  Context. Accurate detections of frequent small-scale extreme ultraviolet
  (EUV) brightenings are essential to the investigation of the physical
  processes heating the corona. <BR /> Aims: We detected small-scale
  brightenings, termed campfires, using their morphological and
  intensity structures as observed in coronal EUV imaging observations
  for statistical analysis. <BR /> Methods: We applied a method based
  on Zernike moments and a support vector machine (SVM) classifier
  to automatically identify and track campfires observed by Solar
  Orbiter/Extreme Ultraviolet Imager (EUI) and Solar Dynamics Observatory
  (SDO)/Atmospheric Imaging Assembly (AIA). <BR /> Results: This method
  detected 8678 campfires (with length scales between 400 km and 4000 km)
  from a sequence of 50 High Resolution EUV telescope (HRI<SUB>EUV</SUB>)
  174 Å images. From 21 near co-temporal AIA images covering the same
  field of view as EUI, we found 1131 campfires, 58% of which were
  also detected in HRI<SUB>EUV</SUB> images. In contrast, about 16%
  of campfires recognized in HRI<SUB>EUV</SUB> were detected by AIA. We
  obtain a campfire birthrate of 2 × 10<SUP>−16</SUP> m<SUP>−2</SUP>
  s<SUP>−1</SUP>. About 40% of campfires show a duration longer than 5
  s, having been observed in at least two HRI<SUB>EUV</SUB> images. We
  find that 27% of campfires were found in coronal bright points and
  the remaining 73% have occurred out of coronal bright points. We
  detected 23 EUI campfires with a duration greater than 245 s. We found
  that about 80% of campfires are formed at supergranular boundaries,
  and the features with the highest total intensities are generated at
  network junctions and intense H I Lyman-α emission regions observed
  by EUI/HRI<SUB>Lya</SUB>. The probability distribution functions for
  the total intensity, peak intensity, and projected area of campfires
  follow a power law behavior with absolute indices between 2 and 3. This
  self-similar behavior is a possible signature of self-organization,
  or even self-organized criticality, in the campfire formation
  process. <P />Supplementary material (S1-S3) is available at <A
  href="https://www.aanda.org/10.1051/0004-6361/202243257/olm">https://www.aanda.org</A>

Title: The SPICE spectrograph on Solar Orbiter: an introduction and
    results from the first Orbits
Authors: Auchère, Frédéric; Peter, Hardi; Parenti, Susanna; Buchlin,
   Eric; Thompson, William; Auchere, Frederic; Teriaca, Luca; Kucera,
   Therese; Carlsson, Mats; Janvier, Miho; Fludra, Andrzej; Giunta,
   Alessandra; Schuehle, Udo; Hassler, Donald M.; Grundy, Timothy;
   Sidher, Sunil; Fredvik, Terje; Plowman, Joseph; Aznar Cuadrado, Regina
Bibcode: 2022cosp...44.1338A
Altcode:
  The Spectral Imaging of the Coronal Environment (SPICE) instrument is
  the EUV imaging spectrometer on board the Solar Orbiter mission. With
  its ability to derive physical properties of the coronal plasma,
  SPICE is a key component of the payload to establish the connection
  between the source regions and the in-situ measurements of the solar
  wind. The spacecraft was successfully launched in February 2020 and
  completed its cruise phase in December 2021. During this period,
  the remote sensing instruments were mostly operated during limited
  periods of time for 'checkout' engineering activities and synoptic
  observations. Nonetheless, several of these periods provided enough
  opportunities already to obtain new insights on coronal physics. During
  the march 2022 perihelion - close to 0.3 AU - SPICE will provide
  its highest spatial resolution data so far. Coordinated observations
  between the remote sensing and in-situ instruments will provide the
  first opportunity to use the full potential of the Solar Orbiter
  mission. We will review the instrument characteristics and present
  initial results from the cruise phase and first close encounter.

Title: Observation of Magnetic Switchback in the Solar Corona
Authors: Telloni, Daniele; Zank, Gary P.; Stangalini, Marco;
   Downs, Cooper; Liang, Haoming; Nakanotani, Masaru; Andretta,
   Vincenzo; Antonucci, Ester; Sorriso-Valvo, Luca; Adhikari, Laxman;
   Zhao, Lingling; Marino, Raffaele; Susino, Roberto; Grimani, Catia;
   Fabi, Michele; D'Amicis, Raffaella; Perrone, Denise; Bruno, Roberto;
   Carbone, Francesco; Mancuso, Salvatore; Romoli, Marco; Da Deppo, Vania;
   Fineschi, Silvano; Heinzel, Petr; Moses, John D.; Naletto, Giampiero;
   Nicolini, Gianalfredo; Spadaro, Daniele; Teriaca, Luca; Frassati,
   Federica; Jerse, Giovanna; Landini, Federico; Pancrazzi, Maurizio;
   Russano, Giuliana; Sasso, Clementina; Berghmans, David; Auchère,
   Frédéric; Aznar Cuadrado, Regina; Chitta, Lakshmi P.; Harra, Louise;
   Kraaikamp, Emil; Long, David M.; Mandal, Sudip; Parenti, Susanna;
   Pelouze, Gabriel; Peter, Hardi; Rodriguez, Luciano; Schühle, Udo;
   Schwanitz, Conrad; Smith, Phil J.; Verbeeck, Cis; Zhukov, Andrei N.
Bibcode: 2022arXiv220603090T
Altcode:
  Switchbacks are sudden, large radial deflections of the solar wind
  magnetic field, widely revealed in interplanetary space by the Parker
  Solar Probe. The switchbacks' formation mechanism and sources are still
  unresolved, although candidate mechanisms include Alfvénic turbulence,
  shear-driven Kelvin-Helmholtz instabilities, interchange reconnection,
  and geometrical effects related to the Parker spiral. This Letter
  presents observations from the Metis coronagraph onboard Solar Orbiter
  of a single large propagating S-shaped vortex, interpreted as first
  evidence of a switchback in the solar corona. It originated above
  an active region with the related loop system bounded by open-field
  regions to the East and West. Observations, modeling, and theory provide
  strong arguments in favor of the interchange reconnection origin of
  switchbacks. Metis measurements suggest that the initiation of the
  switchback may also be an indicator of the origin of slow solar wind.

Title: The magnetic drivers of campfires seen by the Polarimetric
    and Helioseismic Imager (PHI) on Solar Orbiter
Authors: Kahil, F.; Hirzberger, J.; Solanki, S. K.; Chitta, L. P.;
   Peter, H.; Auchère, F.; Sinjan, J.; Orozco Suárez, D.; Albert,
   K.; Albelo Jorge, N.; Appourchaux, T.; Alvarez-Herrero, A.; Blanco
   Rodríguez, J.; Gandorfer, A.; Germerott, D.; Guerrero, L.; Gutiérrez
   Márquez, P.; Kolleck, M.; del Toro Iniesta, J. C.; Volkmer, R.;
   Woch, J.; Fiethe, B.; Gómez Cama, J. M.; Pérez-Grande, I.; Sanchis
   Kilders, E.; Balaguer Jiménez, M.; Bellot Rubio, L. R.; Calchetti,
   D.; Carmona, M.; Deutsch, W.; Fernández-Rico, G.; Fernández-Medina,
   A.; García Parejo, P.; Gasent-Blesa, J. L.; Gizon, L.; Grauf, B.;
   Heerlein, K.; Lagg, A.; Lange, T.; López Jiménez, A.; Maue, T.;
   Meller, R.; Michalik, H.; Moreno Vacas, A.; Müller, R.; Nakai,
   E.; Schmidt, W.; Schou, J.; Schühle, U.; Staub, J.; Strecker, H.;
   Torralbo, I.; Valori, G.; Aznar Cuadrado, R.; Teriaca, L.; Berghmans,
   D.; Verbeeck, C.; Kraaikamp, E.; Gissot, S.
Bibcode: 2022A&A...660A.143K
Altcode: 2022arXiv220213859K
  Context. The Extreme Ultraviolet Imager (EUI) on board the Solar Orbiter
  (SO) spacecraft observed small extreme ultraviolet (EUV) bursts,
  termed campfires, that have been proposed to be brightenings near the
  apexes of low-lying loops in the quiet-Sun atmosphere. The underlying
  magnetic processes driving these campfires are not understood. <BR
  /> Aims: During the cruise phase of SO and at a distance of 0.523
  AU from the Sun, the Polarimetric and Helioseismic Imager on Solar
  Orbiter (SO/PHI) observed a quiet-Sun region jointly with SO/EUI,
  offering the possibility to investigate the surface magnetic field
  dynamics underlying campfires at a spatial resolution of about 380
  km. <BR /> Methods: We used co-spatial and co-temporal data of the
  quiet-Sun network at disc centre acquired with the High Resolution
  Imager of SO/EUI at 17.4 nm (HRI<SUB>EUV</SUB>, cadence 2 s) and the
  High Resolution Telescope of SO/PHI at 617.3 nm (HRT, cadence 2.5
  min). Campfires that are within the SO/PHI−SO/EUI common field
  of view were isolated and categorised according to the underlying
  magnetic activity. <BR /> Results: In 71% of the 38 isolated events,
  campfires are confined between bipolar magnetic features, which seem to
  exhibit signatures of magnetic flux cancellation. The flux cancellation
  occurs either between the two main footpoints, or between one of the
  footpoints of the loop housing the campfire and a nearby opposite
  polarity patch. In one particularly clear-cut case, we detected the
  emergence of a small-scale magnetic loop in the internetwork followed
  soon afterwards by a campfire brightening adjacent to the location
  of the linear polarisation signal in the photosphere, that is to
  say near where the apex of the emerging loop lays. The rest of the
  events were observed over small scattered magnetic features, which
  could not be identified as magnetic footpoints of the campfire hosting
  loops. <BR /> Conclusions: The majority of campfires could be driven
  by magnetic reconnection triggered at the footpoints, similar to the
  physical processes occurring in the burst-like EUV events discussed
  in the literature. About a quarter of all analysed campfires, however,
  are not associated to such magnetic activity in the photosphere, which
  implies that other heating mechanisms are energising these small-scale
  EUV brightenings.

Title: Stereoscopy of extreme UV quiet Sun brightenings observed by
    Solar Orbiter/EUI
Authors: Zhukov, A. N.; Mierla, M.; Auchère, F.; Gissot, S.;
   Rodriguez, L.; Soubrié, E.; Thompson, W. T.; Inhester, B.; Nicula, B.;
   Antolin, P.; Parenti, S.; Buchlin, É.; Barczynski, K.; Verbeeck, C.;
   Kraaikamp, E.; Smith, P. J.; Stegen, K.; Dolla, L.; Harra, L.; Long,
   D. M.; Schühle, U.; Podladchikova, O.; Aznar Cuadrado, R.; Teriaca,
   L.; Haberreiter, M.; Katsiyannis, A. C.; Rochus, P.; Halain, J. -P.;
   Jacques, L.; Berghmans, D.
Bibcode: 2021A&A...656A..35Z
Altcode: 2021arXiv210902169Z
  Context. The three-dimensional fine structure of the solar atmosphere
  is still not fully understood as most of the available observations
  are taken from a single vantage point. <BR /> Aims: The goal of the
  paper is to study the three-dimensional distribution of the small-scale
  brightening events ("campfires") discovered in the extreme-UV quiet Sun
  by the Extreme Ultraviolet Imager (EUI) aboard Solar Orbiter. <BR />
  Methods: We used a first commissioning data set acquired by the EUI's
  High Resolution EUV telescope on 30 May 2020 in the 174 Å passband and
  we combined it with simultaneous data taken by the Atmospheric Imaging
  Assembly (AIA) aboard the Solar Dynamics Observatory in a similar 171
  Å passband. The two-pixel spatial resolution of the two telescopes
  is 400 km and 880 km, respectively, which is sufficient to identify
  the campfires in both data sets. The two spacecraft had an angular
  separation of around 31.5° (essentially in heliographic longitude),
  which allowed for the three-dimensional reconstruction of the campfire
  position. These observations represent the first time that stereoscopy
  was achieved for brightenings at such a small scale. Manual and
  automatic triangulation methods were used to characterize the campfire
  data. <BR /> Results: The height of the campfires is located between
  1000 km and 5000 km above the photosphere and we find a good agreement
  between the manual and automatic methods. The internal structure of
  campfires is mostly unresolved by AIA; however, for a particularly
  large campfire, we were able to triangulate a few pixels, which are
  all in a narrow range between 2500 and 4500 km. <BR /> Conclusions: We
  conclude that the low height of EUI campfires suggests that they belong
  to the previously unresolved fine structure of the transition region and
  low corona of the quiet Sun. They are probably apexes of small-scale
  dynamic loops heated internally to coronal temperatures. This work
  demonstrates that high-resolution stereoscopy of structures in the
  solar atmosphere has become feasible.

Title: Stereoscopy of extreme UV quiet Sun brightenings observed by
    Solar Orbiter/EUI
Authors: Zhukov, Andrei; Mierla, Marilena; Auchere, F.; Gissot,
   Samuel; Rodriguez, Luciano; Soubrie, Elie; Thompson, William; Inhester,
   Bernd; Nicula, Bogdan; Antolin, Patrick; Parenti, Susanna; Buchlin,
   Eric; Barczynski, Krzysztof; Verbeeck, Cis; Kraaikamp, Emil; Smith,
   Philip; Stegen, Koen; Dolla, Laurent; Harra, Louise; Long, David;
   Schuhle, Udo; Podladchikova, Olena; Aznar Cuadrado, Regina; Teriaca,
   Luca; Haberreiter, Margit; Katsiyannis, Athanassios; Rochus, Pierre;
   Halain, Jean-Philippe; Jacques, Lionel; Berghmans, David
Bibcode: 2021AGUFMSH21A..03Z
Altcode:
  We study the three-dimensional distribution of small-scale brightening
  events (campfires) discovered in the extreme-ultraviolet (EUV) quiet Sun
  by the EUI telescope onboard the Solar Orbiter mission. We use one of
  the first commissioning data sets acquired by the HRI_EUV telescope of
  EUI on 2020 May 30 in the 174 A passband, combined with the simultaneous
  SDO/AIA dataset taken in the very similar 171 A passband. The spatial
  resolution of the two telescopes is sufficient to identify the campfires
  in both datasets. The angular separation between the two spacecraft of
  around 31.5 degrees allowed for the three-dimensional reconstruction
  of the position of campfires. This is the first time that stereoscopy
  was achieved for structures at such a small scale. Manual and automatic
  triangulation methods were used. The height of campfires is between 1000
  km and 5000 km above the photosphere, and there is a good agreement
  between the results of manual and automatic methods. The internal
  structure of campfires is mostly not resolved by AIA, but for a large
  campfire we could triangulate a few pixels, which are all in a narrow
  height range between 2500 and 4500 km. The low height of campfires
  suggests that they belong to the previously unresolved fine structure
  of the transition region and low corona of the quiet Sun. They are
  probably apexes of small-scale dynamic loops internally heated to
  coronal temperatures. This work demonstrates that high-resolution
  stereoscopy of structures in the solar atmosphere has become possible.

Title: Propagating brightenings in small loop-like structures in
the quiet-Sun corona: Observations from Solar Orbiter/EUI
Authors: Mandal, Sudip; Peter, Hardi; Chitta, Lakshmi Pradeep;
   Solanki, Sami K.; Aznar Cuadrado, Regina; Teriaca, Luca; Schühle,
   Udo; Berghmans, David; Auchère, Frédéric
Bibcode: 2021A&A...656L..16M
Altcode: 2021arXiv211108106M
  Brightenings observed in solar extreme-ultraviolet images are generally
  interpreted as signatures of micro- or nanoflares occurring in the
  transition region or at coronal temperatures. Recent observations
  with the Extreme Ultraviolet Imager (EUI) on board Solar Orbiter have
  revealed the smallest of such brightenings (called campfires) in the
  quiet-Sun corona. Analyzing EUI 174 Å data obtained at a resolution
  of about 400 km on the Sun with a cadence of 5 s on 30 May 2020,
  we report here a number of cases in which these campfires exhibit
  propagating signatures along their apparently small (3-5 Mm) loop-like
  structures. The measured propagation speeds are generally between 25
  km s<SUP>−1</SUP> and 60 km s<SUP>−1</SUP>. If the loop plasma is
  assumed to be at a million Kelvin, these apparent motions would be
  slower than the local sound speed. Furthermore, these brightenings
  exhibit nontrivial propagation characteristics such as bifurcation,
  merging, reflection, and repeated plasma ejections. We suggest that
  these features are manifestations of the internal dynamics of these
  small-scale magnetic structures and could provide important insights
  into the dynamic response (∼40 s) of the loop plasma to the heating
  events and also into the locations of the heating events themselves. <P
  />Movies associated to Figs 2-5, A.1, and B.1 are available at <A
  href="https://www.aanda.org/10.1051/0004-6361/202142041/olm">https://www.aanda.org</A>

Title: The first coronal mass ejection observed in both visible-light
    and UV H I Ly-α channels of the Metis coronagraph on board Solar
    Orbiter
Authors: Andretta, V.; Bemporad, A.; De Leo, Y.; Jerse, G.; Landini,
   F.; Mierla, M.; Naletto, G.; Romoli, M.; Sasso, C.; Slemer, A.;
   Spadaro, D.; Susino, R.; Talpeanu, D. -C.; Telloni, D.; Teriaca, L.;
   Uslenghi, M.; Antonucci, E.; Auchère, F.; Berghmans, D.; Berlicki,
   A.; Capobianco, G.; Capuano, G. E.; Casini, C.; Casti, M.; Chioetto,
   P.; Da Deppo, V.; Fabi, M.; Fineschi, S.; Frassati, F.; Frassetto,
   F.; Giordano, S.; Grimani, C.; Heinzel, P.; Liberatore, A.; Magli, E.;
   Massone, G.; Messerotti, M.; Moses, D.; Nicolini, G.; Pancrazzi, M.;
   Pelizzo, M. -G.; Romano, P.; Schühle, U.; Stangalini, M.; Straus,
   Th.; Volpicelli, C. A.; Zangrilli, L.; Zuppella, P.; Abbo, L.; Aznar
   Cuadrado, R.; Bruno, R.; Ciaravella, A.; D'Amicis, R.; Lamy, P.;
   Lanzafame, A.; Malvezzi, A. M.; Nicolosi, P.; Nisticò, G.; Peter,
   H.; Plainaki, C.; Poletto, L.; Reale, F.; Solanki, S. K.; Strachan,
   L.; Tondello, G.; Tsinganos, K.; Velli, M.; Ventura, R.; Vial, J. -C.;
   Woch, J.; Zimbardo, G.
Bibcode: 2021A&A...656L..14A
Altcode:
  Context. The Metis coronagraph on board Solar Orbiter offers a new
  view of coronal mass ejections (CMEs), observing them for the first
  time with simultaneous images acquired with a broad-band filter in
  the visible-light interval and with a narrow-band filter around the
  H I Ly-α line at 121.567 nm, the so-called Metis UV channel. <BR />
  Aims: We show the first Metis observations of a CME, obtained on 16
  and 17 January 2021. The event was also observed by the EUI/FSI imager
  on board Solar Orbiter, as well as by other space-based coronagraphs,
  such as STEREO-A/COR2 and SOHO/LASCO/C2, whose images are combined here
  with Metis data. <BR /> Methods: Different images are analysed here
  to reconstruct the 3D orientation of the expanding CME flux rope using
  the graduated cylindrical shell model. This also allows us to identify
  the possible location of the source region. Measurements of the CME
  kinematics allow us to quantify the expected Doppler dimming in the
  Ly-α channel. <BR /> Results: Observations show that most CME features
  seen in the visible-light images are also seen in the Ly-α images,
  although some features in the latter channel appear more structured
  than their visible-light counterparts. We estimated the expansion
  velocity of this event to be below 140 km s<SUP>−1</SUP>. Hence,
  these observations can be understood by assuming that Doppler dimming
  effects do not strongly reduce the Ly-α emission from the CME. These
  velocities are comparable with or smaller than the radial velocities
  inferred from the same data in a similar coronal structure on the
  east side of the Sun. <BR /> Conclusions: The first observations by
  Metis of a CME demonstrate the capability of the instrument to provide
  valuable and novel information on the structure and dynamics of these
  coronal events. Considering also its diagnostics capabilities regarding
  the conditions of the ambient corona, Metis promises to significantly
  advance our knowledge of such phenomena. <P />Movies are available at <A
  href="https://www.aanda.org/10.1051/0004-6361/202142407/olm">https://www.aanda.org</A>

Title: Extreme-UV quiet Sun brightenings observed by the Solar
    Orbiter/EUI
Authors: Berghmans, D.; Auchère, F.; Long, D. M.; Soubrié, E.;
   Mierla, M.; Zhukov, A. N.; Schühle, U.; Antolin, P.; Harra, L.;
   Parenti, S.; Podladchikova, O.; Aznar Cuadrado, R.; Buchlin, É.;
   Dolla, L.; Verbeeck, C.; Gissot, S.; Teriaca, L.; Haberreiter, M.;
   Katsiyannis, A. C.; Rodriguez, L.; Kraaikamp, E.; Smith, P. J.;
   Stegen, K.; Rochus, P.; Halain, J. P.; Jacques, L.; Thompson, W. T.;
   Inhester, B.
Bibcode: 2021A&A...656L...4B
Altcode: 2021arXiv210403382B
  Context. The heating of the solar corona by small heating events
  requires an increasing number of such events at progressively smaller
  scales, with the bulk of the heating occurring at scales that are
  currently unresolved. <BR /> Aims: The goal of this work is to study the
  smallest brightening events observed in the extreme-UV quiet Sun. <BR />
  Methods: We used commissioning data taken by the Extreme Ultraviolet
  Imager (EUI) on board the recently launched Solar Orbiter mission. On
  30 May 2020, the EUI was situated at 0.556 AU from the Sun. Its
  High Resolution EUV telescope (HRI<SUB>EUV</SUB>, 17.4 nm passband)
  reached an exceptionally high two-pixel spatial resolution of 400
  km. The size and duration of small-scale structures was determined
  by the HRI<SUB>EUV</SUB> data, while their height was estimated
  from triangulation with simultaneous images from the Atmospheric
  Imaging Assembly (AIA) on board the Solar Dynamics Observatory
  mission. This is the first stereoscopy of small-scale brightenings
  at high resolution. <BR /> Results: We observed small localised
  brightenings, also known as `campfires', in a quiet Sun region with
  length scales between 400 km and 4000 km and durations between 10 s and
  200 s. The smallest and weakest of these HRI<SUB>EUV</SUB> brightenings
  have not been previously observed. Simultaneous observations from the
  EUI High-resolution Lyman-α telescope (HRI<SUB>Lya</SUB>) do not show
  localised brightening events, but the locations of the HRI<SUB>EUV</SUB>
  events clearly correspond to the chromospheric network. Comparisons with
  simultaneous AIA images shows that most events can also be identified
  in the 17.1 nm, 19.3 nm, 21.1 nm, and 30.4 nm pass-bands of AIA,
  although they appear weaker and blurred. Our differential emission
  measure analysis indicated coronal temperatures peaking at log T ≈
  6.1 − 6.15. We determined the height for a few of these campfires to
  be between 1000 and 5000 km above the photosphere. <BR /> Conclusions:
  We find that `campfires' are mostly coronal in nature and rooted in the
  magnetic flux concentrations of the chromospheric network. We interpret
  these events as a new extension to the flare-microflare-nanoflare
  family. Given their low height, the EUI `campfires' could stand as a
  new element of the fine structure of the transition region-low corona,
  that is, as apexes of small-scale loops that undergo internal heating
  all the way up to coronal temperatures.

Title: Capturing transient plasma flows and jets in the solar corona
Authors: Chitta, L. P.; Solanki, S. K.; Peter, H.; Aznar Cuadrado,
   R.; Teriaca, L.; Schühle, U.; Auchère, F.; Berghmans, D.; Kraaikamp,
   E.; Gissot, S.; Verbeeck, C.
Bibcode: 2021A&A...656L..13C
Altcode: 2021arXiv210915106C
  Intensity bursts in ultraviolet (UV) to X-ray wavelengths and plasma
  jets are typical signatures of magnetic reconnection and the associated
  impulsive heating of the solar atmospheric plasma. To gain new insights
  into the process, high-cadence observations are required to capture
  the rapid response of plasma to magnetic reconnection as well as the
  highly dynamic evolution of jets. Here, we report the first 2 s cadence
  extreme-UV observations recorded by the 174 Å High Resolution Imager of
  the Extreme Ultraviolet Imager on board the Solar Orbiter mission. These
  observations, covering a quiet-Sun coronal region, reveal the onset
  signatures of magnetic reconnection as localized heating events. These
  localized sources then exhibit repeated plasma eruptions or jet
  activity. Our observations show that this spatial morphological change
  from localized sources to jet activity could occur rapidly on timescales
  of about 20 s. The jets themselves are intermittent and are produced
  from the source region on timescales of about 20 s. In the initial
  phases of these events, plasma jets are observed to exhibit speeds,
  as inferred from propagating intensity disturbances, in the range of
  100 km s<SUP>−1</SUP> to 150 km s<SUP>−1</SUP>. These jets then
  propagate to lengths of about 5 Mm. We discuss examples of bidirectional
  and unidirectional jet activity observed to have been initiated from
  the initially localized bursts in the corona. The transient nature
  of coronal bursts and the associated plasma flows or jets along with
  their dynamics could provide a benchmark for magnetic reconnection
  models of coronal bursts and jets. <P />Movies are available at <A
  href="https://www.aanda.org/10.1051/0004-6361/202141683/olm">https://www.aanda.org</A>

Title: Cosmic-ray flux predictions and observations for and with
    Metis on board Solar Orbiter
Authors: Grimani, C.; Andretta, V.; Chioetto, P.; Da Deppo, V.; Fabi,
   M.; Gissot, S.; Naletto, G.; Persici, A.; Plainaki, C.; Romoli, M.;
   Sabbatini, F.; Spadaro, D.; Stangalini, M.; Telloni, D.; Uslenghi, M.;
   Antonucci, E.; Bemporad, A.; Capobianco, G.; Capuano, G.; Casti, M.;
   De Leo, Y.; Fineschi, S.; Frassati, F.; Frassetto, F.; Heinzel, P.;
   Jerse, G.; Landini, F.; Liberatore, A.; Magli, E.; Messerotti, M.;
   Moses, D.; Nicolini, G.; Pancrazzi, M.; Pelizzo, M. G.; Romano, P.;
   Sasso, C.; Schühle, U.; Slemer, A.; Straus, T.; Susino, R.; Teriaca,
   L.; Volpicelli, C. A.; Freiherr von Forstner, J. L.; Zuppella, P.
Bibcode: 2021A&A...656A..15G
Altcode: 2021arXiv210413700G
  Context. The Metis coronagraph is one of the remote sensing instruments
  hosted on board the ESA/NASA Solar Orbiter mission. Metis is devoted
  to carry out the first simultaneous imaging of the solar corona in
  both visible light (VL) and ultraviolet (UV). High-energy particles
  can penetrate spacecraft materials and may limit the performance of
  the on-board instruments. A study of the galactic cosmic-ray (GCR)
  tracks observed in the first VL images gathered by Metis during the
  commissioning phase is presented here. A similar analysis is planned
  for the UV channel. <BR /> Aims: We aim to formulate a prediction of
  the GCR flux up to hundreds of GeV for the first part of the Solar
  Orbiter mission to study the performance of the Metis coronagraph. <BR
  /> Methods: The GCR model predictions are compared to observations
  gathered on board Solar Orbiter by the High-Energy Telescope in the
  range between 10 MeV and 100 MeV in the summer of 2020 as well as with
  the previous measurements. Estimated cosmic-ray fluxes above 70 MeV
  n<SUP>−1</SUP> have been also parameterized and used for Monte Carlo
  simulations aimed at reproducing the cosmic-ray track observations in
  the Metis coronagraph VL images. The same parameterizations can also
  be used to study the performance of other detectors. <BR /> Results:
  By comparing observations of cosmic-ray tracks in the Metis VL images
  with FLUKA Monte Carlo simulations of cosmic-ray interactions in
  the VL detector, we find that cosmic rays fire only a fraction, on
  the order of 10<SUP>−4</SUP>, of the whole image pixel sample. We
  also find that the overall efficiency for cosmic-ray identification
  in the Metis VL images is approximately equal to the contribution
  of Z ≥ 2 GCR particles. A similar study will be carried out during
  the whole of the Solar Orbiter's mission duration for the purposes of
  instrument diagnostics and to verify whether the Metis data and Monte
  Carlo simulations would allow for a long-term monitoring of the GCR
  proton flux.

Title: First observations from the SPICE EUV spectrometer on Solar
    Orbiter
Authors: Fludra, A.; Caldwell, M.; Giunta, A.; Grundy, T.; Guest,
   S.; Leeks, S.; Sidher, S.; Auchère, F.; Carlsson, M.; Hassler, D.;
   Peter, H.; Aznar Cuadrado, R.; Buchlin, É.; Caminade, S.; DeForest,
   C.; Fredvik, T.; Haberreiter, M.; Harra, L.; Janvier, M.; Kucera, T.;
   Müller, D.; Parenti, S.; Schmutz, W.; Schühle, U.; Solanki, S. K.;
   Teriaca, L.; Thompson, W. T.; Tustain, S.; Williams, D.; Young, P. R.;
   Chitta, L. P.
Bibcode: 2021A&A...656A..38F
Altcode: 2021arXiv211011252F
  <BR /> Aims: We present first science observations taken during the
  commissioning activities of the Spectral Imaging of the Coronal
  Environment (SPICE) instrument on the ESA/NASA Solar Orbiter
  mission. SPICE is a high-resolution imaging spectrometer operating at
  extreme ultraviolet (EUV) wavelengths. In this paper we illustrate
  the possible types of observations to give prospective users a
  better understanding of the science capabilities of SPICE. <BR />
  Methods: We have reviewed the data obtained by SPICE between April
  and June 2020 and selected representative results obtained with
  different slits and a range of exposure times between 5 s and 180
  s. Standard instrumental corrections have been applied to the raw
  data. <BR /> Results: The paper discusses the first observations
  of the Sun on different targets and presents an example of the full
  spectra from the quiet Sun, identifying over 40 spectral lines from
  neutral hydrogen and ions of carbon, oxygen, nitrogen, neon, sulphur,
  magnesium, and iron. These lines cover the temperature range between
  20 000 K and 1 million K (10 MK in flares), providing slices of the
  Sun's atmosphere in narrow temperature intervals. We provide a list
  of count rates for the 23 brightest spectral lines. We show examples
  of raster images of the quiet Sun in several strong transition region
  lines, where we have found unusually bright, compact structures in the
  quiet Sun network, with extreme intensities up to 25 times greater
  than the average intensity across the image. The lifetimes of these
  structures can exceed 2.5 hours. We identify them as a transition
  region signature of coronal bright points and compare their areas and
  intensity enhancements. We also show the first above-limb measurements
  with SPICE above the polar limb in C III, O VI, and Ne VIII lines, and
  far off limb measurements in the equatorial plane in Mg IX, Ne VIII,
  and O VI lines. We discuss the potential to use abundance diagnostics
  methods to study the variability of the elemental composition that can
  be compared with in situ measurements to help confirm the magnetic
  connection between the spacecraft location and the Sun's surface,
  and locate the sources of the solar wind. <BR /> Conclusions: The
  SPICE instrument successfully performs measurements of EUV spectra
  and raster images that will make vital contributions to the scientific
  success of the Solar Orbiter mission.

Title: First light observations of the solar wind in the outer corona
    with the Metis coronagraph
Authors: Romoli, M.; Antonucci, E.; Andretta, V.; Capuano, G. E.; Da
   Deppo, V.; De Leo, Y.; Downs, C.; Fineschi, S.; Heinzel, P.; Landini,
   F.; Liberatore, A.; Naletto, G.; Nicolini, G.; Pancrazzi, M.; Sasso,
   C.; Spadaro, D.; Susino, R.; Telloni, D.; Teriaca, L.; Uslenghi,
   M.; Wang, Y. -M.; Bemporad, A.; Capobianco, G.; Casti, M.; Fabi, M.;
   Frassati, F.; Frassetto, F.; Giordano, S.; Grimani, C.; Jerse, G.;
   Magli, E.; Massone, G.; Messerotti, M.; Moses, D.; Pelizzo, M. -G.;
   Romano, P.; Schühle, U.; Slemer, A.; Stangalini, M.; Straus, T.;
   Volpicelli, C. A.; Zangrilli, L.; Zuppella, P.; Abbo, L.; Auchère,
   F.; Aznar Cuadrado, R.; Berlicki, A.; Bruno, R.; Ciaravella, A.;
   D'Amicis, R.; Lamy, P.; Lanzafame, A.; Malvezzi, A. M.; Nicolosi,
   P.; Nisticò, G.; Peter, H.; Plainaki, C.; Poletto, L.; Reale, F.;
   Solanki, S. K.; Strachan, L.; Tondello, G.; Tsinganos, K.; Velli,
   M.; Ventura, R.; Vial, J. -C.; Woch, J.; Zimbardo, G.
Bibcode: 2021A&A...656A..32R
Altcode: 2021arXiv210613344R
  In this work, we present an investigation of the wind in the solar
  corona that has been initiated by observations of the resonantly
  scattered ultraviolet emission of the coronal plasma obtained with
  UVCS-SOHO, designed to measure the wind outflow speed by applying
  Doppler dimming diagnostics. Metis on Solar Orbiter complements the
  UVCS spectroscopic observations that were performed during solar
  activity cycle 23 by simultaneously imaging the polarized visible
  light and the H I Lyman-α corona in order to obtain high spatial and
  temporal resolution maps of the outward velocity of the continuously
  expanding solar atmosphere. The Metis observations, taken on May 15,
  2020, provide the first H I Lyman-α images of the extended corona
  and the first instantaneous map of the speed of the coronal plasma
  outflows during the minimum of solar activity and allow us to identify
  the layer where the slow wind flow is observed. The polarized visible
  light (580-640 nm) and the ultraviolet H I Lyα (121.6 nm) coronal
  emissions, obtained with the two Metis channels, were combined in
  order to measure the dimming of the UV emission relative to a static
  corona. This effect is caused by the outward motion of the coronal
  plasma along the direction of incidence of the chromospheric photons
  on the coronal neutral hydrogen. The plasma outflow velocity was then
  derived as a function of the measured Doppler dimming. The static
  corona UV emission was simulated on the basis of the plasma electron
  density inferred from the polarized visible light. This study leads
  to the identification, in the velocity maps of the solar corona, of
  the high-density layer about ±10° wide, centered on the extension
  of a quiet equatorial streamer present at the east limb - the coronal
  origin of the heliospheric current sheet - where the slowest wind
  flows at about 160 ± 18 km s<SUP>−1</SUP> from 4 R<SUB>⊙</SUB>
  to 6 R<SUB>⊙</SUB>. Beyond the boundaries of the high-density layer,
  the wind velocity rapidly increases, marking the transition between
  slow and fast wind in the corona.

Title: Exploring the Solar Wind from Its Source on the Corona into
    the Inner Heliosphere during the First Solar Orbiter-Parker Solar
    Probe Quadrature
Authors: Telloni, Daniele; Andretta, Vincenzo; Antonucci, Ester;
   Bemporad, Alessandro; Capuano, Giuseppe E.; Fineschi, Silvano;
   Giordano, Silvio; Habbal, Shadia; Perrone, Denise; Pinto, Rui F.;
   Sorriso-Valvo, Luca; Spadaro, Daniele; Susino, Roberto; Woodham, Lloyd
   D.; Zank, Gary P.; Romoli, Marco; Bale, Stuart D.; Kasper, Justin C.;
   Auchère, Frédéric; Bruno, Roberto; Capobianco, Gerardo; Case,
   Anthony W.; Casini, Chiara; Casti, Marta; Chioetto, Paolo; Corso,
   Alain J.; Da Deppo, Vania; De Leo, Yara; Dudok de Wit, Thierry;
   Frassati, Federica; Frassetto, Fabio; Goetz, Keith; Guglielmino,
   Salvo L.; Harvey, Peter R.; Heinzel, Petr; Jerse, Giovanna; Korreck,
   Kelly E.; Landini, Federico; Larson, Davin; Liberatore, Alessandro;
   Livi, Roberto; MacDowall, Robert J.; Magli, Enrico; Malaspina, David
   M.; Massone, Giuseppe; Messerotti, Mauro; Moses, John D.; Naletto,
   Giampiero; Nicolini, Gianalfredo; Nisticò, Giuseppe; Panasenco,
   Olga; Pancrazzi, Maurizio; Pelizzo, Maria G.; Pulupa, Marc; Reale,
   Fabio; Romano, Paolo; Sasso, Clementina; Schühle, Udo; Stangalini,
   Marco; Stevens, Michael L.; Strachan, Leonard; Straus, Thomas; Teriaca,
   Luca; Uslenghi, Michela; Velli, Marco; Verscharen, Daniel; Volpicelli,
   Cosimo A.; Whittlesey, Phyllis; Zangrilli, Luca; Zimbardo, Gaetano;
   Zuppella, Paola
Bibcode: 2021ApJ...920L..14T
Altcode: 2021arXiv211011031T
  This Letter addresses the first Solar Orbiter (SO)-Parker Solar
  Probe (PSP) quadrature, occurring on 2021 January 18 to investigate
  the evolution of solar wind from the extended corona to the inner
  heliosphere. Assuming ballistic propagation, the same plasma volume
  observed remotely in the corona at altitudes between 3.5 and 6.3
  solar radii above the solar limb with the Metis coronagraph on SO
  can be tracked to PSP, orbiting at 0.1 au, thus allowing the local
  properties of the solar wind to be linked to the coronal source region
  from where it originated. Thanks to the close approach of PSP to the
  Sun and the simultaneous Metis observation of the solar corona, the
  flow-aligned magnetic field and the bulk kinetic energy flux density
  can be empirically inferred along the coronal current sheet with an
  unprecedented accuracy, allowing in particular estimation of the Alfvén
  radius at 8.7 solar radii during the time of this event. This is thus
  the very first study of the same solar wind plasma as it expands from
  the sub-Alfvénic solar corona to just above the Alfvén surface.

Title: Coronal Microjets in Quiet-Sun Regions Observed with the
    Extreme Ultraviolet Imager on Board the Solar Orbiter
Authors: Hou, Zhenyong; Tian, Hui; Berghmans, David; Chen, Hechao;
   Teriaca, Luca; Schühle, Udo; Gao, Yuhang; Chen, Yajie; He, Jiansen;
   Wang, Linghua; Bai, Xianyong
Bibcode: 2021ApJ...918L..20H
Altcode: 2021arXiv210808718H
  We report the smallest coronal jets ever observed in the quiet Sun with
  recent high-resolution observations from the High Resolution Telescopes
  (HRI<SUB>EUV</SUB> and HRI<SUB>Lyα</SUB>) of the Extreme Ultraviolet
  Imager on board the Solar Orbiter (SO). In the HRI<SUB>EUV</SUB>
  (174 Å) images, these microjets usually appear as nearly collimated
  structures with brightenings at their footpoints. Their average
  lifetime, projected speed, width, and maximum length are 4.6 minutes,
  62 km s<SUP>-1</SUP>, 1.0 Mm, and 7.7 Mm, respectively. Inverted-Y
  shaped structures and moving blobs can be identified in some events. A
  subset of these events also reveal signatures in the HRI<SUB>Lyα</SUB>
  (H I Lyα at 1216 Å) images and the extreme ultraviolet images
  taken by the Atmospheric Imaging Assembly (AIA) on board the Solar
  Dynamics Observatory (SDO). Our differential emission-measure (EM)
  analysis suggests a multithermal nature and an average density of ~1.4
  × 10<SUP>9</SUP> cm<SUP>-3</SUP> for these microjets. Their thermal
  and kinetic energies were estimated to be ~3.9 × 10<SUP>24</SUP> erg
  and ~2.9 × 10<SUP>23</SUP> erg, respectively, which are of the same
  order of the released energy predicted by the nanoflare theory. Most
  events appear to be located at the edges of network lanes and magnetic
  flux concentrations, suggesting that these coronal microjets are likely
  generated by magnetic reconnection between small-scale magnetic loops
  and the adjacent network field.

Title: Challenges during Metis-Solar Orbiter commissioning phase
Authors: Romoli, Marco; Andretta, Vincenzo; Bemporad, Alessandro;
   Casti, Marta; Da Deppo, Vania; De Leo, Yara; Fabi, Michele; Fineschi,
   Silvano; Frassetto, Fabio; Grimani, Catia; Heerlein, Klaus; Heinzel,
   Petr; Jerse, Giovanna; Landini, Federico; Liberatore, Alessandro;
   Magli, Enrico; Naletto, Giampiero; Nicolini, Gianalfredo; Pancrazzi,
   Maurizio; Pelizzo, Maria Guglielmina; Romano, Paolo; Sasso, Clementina;
   Schühle, Udo; Slemer, Alessandra; Spadaro, Daniele; Straus, Thomas;
   Susino, Roberto; Teriaca, Luca; Uslenghi, Michela; Volpicelli, Cosimo
   Antonio; Zupella, Paola
Bibcode: 2021SPIE11852E..5AR
Altcode:
  Metis is the visible light and UV light imaging coronagraph on board
  the ESA-NASA mission Solar Orbiter that has been launched February 10th,
  2020, from Cape Canaveral. Scope of the mission is to study the Sun up
  close, taking high-resolution images of the Sun's poles for the first
  time, and understanding the Sun-Earth connection. Metis coronagraph
  will image the solar corona in the linearly polarized broadband visible
  radiation and in the UV HI Ly-α line from 1.6 to 3 solar radii when at
  Solar Orbiter perihelion, providing a diagnostics, with unprecedented
  temporal coverage and spatial resolution, of the structures and dynamics
  of the full corona. Solar Orbiter commissioning phase big challenge was
  Covid-19 social distancing phase that affected the way commissioning
  of a spacecraft and its payload is typically done. Metis coronagraph
  on-board Solar Orbiter had its additional challenges: to wake up and
  check the performance of the optical, electrical and thermal subsystems,
  most of them unchecked since Metis delivery to spacecraft prime, Airbus,
  in May 2017. The roadmap to the fully commissioned coronagraph is here
  described throughout the steps from the software functional test,
  the switch on of the detectors of the two channels, UV and visible,
  to the optimization of the occulting system and the characterization
  of the instrumental stray light, one of the most challenging features
  in a coronagraph.

Title: Calibrating Optical Distortions In The Solar Orbiter Spice
    Spectrograph
Authors: Thompson, W.; Schühle, U.; Young, P.
Bibcode: 2021AAS...23831302T
Altcode:
  The Spectral Imaging of the Coronal Environment (SPICE) instrument on
  SolarOrbiter is a high-resolution imaging spectrometer operating at
  extremeultraviolet (EUV) wavelengths from 70.4-79.0 nm and 97.3-104.9
  nm. Asingle-mirror off-axis paraboloid focuses the solar image onto the
  entranceslit of the spectrometer section. A Toroidal Variable Line Space
  (TVLS)grating images the entrance slit onto a pair of MCP-intensified
  APS detectors.Ray-tracing analysis prior to launch showed that the
  instrument was subject toa number of small image distortions which
  need to be corrected in the finaldata product. We compare the ray
  tracing results with measurements made inflight. Co-alignment with
  other telescopes on Solar Orbiter will also beexamined.

Title: The Extreme ultraviolet imager onboard Solar Orbiter
Authors: Berghmans, David; Harra, Louise K.; Zhukov, Andrei; Auchere,
   Frederic; Long, David; Schuehle, Udo; Rochus, Pierre
Bibcode: 2021cosp...43E.949B
Altcode:
  The Extreme Ultraviolet Imager (EUI) is part of the remote sensing
  instrument package of the ESA/NASA Solar Orbiter mission that will
  explore the inner heliosphere and observe the Sun from vantage points
  close to the Sun and out of the ecliptic. With EUI we aim to improve our
  understanding of the structure and dynamics of the solar atmosphere,
  globally as well as at high resolution, and from high solar latitude
  perspectives. The EUI consists of three telescopes, the Full Sun Imager
  (FSI) and two High Resolution Imagers (HRIs), which are optimised
  to image in Lyman-$\alpha$ and EUV (174 \AA, 304 \AA) to provide a
  coverage from chromosphere up to corona. The EUI instrument design
  will be reviewed, and its scientific objectives and plans will be
  discussed. Early results of the EUI commissioning will be presented.

Title: Relative coronal abundance diagnostics with Solar Orbiter/SPICE
Authors: Zambrana Prado, N.; Buchlin, E.; Peter, H.; Young, P. R.;
   Auchere, F.; Carlsson, M.; Fludra, A.; Hassler, D.; Aznar Cuadrado,
   R.; Caminade, S.; Caldwell, M.; DeForest, C.; Fredvik, T.; Harra,
   L.; Janvier, M.; Kucera, T. A.; Giunta, A. S.; Grundy, T.; Müller,
   D.; Parenti, S.; Schmutz, W. K.; Schühle, U.; Sidher, S.; Teriaca,
   L.; Thompson, W. T.; Williams, D.
Bibcode: 2020AGUFMSH038..09Z
Altcode:
  Linking solar activity on the surface and in the corona to the inner
  heliosphere is one of Solar Orbiter's main goals. Its UV spectrometer
  SPICE (SPectral Imaging of the Coronal Environment) will provide
  relative abundance measurements which will be key in this quest
  as different structures on the Sun have different abundances as a
  consequence of the FIP (First Ionization Potential) effect. Solar
  Orbiter's unique combination of remote sensing and in-situ instruments
  coupled with observation from other missions such as Parker Solar
  Probe will allow us to compare in-situ and remote sensing composition
  data. With the addition of modeling, these new results will allow us
  to trace back the source of heliospheric plasma. As high telemetry
  will not always be available with SPICE, we have developed a method
  for measuring relative abundances that is both telemetry efficient
  and reliable. Unlike methods based on Differential Emission Measure
  (DEM) inversion, the Linear Combination Ratio (LCR) method does not
  require a large number of spectral lines. This new method is based
  on linear combinations of UV spectral lines. The coefficients of
  the combinations are optimized such that the ratio of two linear
  combinations of radiances would yield the relative abundance of two
  elements. We present some abundance diagnostics tested on different
  combinations of spectral lines observable by SPICE.

Title: Dynamics and thermal structure in the quiet Sun seen by SPICE
Authors: Peter, H.; Aznar Cuadrado, R.; Schühle, U.; Teriaca, L.;
   Auchere, F.; Carlsson, M.; Fludra, A.; Hassler, D.; Buchlin, E.;
   Caminade, S.; Caldwell, M.; DeForest, C.; Fredvik, T.; Harra, L. K.;
   Janvier, M.; Kucera, T. A.; Giunta, A. S.; Grundy, T.; Müller, D.;
   Parenti, S.; Schmutz, W. K.; Sidher, S.; Thompson, W. T.; Williams,
   D.; Young, P. R.
Bibcode: 2020AGUFMSH038..03P
Altcode:
  We will present some of the early data of the Spectral Imaging of the
  Coronal Environment (SPICE) instrument on Solar Orbiter. One of the
  unique features of SPICE is its capability to record a wide range of
  wavelengths in the extreme UV with the possibility to record spectral
  lines giving access to a continuous plasma temperature range from 10.000
  K to well above 1 MK. The data taken so far were for commissioning
  purposes and they can be used for a preliminary evaluation of the
  science performance of the instrument. Here we will concentrate on
  sample spectra covering the whole wavelength region and on the early
  raster maps acquired in bright lines in the quiet Sun close to disk
  center. Looking at different quiet Sun features we investigate the
  thermal structure of the atmosphere and flow structures. For this
  we apply fits to the spectral profiles and check the performance in
  terms of Doppler shifts and line widths to retrieve the structure of
  the network in terms of dynamics. While the amount of data available
  so far is limited, we will have a first look on how quiet Sun plasma
  responds to heating events. For this, we will compare spectral lines
  forming at different temperatures recorded at strictly the same time.

Title: Observation of Smallest Ever Detected Brightening Events with
    the Solar Orbiter EUI HRI-EUV Imager
Authors: Parenti, S.; Berghmans, D.; Buchlin, E.; Teriaca, L.; Auchere,
   F.; Harra, L.; Long, D.; Rochus, P. L.; Schühle, U.; Aznar Cuadrado,
   R.; Gissot, S.; Kraaikamp, E.; Smith, P.; Stegen, K.; Verbeeck, C.
Bibcode: 2020AGUFMSH038..01P
Altcode:
  The Extreme Ultraviolet Imager (EUI) suite on board Solar Orbiter
  acquired its first images in May 2020. The passband of the 17.4 nm
  High Resolution Imager (HRI-EUV) is dominated by emission lines of
  Fe IX and Fe X, that is the 1 million degree solar corona. The solar
  atmosphere at this temperature is dynamic at all scales, down to the
  highest spatial resolution available from instruments priori to Solar
  Orbiter. During the Commissioning phase, HRI-EUV acquired several high
  temporal resolution (a few seconds) sequences at quiet Sun regions at
  disk center. The instrument revealed a multitude of brightenings at
  the smallest-ever detectable spatial scales which, at that time, was
  about 400 km (two pixels). These events appear to be present everywhere
  all the time. We present the first results of the analysis of these
  sequences with the aim of understanding the role of these small scale
  events in the heating of the solar corona.

Title: First Results From SPICE EUV Spectrometer on Solar Orbiter
Authors: Fludra, A.; Caldwell, M.; Giunta, A. S.; Grundy, T.; Guest,
   S.; Sidher, S.; Auchere, F.; Carlsson, M.; Hassler, D.; Peter, H.;
   Aznar Cuadrado, R.; Buchlin, E.; Caminade, S.; DeForest, C.; Fredvik,
   T.; Harra, L. K.; Janvier, M.; Kucera, T. A.; Leeks, S.; Mueller,
   D.; Parenti, S.; Schmutz, W. K.; Schühle, U.; Teriaca, L.; Thompson,
   W. T.; Tustain, S.; Williams, D.; Young, P. R.
Bibcode: 2020AGUFMSH038..02F
Altcode:
  SPICE (Spectral Imaging of Coronal Environment) is one of the remote
  sensing instruments onboard Solar Orbiter. It is an EUV imaging
  spectrometer observing the Sun in two wavelength bands: 69.6-79.4 nm
  and 96.6-105.1 nm. SPICE is capable of recording full spectra in these
  bands with exposures as short as 1s. SPICE is the only Solar Orbiter
  instrument that can measure EUV spectra from the disk and low corona
  of the Sun and record all spectral lines simultaneously. SPICE uses
  one of three narrow slits, 2"x11', 4''x11', 6''x11', or a wide slit
  30''x14'. The primary mirror can be scanned in a direction perpendicular
  to the slit, allowing raster images of up to 16' in size. <P />We
  present an overview of the first SPICE data taken on several days
  during the instrument commissioning carried out by the RAL Space team
  between 2020 April 21 and 2020 June 14. We also include results from
  SPICE observations at the first Solar Orbiter perihelion at 0.52AU,
  taken between June 16-21<SUP>st</SUP>. We give examples of full spectra
  from the quiet Sun near disk centre and provide a list of key spectral
  lines emitted in a range of temperatures between 10,000 K and over 1
  million K, from neutral hydrogen and ions of carbon, oxygen, nitrogen,
  neon, sulphur and magnesium. We show examples of first raster images
  in several strong lines, obtained with different slits and a range
  of exposure times between 5s and 180s. We describe the temperature
  coverage and density diagnostics, determination of plasma flows, and
  discuss possible applications to studies of the elemental abundances
  in the corona. We also show the first off-limb measurements with SPICE,
  as obtained when the spacecraft pointed at the limb.

Title: The Solar-C (EUVST) mission: the latest status
Authors: Shimizu, Toshifumi; Imada, Shinsuke; Kawate, Tomoko; Suematsu,
   Yoshinori; Hara, Hirohisa; Tsuzuki, Toshihiro; Katsukawa, Yukio; Kubo,
   Masahito; Ishikawa, Ryoko; Watanabe, Tetsuya; Toriumi, Shin; Ichimoto,
   Kiyoshi; Nagata, Shin'ichi; Hasegawa, Takahiro; Yokoyama, Takaaki;
   Watanabe, Kyoko; Tsuno, Katsuhiko; Korendyke, Clarence M.; Warren,
   Harry; De Pontieu, Bart; Boerner, Paul; Solanki, Sami K.; Teriaca,
   Luca; Schuehle, Udo; Matthews, Sarah; Long, David; Thomas, William;
   Hancock, Barry; Reid, Hamish; Fludra, Andrzej; Auchère, Frederic;
   Andretta, Vincenzo; Naletto, Giampiero; Poletto, Luca; Harra, Louise
Bibcode: 2020SPIE11444E..0NS
Altcode:
  Solar-C (EUVST) is the next Japanese solar physics mission to
  be developed with significant contributions from US and European
  countries. The mission carries an EUV imaging spectrometer with
  slit-jaw imaging system called EUVST (EUV High-Throughput Spectroscopic
  Telescope) as the mission payload, to take a fundamental step towards
  answering how the plasma universe is created and evolves and how the
  Sun influences the Earth and other planets in our solar system. In
  April 2020, ISAS (Institute of Space and Astronautical Science) of JAXA
  (Japan Aerospace Exploration Agency) has made the final down-selection
  for this mission as the 4th in the series of competitively chosen
  M-class mission to be launched with an Epsilon launch vehicle in mid
  2020s. NASA (National Aeronautics and Space Administration) has selected
  this mission concept for Phase A concept study in September 2019 and
  is in the process leading to final selection. For European countries,
  the team has (or is in the process of confirming) confirmed endorsement
  for hardware contributions to the EUVST from the national agencies. A
  recent update to the mission instrumentation is to add a UV spectral
  irradiance monitor capability for EUVST calibration and scientific
  purpose. This presentation provides the latest status of the mission
  with an overall description of the mission concept emphasizing on key
  roles of the mission in heliophysics research from mid 2020s.

Title: Calibrating optical distortions in the Solar Orbiter SPICE
    spectrograph
Authors: Thompson, W. T.; Schühle, U.; Young, P. R.; Auchere, F.;
   Carlsson, M.; Fludra, A.; Hassler, D.; Peter, H.; Aznar Cuadrado, R.;
   Buchlin, E.; Caldwell, M.; DeForest, C.; Fredvik, T.; Harra, L. K.;
   Janvier, M.; Kucera, T. A.; Giunta, A. S.; Grundy, T.; Müller, D.;
   Parenti, S.; Caminade, S.; Schmutz, W. K.; Teriaca, L.; Williams,
   D.; Sidher, S.
Bibcode: 2020AGUFMSH0360029T
Altcode:
  The Spectral Imaging of the Coronal Environment (SPICE) instrument on
  Solar Orbiter is a high-resolution imaging spectrometer operating
  at extreme ultraviolet (EUV) wavelengths from 70.4-79.0 nm and
  97.3-104.9 nm. A single-mirror off-axis paraboloid focuses the solar
  image onto the entrance slit of the spectrometer section. A Toroidal
  Variable Line Space (TVLS) grating images the entrance slit onto a
  pair of MCP-intensified APS detectors. Ray-tracing analysis prior
  to launch showed that the instrument was subject to a number of
  small image distortions which need to be corrected in the final data
  product. We compare the ray tracing results with measurements made in
  flight. Co-alignment with other telescopes on Solar Orbiter will also
  be examined.

Title: First results from the EUI and SPICE observations of Alpha
    Leo near Solar Orbiter first perihelion
Authors: Buchlin, E.; Teriaca, L.; Giunta, A. S.; Grundy, T.; Andretta,
   V.; Auchere, F.; Peter, H.; Berghmans, D.; Carlsson, M.; Fludra, A.;
   Harra, L.; Hassler, D.; Long, D.; Rochus, P. L.; Schühle, U.; Aznar
   Cuadrado, R.; Caldwell, M.; Caminade, S.; DeForest, C.; Fredvik, T.;
   Gissot, S.; Heerlein, K.; Janvier, M.; Kraaikamp, E.; Kucera, T. A.;
   Müller, D.; Parenti, S.; Schmutz, W. K.; Sidher, S.; Smith, P.;
   Stegen, K.; Thompson, W. T.; Verbeeck, C.; Williams, D.; Young, P. R.
Bibcode: 2020AGUFMSH0360024B
Altcode:
  On June 16th 2020 Solar Orbiter made a dedicated observing campaign
  where the spacecraft pointed to the solar limb to allow some of the
  high resolution instruments to observe the ingress (at the east limb)
  and later the egress (west limb) of the occultation of the star Alpha
  Leonis by the solar disk. The star was chosen because its luminosity and
  early spectral type ensure high and stable flux at wavelengths between
  100 and 122 nanometers, a range observed by the High Resolution EUI
  Lyman alpha telescope (HRI-LYA) and by the long wavelength channel
  of the SPICE spectrograph. Star observations, when feasible, allow
  to gather a great deal of information on the instrument performances,
  such as the radiometric performance and the instrument optical point
  spread function (PSF). <P />We report here the first results from the
  above campaign for the two instruments.

Title: Solar Orbiter: connecting remote sensing and in situ
    measurements
Authors: Horbury, T. S.; Auchere, F.; Antonucci, E.; Berghmans, D.;
   Bruno, R.; Carlsson, M.; del Toro Iniesta, J. C.; Fludra, A.; Harra,
   L.; Hassler, D.; Heinzel, P.; Howard, R. A.; Krucker, S.; Livi, S. A.;
   Long, D.; Louarn, P.; Maksimovic, M.; Mueller, D.; Owen, C. J.; Peter,
   H.; Rochus, P. L.; Rodriguez-Pacheco, J.; Romoli, M.; Schühle, U.;
   Solanki, S. K.; Teriaca, L.; Wimmer-Schweingruber, R. F.; Zouganelis,
   Y.; Laker, R.
Bibcode: 2020AGUFMSH038..10H
Altcode:
  A key science goal of the Solar Orbiter mission is to make connections
  between phenomena on the Sun and their manifestations in interplanetary
  space. To that end, the spacecraft carries a carefully tailored
  payload of six remote sensing instruments and four making in situ
  measurements. During June 2020, while the spacecraft was around 0.5
  AU from the Sun, the remote sensing instruments operated for several
  days. While this was primarily an engineering activity, the resulting
  observations provided outstanding measurements and represent the ideal
  first opportunity to investigate the potential for making connections
  between the remote sensing and in situ payloads on Solar Orbiter. <P
  />We present a preliminary analysis of the available remote sensing and
  in situ observations, showing how connections can be made, and discuss
  the potential for further, more precise mapping to be performed as
  the mission progresses.

Title: First Images and Initial In-Flight Performance of the Extreme
    Ultraviolet Imager On-Board Solar Orbiter.
Authors: Auchere, F.; Gissot, S.; Teriaca, L.; Berghmans, D.; Harra,
   L.; Long, D.; Rochus, P. L.; Smith, P.; Schühle, U.; Stegen, K.;
   Aznar Cuadrado, R.; Heerlein, K.; Kraaikamp, E.; Verbeeck, C.
Bibcode: 2020AGUFMSH0360025A
Altcode:
  The Extreme Ultraviolet Imager (EUI) on board Solar Orbiter is
  composed of two High Resolution Imagers working at 121.6 (HRI-LYA,
  H I, chromosphere) and 17.4 nm (HRI-EUV, Fe IX/X, corona) and one
  dual-band Full Sun Imager (FSI) working at 30.4 nm (He II, transition
  region) and 17.4 nm (Fe IX/X, corona). During the commissioning period
  following the launch of Solar Orbiter and two and a half months of
  outgassing, EUI acquired its first solar images on May 12th, 2020 at
  about 0.67 AU. Most of the capabilities of the instrument have been
  tested during the following weeks, which revealed excellent overall
  performance. HRI-EUV already provided images with an angular resolution
  equivalent to ~0.6" (2 pixels) at 1 A.U. HRI-LYA will routinely provide
  images of the Sun at Lyman alpha, which have been otherwise relatively
  rare, with sub-second cadence capability. FSI will provide context for
  connection science but it will also explore regions of the corona never
  imaged before at EUV wavelengths, owing to its 3.8° field of view. EUI
  uses a complex on-board image processing system including advanced
  image compression and event detection algorithms. In particular,
  commissioning tests confirm the good performance of the compression,
  which is critical given the limited total telemetry volume imposed by
  the mission profile. In this paper, we present the main characteristics
  of the first images taken in each channel and we provide an initial
  assessment of the in-flight performance.

Title: First results from combined EUI and SPICE observations of
    Lyman lines of Hydrogen and He II
Authors: Teriaca, L.; Aznar Cuadrado, R.; Giunta, A. S.; Grundy, T.;
   Parenti, S.; Auchere, F.; Vial, J. C.; Fludra, A.; Berghmans, D.;
   Carlsson, M.; Harra, L.; Hassler, D.; Long, D.; Peter, H.; Rochus,
   P. L.; Schühle, U.; Buchlin, E.; Caldwell, M.; Caminade, S.; DeForest,
   C.; Fredvik, T.; Gissot, S.; Heerlein, K.; Janvier, M.; Kraaikamp,
   E.; Kucera, T. A.; Mueller, D.; Schmutz, W. K.; Sidher, S.; Smith, P.;
   Stegen, K.; Thompson, W. T.; Verbeeck, C.; Williams, D.; Young, P. R.
Bibcode: 2020AGUFMSH0360003T
Altcode:
  The Solar Orbiter spacecraft carries a powerful set of remote
  sensing instruments that allow studying the solar atmosphere with
  unprecedented diagnostic capabilities. Many such diagnostics require
  the simultaneous usage of more than one instrument. One example of that
  is the capability, for the first time, to obtain (near) simultaneous
  spatially resolved observations of the emission from the first three
  lines of the Lyman series of hydrogen and of He II Lyman alpha. In fact,
  the SPectral Imaging of the Coronal Environment (SPICE) spectrometer
  can observe the Lyman beta and gamma lines in its long wavelength
  (SPICE-LW) channel, the High Resolution Lyman Alpha (HRI-LYA) telescope
  of the Extreme Ultraviolet Imager (EUI) acquires narrow band images in
  the Lyman alpha line while the Full Disk Imager (FSI) of EUI can take
  images dominated by the Lyman alpha line of ionized Helium at 30.4 nm
  (FSI-304). Being hydrogen and helium the main components of our star,
  these very bright transitions play an important role in the energy
  budget of the outer atmosphere via radiative losses and the measurement
  of their profiles and radiance ratios is a fundamental constraint to
  any comprehensive modelization effort of the upper solar chromosphere
  and transition region. Additionally, monitoring their average ratios
  can serve as a check out for the relative radiometric performance of
  the two instruments throughout the mission. Although the engineering
  data acquired so far are far from ideal in terms of time simultaneity
  (often only within about 1 h) and line coverage (often only Lyman beta
  was acquired by SPICE and not always near simultaneous images from all
  three telescopes are available) the analysis we present here still
  offers a great opportunity to have a first look at the potential of
  this diagnostic from the two instruments. In fact, we have identified
  a series of datasets obtained at disk center and at various positions
  at the solar limb that allow studying the Lyman alpha to beta radiance
  ratio and their relation to He II 30.4 as a function of the position
  on the Sun (disk center versus limb and quiet Sun versus coronal holes).

Title: Very high-resolution observations of the solar atmosphere
    in H I Lyman alpha and Fe IX-X at 17.4 nm as seen by EUI aboard
    Solar Orbiter
Authors: Aznar Cuadrado, R.; Berghmans, D.; Teriaca, L.; Gissot,
   S.; Schühle, U.; Auchere, F.; Harra, L.; Long, D.; Rochus, P. L.;
   Heerlein, K.; Kraaikamp, E.; Smith, P.; Stegen, K.; Verbeeck, C.
Bibcode: 2020AGUFMSH0360026A
Altcode:
  The Extreme Ultraviolet Imager (EUI) aboard Solar Orbiter consists of
  three telescopes, the Full Sun Imager (FSI) and two High Resolution
  Imagers (HRIs). The two HRI telescopes provide images of the base
  of the corona, near to the chromosphere, and of the 1 million K
  corona. In fact, the HRI-EUV telescope operates around 17.4 nm to
  obtain images dominated by emission from lines generated from Fe-IX
  and X ions, formed at about 1 MK, while the HRI-LYA telescope provides
  narrow band images dominated by the H I Lyman alpha line at 121.6 nm,
  formed in the upper chromosphere/lower transition region of the solar
  atmosphere around 20,000 K. Thus, the two imagers provide a powerful
  diagnostics of the solar structural organization, in terms of loop
  hierarchies and connectivity. Here we present an analysis of the first
  two near-simultaneous (within 15s) high-resolution images of the solar
  quiet atmosphere obtained near disk center by the two high-resolution
  telescopes on May 30th 2020, during the commissioning phase of the
  mission , when Solar Orbiter was at about 0.56 AU from the Sun.

Title: Coordination within the remote sensing payload on the Solar
    Orbiter mission
Authors: Auchère, F.; Andretta, V.; Antonucci, E.; Bach, N.;
   Battaglia, M.; Bemporad, A.; Berghmans, D.; Buchlin, E.; Caminade,
   S.; Carlsson, M.; Carlyle, J.; Cerullo, J. J.; Chamberlin, P. C.;
   Colaninno, R. C.; Davila, J. M.; De Groof, A.; Etesi, L.; Fahmy,
   S.; Fineschi, S.; Fludra, A.; Gilbert, H. R.; Giunta, A.; Grundy,
   T.; Haberreiter, M.; Harra, L. K.; Hassler, D. M.; Hirzberger, J.;
   Howard, R. A.; Hurford, G.; Kleint, L.; Kolleck, M.; Krucker, S.;
   Lagg, A.; Landini, F.; Long, D. M.; Lefort, J.; Lodiot, S.; Mampaey,
   B.; Maloney, S.; Marliani, F.; Martinez-Pillet, V.; McMullin, D. R.;
   Müller, D.; Nicolini, G.; Orozco Suarez, D.; Pacros, A.; Pancrazzi,
   M.; Parenti, S.; Peter, H.; Philippon, A.; Plunkett, S.; Rich, N.;
   Rochus, P.; Rouillard, A.; Romoli, M.; Sanchez, L.; Schühle, U.;
   Sidher, S.; Solanki, S. K.; Spadaro, D.; St Cyr, O. C.; Straus, T.;
   Tanco, I.; Teriaca, L.; Thompson, W. T.; del Toro Iniesta, J. C.;
   Verbeeck, C.; Vourlidas, A.; Watson, C.; Wiegelmann, T.; Williams,
   D.; Woch, J.; Zhukov, A. N.; Zouganelis, I.
Bibcode: 2020A&A...642A...6A
Altcode:
  Context. To meet the scientific objectives of the mission, the Solar
  Orbiter spacecraft carries a suite of in-situ (IS) and remote sensing
  (RS) instruments designed for joint operations with inter-instrument
  communication capabilities. Indeed, previous missions have shown that
  the Sun (imaged by the RS instruments) and the heliosphere (mainly
  sampled by the IS instruments) should be considered as an integrated
  system rather than separate entities. Many of the advances expected
  from Solar Orbiter rely on this synergistic approach between IS and
  RS measurements. <BR /> Aims: Many aspects of hardware development,
  integration, testing, and operations are common to two or more
  RS instruments. In this paper, we describe the coordination effort
  initiated from the early mission phases by the Remote Sensing Working
  Group. We review the scientific goals and challenges, and give an
  overview of the technical solutions devised to successfully operate
  these instruments together. <BR /> Methods: A major constraint for the
  RS instruments is the limited telemetry (TM) bandwidth of the Solar
  Orbiter deep-space mission compared to missions in Earth orbit. Hence,
  many of the strategies developed to maximise the scientific return from
  these instruments revolve around the optimisation of TM usage, relying
  for example on onboard autonomy for data processing, compression,
  and selection for downlink. The planning process itself has been
  optimised to alleviate the dynamic nature of the targets, and an
  inter-instrument communication scheme has been implemented which can
  be used to autonomously alter the observing modes. We also outline the
  plans for in-flight cross-calibration, which will be essential to the
  joint data reduction and analysis. <BR /> Results: The RS instrument
  package on Solar Orbiter will carry out comprehensive measurements
  from the solar interior to the inner heliosphere. Thanks to the close
  coordination between the instrument teams and the European Space
  Agency, several challenges specific to the RS suite were identified
  and addressed in a timely manner.

Title: The Solar Orbiter Science Activity Plan. Translating solar
    and heliospheric physics questions into action
Authors: Zouganelis, I.; De Groof, A.; Walsh, A. P.; Williams, D. R.;
   Müller, D.; St Cyr, O. C.; Auchère, F.; Berghmans, D.; Fludra,
   A.; Horbury, T. S.; Howard, R. A.; Krucker, S.; Maksimovic, M.;
   Owen, C. J.; Rodríguez-Pacheco, J.; Romoli, M.; Solanki, S. K.;
   Watson, C.; Sanchez, L.; Lefort, J.; Osuna, P.; Gilbert, H. R.;
   Nieves-Chinchilla, T.; Abbo, L.; Alexandrova, O.; Anastasiadis, A.;
   Andretta, V.; Antonucci, E.; Appourchaux, T.; Aran, A.; Arge, C. N.;
   Aulanier, G.; Baker, D.; Bale, S. D.; Battaglia, M.; Bellot Rubio,
   L.; Bemporad, A.; Berthomier, M.; Bocchialini, K.; Bonnin, X.; Brun,
   A. S.; Bruno, R.; Buchlin, E.; Büchner, J.; Bucik, R.; Carcaboso,
   F.; Carr, R.; Carrasco-Blázquez, I.; Cecconi, B.; Cernuda Cangas, I.;
   Chen, C. H. K.; Chitta, L. P.; Chust, T.; Dalmasse, K.; D'Amicis, R.;
   Da Deppo, V.; De Marco, R.; Dolei, S.; Dolla, L.; Dudok de Wit, T.;
   van Driel-Gesztelyi, L.; Eastwood, J. P.; Espinosa Lara, F.; Etesi,
   L.; Fedorov, A.; Félix-Redondo, F.; Fineschi, S.; Fleck, B.; Fontaine,
   D.; Fox, N. J.; Gandorfer, A.; Génot, V.; Georgoulis, M. K.; Gissot,
   S.; Giunta, A.; Gizon, L.; Gómez-Herrero, R.; Gontikakis, C.; Graham,
   G.; Green, L.; Grundy, T.; Haberreiter, M.; Harra, L. K.; Hassler,
   D. M.; Hirzberger, J.; Ho, G. C.; Hurford, G.; Innes, D.; Issautier,
   K.; James, A. W.; Janitzek, N.; Janvier, M.; Jeffrey, N.; Jenkins,
   J.; Khotyaintsev, Y.; Klein, K. -L.; Kontar, E. P.; Kontogiannis,
   I.; Krafft, C.; Krasnoselskikh, V.; Kretzschmar, M.; Labrosse, N.;
   Lagg, A.; Landini, F.; Lavraud, B.; Leon, I.; Lepri, S. T.; Lewis,
   G. R.; Liewer, P.; Linker, J.; Livi, S.; Long, D. M.; Louarn, P.;
   Malandraki, O.; Maloney, S.; Martinez-Pillet, V.; Martinovic, M.;
   Masson, A.; Matthews, S.; Matteini, L.; Meyer-Vernet, N.; Moraitis,
   K.; Morton, R. J.; Musset, S.; Nicolaou, G.; Nindos, A.; O'Brien,
   H.; Orozco Suarez, D.; Owens, M.; Pancrazzi, M.; Papaioannou, A.;
   Parenti, S.; Pariat, E.; Patsourakos, S.; Perrone, D.; Peter, H.;
   Pinto, R. F.; Plainaki, C.; Plettemeier, D.; Plunkett, S. P.; Raines,
   J. M.; Raouafi, N.; Reid, H.; Retino, A.; Rezeau, L.; Rochus, P.;
   Rodriguez, L.; Rodriguez-Garcia, L.; Roth, M.; Rouillard, A. P.;
   Sahraoui, F.; Sasso, C.; Schou, J.; Schühle, U.; Sorriso-Valvo, L.;
   Soucek, J.; Spadaro, D.; Stangalini, M.; Stansby, D.; Steller, M.;
   Strugarek, A.; Štverák, Š.; Susino, R.; Telloni, D.; Terasa, C.;
   Teriaca, L.; Toledo-Redondo, S.; del Toro Iniesta, J. C.; Tsiropoula,
   G.; Tsounis, A.; Tziotziou, K.; Valentini, F.; Vaivads, A.; Vecchio,
   A.; Velli, M.; Verbeeck, C.; Verdini, A.; Verscharen, D.; Vilmer, N.;
   Vourlidas, A.; Wicks, R.; Wimmer-Schweingruber, R. F.; Wiegelmann,
   T.; Young, P. R.; Zhukov, A. N.
Bibcode: 2020A&A...642A...3Z
Altcode: 2020arXiv200910772Z
  Solar Orbiter is the first space mission observing the solar plasma
  both in situ and remotely, from a close distance, in and out of the
  ecliptic. The ultimate goal is to understand how the Sun produces
  and controls the heliosphere, filling the Solar System and driving
  the planetary environments. With six remote-sensing and four in-situ
  instrument suites, the coordination and planning of the operations are
  essential to address the following four top-level science questions:
  (1) What drives the solar wind and where does the coronal magnetic field
  originate?; (2) How do solar transients drive heliospheric variability?;
  (3) How do solar eruptions produce energetic particle radiation that
  fills the heliosphere?; (4) How does the solar dynamo work and drive
  connections between the Sun and the heliosphere? Maximising the
  mission's science return requires considering the characteristics
  of each orbit, including the relative position of the spacecraft
  to Earth (affecting downlink rates), trajectory events (such
  as gravitational assist manoeuvres), and the phase of the solar
  activity cycle. Furthermore, since each orbit's science telemetry
  will be downloaded over the course of the following orbit, science
  operations must be planned at mission level, rather than at the level
  of individual orbits. It is important to explore the way in which those
  science questions are translated into an actual plan of observations
  that fits into the mission, thus ensuring that no opportunities are
  missed. First, the overarching goals are broken down into specific,
  answerable questions along with the required observations and the
  so-called Science Activity Plan (SAP) is developed to achieve this. The
  SAP groups objectives that require similar observations into Solar
  Orbiter Observing Plans, resulting in a strategic, top-level view of
  the optimal opportunities for science observations during the mission
  lifetime. This allows for all four mission goals to be addressed. In
  this paper, we introduce Solar Orbiter's SAP through a series of
  examples and the strategy being followed.

Title: The Polarimetric and Helioseismic Imager on Solar Orbiter
Authors: Solanki, S. K.; del Toro Iniesta, J. C.; Woch, J.; Gandorfer,
   A.; Hirzberger, J.; Alvarez-Herrero, A.; Appourchaux, T.; Martínez
   Pillet, V.; Pérez-Grande, I.; Sanchis Kilders, E.; Schmidt, W.;
   Gómez Cama, J. M.; Michalik, H.; Deutsch, W.; Fernandez-Rico, G.;
   Grauf, B.; Gizon, L.; Heerlein, K.; Kolleck, M.; Lagg, A.; Meller, R.;
   Müller, R.; Schühle, U.; Staub, J.; Albert, K.; Alvarez Copano, M.;
   Beckmann, U.; Bischoff, J.; Busse, D.; Enge, R.; Frahm, S.; Germerott,
   D.; Guerrero, L.; Löptien, B.; Meierdierks, T.; Oberdorfer, D.;
   Papagiannaki, I.; Ramanath, S.; Schou, J.; Werner, S.; Yang, D.;
   Zerr, A.; Bergmann, M.; Bochmann, J.; Heinrichs, J.; Meyer, S.;
   Monecke, M.; Müller, M. -F.; Sperling, M.; Álvarez García, D.;
   Aparicio, B.; Balaguer Jiménez, M.; Bellot Rubio, L. R.; Cobos
   Carracosa, J. P.; Girela, F.; Hernández Expósito, D.; Herranz, M.;
   Labrousse, P.; López Jiménez, A.; Orozco Suárez, D.; Ramos, J. L.;
   Barandiarán, J.; Bastide, L.; Campuzano, C.; Cebollero, M.; Dávila,
   B.; Fernández-Medina, A.; García Parejo, P.; Garranzo-García, D.;
   Laguna, H.; Martín, J. A.; Navarro, R.; Núñez Peral, A.; Royo, M.;
   Sánchez, A.; Silva-López, M.; Vera, I.; Villanueva, J.; Fourmond,
   J. -J.; de Galarreta, C. Ruiz; Bouzit, M.; Hervier, V.; Le Clec'h,
   J. C.; Szwec, N.; Chaigneau, M.; Buttice, V.; Dominguez-Tagle, C.;
   Philippon, A.; Boumier, P.; Le Cocguen, R.; Baranjuk, G.; Bell,
   A.; Berkefeld, Th.; Baumgartner, J.; Heidecke, F.; Maue, T.; Nakai,
   E.; Scheiffelen, T.; Sigwarth, M.; Soltau, D.; Volkmer, R.; Blanco
   Rodríguez, J.; Domingo, V.; Ferreres Sabater, A.; Gasent Blesa,
   J. L.; Rodríguez Martínez, P.; Osorno Caudel, D.; Bosch, J.; Casas,
   A.; Carmona, M.; Herms, A.; Roma, D.; Alonso, G.; Gómez-Sanjuan, A.;
   Piqueras, J.; Torralbo, I.; Fiethe, B.; Guan, Y.; Lange, T.; Michel,
   H.; Bonet, J. A.; Fahmy, S.; Müller, D.; Zouganelis, I.
Bibcode: 2020A&A...642A..11S
Altcode: 2019arXiv190311061S
  <BR /> Aims: This paper describes the Polarimetric and Helioseismic
  Imager on the Solar Orbiter mission (SO/PHI), the first magnetograph and
  helioseismology instrument to observe the Sun from outside the Sun-Earth
  line. It is the key instrument meant to address the top-level science
  question: How does the solar dynamo work and drive connections between
  the Sun and the heliosphere? SO/PHI will also play an important role
  in answering the other top-level science questions of Solar Orbiter,
  while hosting the potential of a rich return in further science. <BR
  /> Methods: SO/PHI measures the Zeeman effect and the Doppler shift
  in the Fe I 617.3 nm spectral line. To this end, the instrument
  carries out narrow-band imaging spectro-polarimetry using a tunable
  LiNbO<SUB>3</SUB> Fabry-Perot etalon, while the polarisation modulation
  is done with liquid crystal variable retarders. The line and the nearby
  continuum are sampled at six wavelength points and the data are recorded
  by a 2k × 2k CMOS detector. To save valuable telemetry, the raw data
  are reduced on board, including being inverted under the assumption of
  a Milne-Eddington atmosphere, although simpler reduction methods are
  also available on board. SO/PHI is composed of two telescopes; one,
  the Full Disc Telescope, covers the full solar disc at all phases of
  the orbit, while the other, the High Resolution Telescope, can resolve
  structures as small as 200 km on the Sun at closest perihelion. The high
  heat load generated through proximity to the Sun is greatly reduced by
  the multilayer-coated entrance windows to the two telescopes that allow
  less than 4% of the total sunlight to enter the instrument, most of
  it in a narrow wavelength band around the chosen spectral line. <BR />
  Results: SO/PHI was designed and built by a consortium having partners
  in Germany, Spain, and France. The flight model was delivered to
  Airbus Defence and Space, Stevenage, and successfully integrated into
  the Solar Orbiter spacecraft. A number of innovations were introduced
  compared with earlier space-based spectropolarimeters, thus allowing
  SO/PHI to fit into the tight mass, volume, power and telemetry budgets
  provided by the Solar Orbiter spacecraft and to meet the (e.g. thermal)
  challenges posed by the mission's highly elliptical orbit.

Title: The Solar Orbiter SPICE instrument. An extreme UV imaging
    spectrometer
Authors: SPICE Consortium; Anderson, M.; Appourchaux, T.; Auchère, F.;
   Aznar Cuadrado, R.; Barbay, J.; Baudin, F.; Beardsley, S.; Bocchialini,
   K.; Borgo, B.; Bruzzi, D.; Buchlin, E.; Burton, G.; Büchel, V.;
   Caldwell, M.; Caminade, S.; Carlsson, M.; Curdt, W.; Davenne, J.;
   Davila, J.; Deforest, C. E.; Del Zanna, G.; Drummond, D.; Dubau,
   J.; Dumesnil, C.; Dunn, G.; Eccleston, P.; Fludra, A.; Fredvik, T.;
   Gabriel, A.; Giunta, A.; Gottwald, A.; Griffin, D.; Grundy, T.; Guest,
   S.; Gyo, M.; Haberreiter, M.; Hansteen, V.; Harrison, R.; Hassler,
   D. M.; Haugan, S. V. H.; Howe, C.; Janvier, M.; Klein, R.; Koller,
   S.; Kucera, T. A.; Kouliche, D.; Marsch, E.; Marshall, A.; Marshall,
   G.; Matthews, S. A.; McQuirk, C.; Meining, S.; Mercier, C.; Morris,
   N.; Morse, T.; Munro, G.; Parenti, S.; Pastor-Santos, C.; Peter, H.;
   Pfiffner, D.; Phelan, P.; Philippon, A.; Richards, A.; Rogers, K.;
   Sawyer, C.; Schlatter, P.; Schmutz, W.; Schühle, U.; Shaughnessy,
   B.; Sidher, S.; Solanki, S. K.; Speight, R.; Spescha, M.; Szwec, N.;
   Tamiatto, C.; Teriaca, L.; Thompson, W.; Tosh, I.; Tustain, S.; Vial,
   J. -C.; Walls, B.; Waltham, N.; Wimmer-Schweingruber, R.; Woodward,
   S.; Young, P.; de Groof, A.; Pacros, A.; Williams, D.; Müller, D.
Bibcode: 2020A&A...642A..14S
Altcode: 2019arXiv190901183A; 2019arXiv190901183S
  <BR /> Aims: The Spectral Imaging of the Coronal Environment (SPICE)
  instrument is a high-resolution imaging spectrometer operating at
  extreme ultraviolet wavelengths. In this paper, we present the concept,
  design, and pre-launch performance of this facility instrument on the
  ESA/NASA Solar Orbiter mission. <BR /> Methods: The goal of this paper
  is to give prospective users a better understanding of the possible
  types of observations, the data acquisition, and the sources that
  contribute to the instrument's signal. <BR /> Results: The paper
  discusses the science objectives, with a focus on the SPICE-specific
  aspects, before presenting the instrument's design, including optical,
  mechanical, thermal, and electronics aspects. This is followed by a
  characterisation and calibration of the instrument's performance. The
  paper concludes with descriptions of the operations concept and data
  processing. <BR /> Conclusions: The performance measurements of the
  various instrument parameters meet the requirements derived from the
  mission's science objectives. The SPICE instrument is ready to perform
  measurements that will provide vital contributions to the scientific
  success of the Solar Orbiter mission.

Title: The Solar Orbiter mission. Science overview
Authors: Müller, D.; St. Cyr, O. C.; Zouganelis, I.; Gilbert, H. R.;
   Marsden, R.; Nieves-Chinchilla, T.; Antonucci, E.; Auchère, F.;
   Berghmans, D.; Horbury, T. S.; Howard, R. A.; Krucker, S.; Maksimovic,
   M.; Owen, C. J.; Rochus, P.; Rodriguez-Pacheco, J.; Romoli, M.;
   Solanki, S. K.; Bruno, R.; Carlsson, M.; Fludra, A.; Harra, L.;
   Hassler, D. M.; Livi, S.; Louarn, P.; Peter, H.; Schühle, U.;
   Teriaca, L.; del Toro Iniesta, J. C.; Wimmer-Schweingruber, R. F.;
   Marsch, E.; Velli, M.; De Groof, A.; Walsh, A.; Williams, D.
Bibcode: 2020A&A...642A...1M
Altcode: 2020arXiv200900861M
  <BR /> Aims: Solar Orbiter, the first mission of ESA's Cosmic Vision
  2015-2025 programme and a mission of international collaboration between
  ESA and NASA, will explore the Sun and heliosphere from close up and
  out of the ecliptic plane. It was launched on 10 February 2020 04:03
  UTC from Cape Canaveral and aims to address key questions of solar and
  heliospheric physics pertaining to how the Sun creates and controls
  the Heliosphere, and why solar activity changes with time. To answer
  these, the mission carries six remote-sensing instruments to observe
  the Sun and the solar corona, and four in-situ instruments to measure
  the solar wind, energetic particles, and electromagnetic fields. In
  this paper, we describe the science objectives of the mission, and how
  these will be addressed by the joint observations of the instruments
  onboard. <BR /> Methods: The paper first summarises the mission-level
  science objectives, followed by an overview of the spacecraft and
  payload. We report the observables and performance figures of each
  instrument, as well as the trajectory design. This is followed by a
  summary of the science operations concept. The paper concludes with a
  more detailed description of the science objectives. <BR /> Results:
  Solar Orbiter will combine in-situ measurements in the heliosphere
  with high-resolution remote-sensing observations of the Sun to address
  fundamental questions of solar and heliospheric physics. The performance
  of the Solar Orbiter payload meets the requirements derived from the
  mission's science objectives. Its science return will be augmented
  further by coordinated observations with other space missions and
  ground-based observatories. <P />ARRAY(0x207ce98)

Title: The Solar Orbiter EUI instrument: The Extreme Ultraviolet
    Imager
Authors: Rochus, P.; Auchère, F.; Berghmans, D.; Harra, L.; Schmutz,
   W.; Schühle, U.; Addison, P.; Appourchaux, T.; Aznar Cuadrado,
   R.; Baker, D.; Barbay, J.; Bates, D.; BenMoussa, A.; Bergmann, M.;
   Beurthe, C.; Borgo, B.; Bonte, K.; Bouzit, M.; Bradley, L.; Büchel,
   V.; Buchlin, E.; Büchner, J.; Cabé, F.; Cadiergues, L.; Chaigneau,
   M.; Chares, B.; Choque Cortez, C.; Coker, P.; Condamin, M.; Coumar,
   S.; Curdt, W.; Cutler, J.; Davies, D.; Davison, G.; Defise, J. -M.;
   Del Zanna, G.; Delmotte, F.; Delouille, V.; Dolla, L.; Dumesnil, C.;
   Dürig, F.; Enge, R.; François, S.; Fourmond, J. -J.; Gillis, J. -M.;
   Giordanengo, B.; Gissot, S.; Green, L. M.; Guerreiro, N.; Guilbaud,
   A.; Gyo, M.; Haberreiter, M.; Hafiz, A.; Hailey, M.; Halain, J. -P.;
   Hansotte, J.; Hecquet, C.; Heerlein, K.; Hellin, M. -L.; Hemsley, S.;
   Hermans, A.; Hervier, V.; Hochedez, J. -F.; Houbrechts, Y.; Ihsan,
   K.; Jacques, L.; Jérôme, A.; Jones, J.; Kahle, M.; Kennedy, T.;
   Klaproth, M.; Kolleck, M.; Koller, S.; Kotsialos, E.; Kraaikamp, E.;
   Langer, P.; Lawrenson, A.; Le Clech', J. -C.; Lenaerts, C.; Liebecq,
   S.; Linder, D.; Long, D. M.; Mampaey, B.; Markiewicz-Innes, D.;
   Marquet, B.; Marsch, E.; Matthews, S.; Mazy, E.; Mazzoli, A.; Meining,
   S.; Meltchakov, E.; Mercier, R.; Meyer, S.; Monecke, M.; Monfort,
   F.; Morinaud, G.; Moron, F.; Mountney, L.; Müller, R.; Nicula, B.;
   Parenti, S.; Peter, H.; Pfiffner, D.; Philippon, A.; Phillips, I.;
   Plesseria, J. -Y.; Pylyser, E.; Rabecki, F.; Ravet-Krill, M. -F.;
   Rebellato, J.; Renotte, E.; Rodriguez, L.; Roose, S.; Rosin, J.;
   Rossi, L.; Roth, P.; Rouesnel, F.; Roulliay, M.; Rousseau, A.; Ruane,
   K.; Scanlan, J.; Schlatter, P.; Seaton, D. B.; Silliman, K.; Smit,
   S.; Smith, P. J.; Solanki, S. K.; Spescha, M.; Spencer, A.; Stegen,
   K.; Stockman, Y.; Szwec, N.; Tamiatto, C.; Tandy, J.; Teriaca, L.;
   Theobald, C.; Tychon, I.; van Driel-Gesztelyi, L.; Verbeeck, C.;
   Vial, J. -C.; Werner, S.; West, M. J.; Westwood, D.; Wiegelmann, T.;
   Willis, G.; Winter, B.; Zerr, A.; Zhang, X.; Zhukov, A. N.
Bibcode: 2020A&A...642A...8R
Altcode:
  Context. The Extreme Ultraviolet Imager (EUI) is part of the remote
  sensing instrument package of the ESA/NASA Solar Orbiter mission
  that will explore the inner heliosphere and observe the Sun from
  vantage points close to the Sun and out of the ecliptic. Solar Orbiter
  will advance the "connection science" between solar activity and the
  heliosphere. <BR /> Aims: With EUI we aim to improve our understanding
  of the structure and dynamics of the solar atmosphere, globally as well
  as at high resolution, and from high solar latitude perspectives. <BR />
  Methods: The EUI consists of three telescopes, the Full Sun Imager and
  two High Resolution Imagers, which are optimised to image in Lyman-α
  and EUV (17.4 nm, 30.4 nm) to provide a coverage from chromosphere
  up to corona. The EUI is designed to cope with the strong constraints
  imposed by the Solar Orbiter mission characteristics. Limited telemetry
  availability is compensated by state-of-the-art image compression,
  onboard image processing, and event selection. The imposed power
  limitations and potentially harsh radiation environment necessitate
  the use of novel CMOS sensors. As the unobstructed field of view of
  the telescopes needs to protrude through the spacecraft's heat shield,
  the apertures have been kept as small as possible, without compromising
  optical performance. This led to a systematic effort to optimise the
  throughput of every optical element and the reduction of noise levels
  in the sensor. <BR /> Results: In this paper we review the design
  of the two elements of the EUI instrument: the Optical Bench System
  and the Common Electronic Box. Particular attention is also given to
  the onboard software, the intended operations, the ground software,
  and the foreseen data products. <BR /> Conclusions: The EUI will
  bring unique science opportunities thanks to its specific design,
  its viewpoint, and to the planned synergies with the other Solar
  Orbiter instruments. In particular, we highlight science opportunities
  brought by the out-of-ecliptic vantage point of the solar poles,
  the high-resolution imaging of the high chromosphere and corona,
  and the connection to the outer corona as observed by coronagraphs.

Title: Metis: the Solar Orbiter visible light and ultraviolet
    coronal imager
Authors: Antonucci, Ester; Romoli, Marco; Andretta, Vincenzo; Fineschi,
   Silvano; Heinzel, Petr; Moses, J. Daniel; Naletto, Giampiero; Nicolini,
   Gianalfredo; Spadaro, Daniele; Teriaca, Luca; Berlicki, Arkadiusz;
   Capobianco, Gerardo; Crescenzio, Giuseppe; Da Deppo, Vania; Focardi,
   Mauro; Frassetto, Fabio; Heerlein, Klaus; Landini, Federico; Magli,
   Enrico; Marco Malvezzi, Andrea; Massone, Giuseppe; Melich, Radek;
   Nicolosi, Piergiorgio; Noci, Giancarlo; Pancrazzi, Maurizio; Pelizzo,
   Maria G.; Poletto, Luca; Sasso, Clementina; Schühle, Udo; Solanki,
   Sami K.; Strachan, Leonard; Susino, Roberto; Tondello, Giuseppe;
   Uslenghi, Michela; Woch, Joachim; Abbo, Lucia; Bemporad, Alessandro;
   Casti, Marta; Dolei, Sergio; Grimani, Catia; Messerotti, Mauro;
   Ricci, Marco; Straus, Thomas; Telloni, Daniele; Zuppella, Paola;
   Auchère, Frederic; Bruno, Roberto; Ciaravella, Angela; Corso,
   Alain J.; Alvarez Copano, Miguel; Aznar Cuadrado, Regina; D'Amicis,
   Raffaella; Enge, Reiner; Gravina, Alessio; Jejčič, Sonja; Lamy,
   Philippe; Lanzafame, Alessandro; Meierdierks, Thimo; Papagiannaki,
   Ioanna; Peter, Hardi; Fernandez Rico, German; Giday Sertsu, Mewael;
   Staub, Jan; Tsinganos, Kanaris; Velli, Marco; Ventura, Rita; Verroi,
   Enrico; Vial, Jean-Claude; Vives, Sebastien; Volpicelli, Antonio;
   Werner, Stephan; Zerr, Andreas; Negri, Barbara; Castronuovo, Marco;
   Gabrielli, Alessandro; Bertacin, Roberto; Carpentiero, Rita; Natalucci,
   Silvia; Marliani, Filippo; Cesa, Marco; Laget, Philippe; Morea, Danilo;
   Pieraccini, Stefano; Radaelli, Paolo; Sandri, Paolo; Sarra, Paolo;
   Cesare, Stefano; Del Forno, Felice; Massa, Ernesto; Montabone, Mauro;
   Mottini, Sergio; Quattropani, Daniele; Schillaci, Tiziano; Boccardo,
   Roberto; Brando, Rosario; Pandi, Arianna; Baietto, Cristian; Bertone,
   Riccardo; Alvarez-Herrero, Alberto; García Parejo, Pilar; Cebollero,
   María; Amoruso, Mauro; Centonze, Vito
Bibcode: 2020A&A...642A..10A
Altcode: 2019arXiv191108462A
  <BR /> Aims: Metis is the first solar coronagraph designed for a
  space mission and is capable of performing simultaneous imaging of the
  off-limb solar corona in both visible and UV light. The observations
  obtained with Metis aboard the Solar Orbiter ESA-NASA observatory
  will enable us to diagnose, with unprecedented temporal coverage and
  spatial resolution, the structures and dynamics of the full corona
  in a square field of view (FoV) of ±2.9° in width, with an inner
  circular FoV at 1.6°, thus spanning the solar atmosphere from 1.7
  R<SUB>⊙</SUB> to about 9 R<SUB>⊙</SUB>, owing to the eccentricity
  of the spacecraft orbit. Due to the uniqueness of the Solar Orbiter
  mission profile, Metis will be able to observe the solar corona
  from a close (0.28 AU, at the closest perihelion) vantage point,
  achieving increasing out-of-ecliptic views with the increase of the
  orbit inclination over time. Moreover, observations near perihelion,
  during the phase of lower rotational velocity of the solar surface
  relative to the spacecraft, allow longer-term studies of the off-limb
  coronal features, thus finally disentangling their intrinsic evolution
  from effects due to solar rotation. <BR /> Methods: Thanks to a novel
  occultation design and a combination of a UV interference coating of
  the mirrors and a spectral bandpass filter, Metis images the solar
  corona simultaneously in the visible light band, between 580 and 640
  nm, and in the UV H I Lyman-α line at 121.6 nm. The visible light
  channel also includes a broadband polarimeter able to observe the
  linearly polarised component of the K corona. The coronal images in
  both the UV H I Lyman-α and polarised visible light are obtained at
  high spatial resolution with a spatial scale down to about 2000 km
  and 15 000 km at perihelion, in the cases of the visible and UV light,
  respectively. A temporal resolution down to 1 s can be achieved when
  observing coronal fluctuations in visible light. <BR /> Results: The
  Metis measurements, obtained from different latitudes, will allow for
  complete characterisation of the main physical parameters and dynamics
  of the electron and neutral hydrogen/proton plasma components of the
  corona in the region where the solar wind undergoes the acceleration
  process and where the onset and initial propagation of coronal mass
  ejections (CMEs) take place. The near-Sun multi-wavelength coronal
  imaging performed with Metis, combined with the unique opportunities
  offered by the Solar Orbiter mission, can effectively address crucial
  issues of solar physics such as: the origin and heating/acceleration
  of the fast and slow solar wind streams; the origin, acceleration,
  and transport of the solar energetic particles; and the transient
  ejection of coronal mass and its evolution in the inner heliosphere,
  thus significantly improving our understanding of the region connecting
  the Sun to the heliosphere and of the processes generating and driving
  the solar wind and coronal mass ejections. <BR /> Conclusions: This
  paper presents the scientific objectives and requirements, the overall
  optical design of the Metis instrument, the thermo-mechanical design,
  and the processing and power unit; reports on the results of the
  campaigns dedicated to integration, alignment, and tests, and to
  the characterisation of the instrument performance; describes the
  operation concept, data handling, and software tools; and, finally,
  the diagnostic techniques to be applied to the data, as well as a brief
  description of the expected scientific products. The performance of the
  instrument measured during calibrations ensures that the scientific
  objectives of Metis can be pursued with success. <P />Metis website:
  <A href="http://metis.oato.inaf.it">http://metis.oato.inaf.it</A>

Title: Optical design of the multi-wavelength imaging coronagraph
    Metis for the solar orbiter mission
Authors: Fineschi, S.; Naletto, G.; Romoli, M.; Da Deppo, V.;
   Antonucci, E.; Moses, D.; Malvezzi, A. M.; Nicolini, G.; Spadaro,
   D.; Teriaca, L.; Andretta, V.; Capobianco, G.; Crescenzio, G.;
   Focardi, M.; Frassetto, F.; Landini, F.; Massone, G.; Melich, R.;
   Nicolosi, P.; Pancrazzi, M.; Pelizzo, M. G.; Poletto, L.; Schühle,
   U.; Uslenghi, M.; Vives, S.; Solanki, S. K.; Heinzel, P.; Berlicki,
   A.; Cesare, S.; Morea, D.; Mottini, S.; Sandri, P.; Alvarez-Herrero,
   A.; Castronuovo, M.
Bibcode: 2020ExA....49..239F
Altcode: 2020ExA...tmp...14F
  This paper describes the innovative optical design of the Metis
  coronagraph for the Solar Orbiter ESA-NASA mission. Metis is a
  multi-wavelength, externally occulted telescope for the imaging
  of the solar corona in both the visible and ultraviolet wavelength
  ranges. Metis adopts a novel occultation scheme for the solar disk,
  that we named "inverse external occulter", for reducing the extremely
  high thermal load on the instrument at the spacecraft perihelion. The
  core of the Metis optical design is an aplanatic Gregorian telescope
  common to both the visible and ultraviolet channels. A suitable
  dichroic beam-splitter, optimized for transmitting a narrow-band in
  the ultraviolet (121.6 nm, HI Lyman-α) and reflecting a broadband
  in the visible (580-640 nm) spectral range, is used to separate the
  two optical paths. Along the visible light optical path, a liquid
  crystal electro-optical modulator, used for the first time in space,
  allows making polarimetric measurements.

Title: The Solar Orbiter EUI instrument: The Extreme Ultraviolet
    Imager
Authors: Rochus, P. L.; Auchere, F.; Berghmans, D.; Harra, L.; Schmutz,
   W. K.; Schühle, U.
Bibcode: 2019AGUFMSH21D3291R
Altcode:
  The Extreme Ultraviolet Imager (EUI) is part of the remote sensing
  instrument package of the ESA/NASA Solar Orbiter mission that will
  explore the inner heliosphere and observe the Sun from vantage points
  close to the Sun and out-of-the-ecliptic. <P />EUI aims at improving our
  understanding of the structure and dynamics of the solar atmosphere. EUI
  will take images of the solar atmosphere, globally as well as at high
  resolution, and from high solar latitude perspectives. <P />EUI consists
  of 3 telescopes that are optimized to image in Lyman-a and EUV 17.4nm
  and 30.4 nm to provide a coverage from chromosphere up to corona. EUI
  is designed to cope with the strong constraints that Solar Orbiter has
  as a deep space mission. Limited telemetry availability is compensated
  by state-of-the-art image compression, on board image processing and
  event selection. The imposed power limitations and potentially harsh
  radiation environment lead to the usage of novel CMOS sensors. As
  the unobstructed field of view of the telescopes needs to protrude
  through the spacecraft heat shield, the apertures were kept as small as
  possible. This lead to a systematic effort to optimize the throughput
  of every optical element and the reduction of noise levels in the
  sensor. <P />In this paper we review the design of the two elements of
  the EUI instrument: the Optical Bench System and the Common Electronic
  Box. Particular attention is also given to the on board software,
  the intended operations, the ground software and the foreseen data
  products. <P />EUI will bring unique science opportunities thanks to its
  specific design, its viewpoint and thanks to the planned synergies with
  the other Solar Orbiter instruments. We highlight in particular science
  opportunities brought by the out-of-ecliptic vantage point of the solar
  poles, the high resolution imaging of the high chromosphere and corona,
  and the connection to the outer corona as observed by coronagraphs.

Title: The Solar-C_EUVST mission
Authors: Shimizu, Toshifumi; Imada, Shinsuke; Kawate, Tomoko;
   Ichimoto, Kiyoshi; Suematsu, Yoshinori; Hara, Hirohisa; Katsukawa,
   Yukio; Kubo, Masahito; Toriumi, Shin; Watanabe, Tetsuya; Yokoyama,
   Takaaki; Korendyke, Clarence M.; Warren, Harry P.; Tarbell, Ted; De
   Pontieu, Bart; Teriaca, Luca; Schühle, Udo H.; Solanki, Sami; Harra,
   Louise K.; Matthews, Sarah; Fludra, A.; Auchère, F.; Andretta, V.;
   Naletto, G.; Zhukov, A.
Bibcode: 2019SPIE11118E..07S
Altcode:
  Solar-C EUVST (EUV High-Throughput Spectroscopic Telescope) is a
  solar physics mission concept that was selected as a candidate for
  JAXA competitive M-class missions in July 2018. The onboard science
  instrument, EUVST, is an EUV spectrometer with slit-jaw imaging
  system that will simultaneously observe the solar atmosphere from the
  photosphere/chromosphere up to the corona with seamless temperature
  coverage, high spatial resolution, and high throughput for the first
  time. The mission is designed to provide a conclusive answer to the
  most fundamental questions in solar physics: how fundamental processes
  lead to the formation of the solar atmosphere and the solar wind, and
  how the solar atmosphere becomes unstable, releasing the energy that
  drives solar flares and eruptions. The entire instrument structure
  and the primary mirror assembly with scanning and tip-tilt fine
  pointing capability for the EUVST are being developed in Japan, with
  spectrograph and slit-jaw imaging hardware and science contributions
  from US and European countries. The mission will be launched and
  installed in a sun-synchronous polar orbit by a JAXA Epsilon vehicle in
  2025. ISAS/JAXA coordinates the conceptual study activities during the
  current mission definition phase in collaboration with NAOJ and other
  universities. The team is currently working towards the JAXA final
  down-selection expected at the end of 2019, with strong support from
  US and European colleagues. The paper provides an overall description
  of the mission concept, key technologies, and the latest status.

Title: Optical alignment of the Solar Orbiter EUI flight instrument
Authors: Mazzoli, A.; Halain, J. -P.; Auchère, F.; Barbay, J.;
   Meining, S.; Philippon, A.; Morinaud, G.; Roose, S.; Hellin, M. -L.;
   Jacques, L.; Schühle, U.; Dumesnil, C.; Mercier, R.; Renotte, E.;
   Rochus, P.
Bibcode: 2019SPIE11180E..1OM
Altcode:
  The Extreme Ultraviolet Imager (EUI) instrument for the Solar Orbiter
  mission will image the solar corona in the extreme ultraviolet
  (17.1 nm and 30.4 nm) and in the vacuum ultraviolet (121.6 nm). It
  is composed of three channels, each one containing a telescope. Two
  of these channels are high resolution imagers (HRI) at respectively
  17.1 nm (HRI-EUV) and 121.6 nm (HRI-Ly ), each one composed of two
  off-axis aspherical mirrors. The third channel is a full sun imager
  (FSI) composed of one single off-axis aspherical mirror and working
  at 17.1 nm and 30.4 nm alternatively. This paper presents the optical
  alignment of each telescope. The alignment process involved a set of
  Optical Ground Support Equipment (OGSE) such as theodolites, laser
  tracker, visible-light interferometer as well as a 3D Coordinates
  Measuring Machine (CMM). The mirrors orientation have been measured
  with respect to reference alignment cubes using theodolites. Their
  positions with respect to reference pins on the instrument optical
  bench have been measured using the 3D CMM. The mirrors orientations and
  positions have been adjusted by shimming of the mirrors mount during
  the alignment process. After this mechanical alignment, the quality
  of the wavefront has been checked by interferometric measurements,
  in an iterative process with the orientation and position adjustment
  to achieve the required image quality.

Title: Optical performance of the Metis coronagraph on the Solar
    Orbiter ESA mission
Authors: Frassetto, Fabio; Da Deppo, Vania; Zuppella, Paola; Romoli,
   Marco; Fineschi, Silvano; Antonucci, Ester; Nicolini, Giana; Naletto,
   Giampiero; Nicolosi, Piergiorgio; Spadaro, Daniele; Andretta, Vincenzo;
   Castronuovo, Marco; Casti, Marta; Capobianco, Gerardo; Massone,
   Giuseppe; Susino, Roberto; Landini, Federico; Pancrazzi, Maurizio;
   Teriaca, Luca; Schühle, Udo; Heerlein, Klaus; Uslenghi, Michela
Bibcode: 2019SPIE11180E..6YF
Altcode:
  The Metis coronagraph aboard the Solar Orbiter ESA spacecraft is
  expected to provide new insights into the solar dynamics. In detail,
  it is designed to address three main questions: the energy deposition
  mechanism at the poles (where the fast wind is originated), the
  source of the slow wind at lower altitude, and how the global corona
  evolves, in particular in relation to the huge plasma ejections that
  occasionally are produced. To obtain the required optical performance,
  not only the Metis optical design has been highly optimized, but the
  alignment procedure has also been subjected to an accurate evaluation
  in order to fulfill the integration specifications. The telescope
  assembling sequence has been constructed considering all the subsystems
  manufacturing, alignment and integration tolerances. The performance
  verification activity is an important milestone in the instrument
  characterization and the obtained results will assure the fulfillment
  of the science requirements for its operation in space. The entire
  alignment and verification phase has been performed by the Metis team in
  collaboration with Thales Alenia Space Torino and took place in ALTEC
  (Turin) at the Optical Payload System Facility using the Space Optics
  Calibration Chamber infrastructure, a vacuum chamber especially built
  and tested for the alignment and calibration of the Metis coronagraph,
  and suitable for tests of future payloads. The goal of the alignment,
  integration, verification and calibration processes is to measure
  the parameters of the telescope, and the characteristics of the two
  Metis channels: visible and ultraviolet. They work in parallel thanks
  to the peculiar optical layout. The focusing and alignment performance
  of the two channels must be well understood, and the results need to be
  easily compared to the requirements. For this, a dedicated illumination
  method, with both channels fed by the same source, has been developed;
  and a procedure to perform a simultaneous through focus analysis has
  been adopted. In this paper the final optical performance achieved by
  Metis is reported and commented.

Title: Stray light calibration for the Solar Orbiter/Metis solar
    coronagraph
Authors: Landini, F.; Romoli, M.; Fineschi, S.; Casini, C.; Baccani,
   C.; Antonucci, E.; Nicolini, G.; Naletto, G.; Nicolosi, P.; Spadaro,
   D.; Andretta, V.; Castronuovo, M.; Casti, M.; Capobianco, G.; Massone,
   G.; Susino, R.; Da Deppo, V.; Frassetto, F.; Pancrazzi, M.; Teriaca,
   L.; Schuehle, U.; Heerlein, K.; Uslenghi, M.
Bibcode: 2019SPIE11180E..2IL
Altcode:
  The Solar Orbiter/Metis visible and UV solar coronagraph redefines
  the concept of external occultation in solar coronagraphy. Classical
  externally occulted coronagraphs are characterized by an occulter in
  front of the telescope entrance aperture. Solar Orbiter will approach
  the Sun down to 0.28 AU: in order to reduce the thermal load, the
  Metis design switches the positions of the entrance aperture and the
  external occulter thus achieving what is called the inverted external
  occultation. The inverted external occulter (IEO) consists of a circular
  aperture on the Solar Orbiter thermal shield that acts as coronagraph
  entrance pupil. A spherical mirror, located 800 mm behind the IEO, back
  rejects the disklight through the IEO itself. To pursue the goal of
  maximizing the reduction of the stray light level on the focal plane,
  an optimization of the IEO shape was implemented. The stray light
  calibration was performed in a clean environment in front of the OPSys
  solar disk divergence simulator (at ALTEC, in Torino, Italy), which is
  able to emulate different heliocentric distances. Ground calibrations
  were a unique opportunity to map the Metis stray light level thanks to
  a pure solar disk simulator without the solar corona. The stray light
  calibration was limited to the visible light case, being the most
  stringent. This work is focused on the description of the laboratory
  facility that was used to perform the stray light calibration and on
  the calibration results.

Title: The EUI instrument onboard Solar Orbiter: the EUV corona
    imaged differently
Authors: Berghmans, David; Rochus, Pierre; Auchère, Frédéric;
   Harra, Louise; Schmutz, Werner; Schühle, Udo
Bibcode: 2018csc..confE..73B
Altcode:
  The ESA Solar Orbiter mission is designed to determine how the Sun
  creates and controls the heliosphere. The spacecraft will bring
  a combination of in situ and remote sensing instruments out of the
  ecliptic (&gt;30°) and close to the sun (0.3 solar-radii). The launch
  of Solar Orbiter is expected (not earlier than) Feb 2019. The Extreme
  Ultraviolet Imager is part of the remote-sensing package of Solar
  Orbiter, to be operating during 3 ten-day periods of each orbit around
  the Sun, which last roughly half a year. These 3 periods will correspond
  to perihelion and maximal solar latitude north and south. The Extreme
  Ultraviolet Imager is itself a suite of three UV and EUV telescopes
  that observe the solar atmosphere both globally as well as at very
  high resolution. The two high-resolution imagers (HRIs) will image the
  solar atmosphere in the chromospheric Lyman alpha line and the coronal
  17nm pass band with a resolution of 0.5 arcsec. From perihelion, this
  will correspond to a pixel footprint on the solar disc of (110km)^2
  . The Full Sun Imager (FSI), working at the 17.4 nm and 30.4 nm EUV
  passbands, will provide a global view of the solar atmosphere and is
  therefore an essential building block for the "connection science"
  of the Solar Orbiter mission. The FSI field of view is large enough
  (228arcmin) that, even at perihelion and at maximal off-points by Solar
  Orbiter, the full solar disk remains in the field of view. This large
  FOV and the FSI's high sensitivity will allow to image the "transition
  corona" where the topology of streamers and pseudo-streamers fades in
  the solar wind. Furthermore, FSI will be the first to image all this
  from out of the ecliptic. In this talk we will give an overview of the
  EUI instrument. We will focus on the novel aspects of EUI that will
  allow it to image beyond what previous EUV imagers could show us: EUV
  imaging from the highest solar latitude, with the widest field-of-view
  and at highest spatial resolution.

Title: Broadband EUV/FUV mirror coatings for a solar spectrograph
    mission
Authors: Teriaca, Luca; Feigl, Torsten; Schühle, Udo
Bibcode: 2018SPIE10699E..2YT
Altcode:
  As it is rich in spectral lines emitted by plasma between 10000 K
  and 20 MK, the vacuum ultraviolet (VUV - 17 to 200 nm) solar spectrum
  is extremely valuable for instruments that study the physics of the
  solar atmosphere. We present multilayer coatings with simultaneous
  broadband reflectance in the two spectral ranges of 16.9 nm to 21.5 nm
  and 46.3 nm to 127.5 nm. The coatings are based on Mo/Si multilayers
  with a thin capping layer of boron carbide (B<SUB>4</SUB>C). Samples
  were produced and their reflectance measured. Their performance in
  terms of resistance to high temperatures and low micro-roughness was
  also assessed by measurement. Our study shows that a coating with the
  characteristics required by next generation spectrometers for studies
  of the solar atmosphere is feasible.

Title: The solar orbiter Metis and EUI intensified CMOS-APS detectors:
    concept, main characteristics, and performance
Authors: Schühle, Udo; Teriaca, Luca; Aznar Cuadrado, Regina;
   Heerlein, Klaus; Uslenghi, Michela; Werner, Stephan
Bibcode: 2018SPIE10699E..34S
Altcode:
  Two instruments aboard the Solar Orbiter mission, the Extreme
  Ultraviolet Imager and the Metis coronagraph, are using cameras of
  similar design to obtain images in the Lyman alpha line of hydrogen
  at 121.6 nm. Each of these cameras is based on an APS sensor used
  as readout of a single microchannel plate intensifier unit whose
  output current is converted into visible light photons through a
  phosphor screen. Before integration on the respective instruments, both
  detector's flight models have been characterized and calibrated. In this
  paper, we describe the two camera systems, the results of qualification
  tests, and report their performance characteristics.

Title: The EUI flight instrument of Solar Orbiter: from optical
    alignment to end-to-end calibration
Authors: Halain, J. -P.; Renotte, E.; Auchère, F.; Berghmans, D.;
   Delmotte, F.; Harra, L.; Schmutz, W.; Schühle, U.; Aznar Cuadrado,
   R.; Dumesnil, C.; Gyo, M.; Kennedy, T.; Verbeeck, C.; Barbay, J.;
   Giordanengo, B.; Gissot, S.; Gottwald, A.; Heerlein, K.; Hellin,
   M. -L.; Hermans, A.; Hervier, V.; Jacques, L.; Laubis, C.; Mazzoli,
   A.; Meining, S.; Mercier, R.; Philippon, A.; Roose, S.; Rossi, L.;
   Scholze, F.; Smith, P.; Teriaca, L.; Zhang, X.; Rochus, P.
Bibcode: 2018SPIE10699E..0HH
Altcode:
  The Extreme Ultraviolet Imager (EUI) instrument for the Solar Orbiter
  mission will image the solar corona in the extreme ultraviolet (17.1
  nm and 30.4 nm) and in the vacuum ultraviolet (121.6 nm) spectral
  ranges. The development of the EUI instrument has been successfully
  completed with the optical alignment of its three channels' telescope,
  the thermal and mechanical environmental verification, the electrical
  and software validations, and an end-toend on-ground calibration of
  the two-units' flight instrument at the operating wavelengths. The
  instrument has been delivered and installed on the Solar Orbiter
  spacecraft, which is now undergoing all preparatory activities before
  launch.

Title: In-flight performance of the solar UV radiometer LYRA/PROBA-2
Authors: Stockman, Y.; BenMoussa, A.; Dammasch, I.; Defise, J. -M.;
   Dominique, M.; Halain, J. -P.; Hochedez, J. -F.; Koller, S.; Schmutz,
   W.; Schühle, U.
Bibcode: 2017SPIE10565E..0AS
Altcode:
  LYRA is a solar radiometer, part of the PROBA-2 micro-satellite payload
  (Fig. 1). The PROBA-2 [1] mission has been launched on 02 November
  2009 with a Rockot launcher to a Sun-synchronous orbit at an altitude
  of 725 km. Its nominal operation duration is two years with possible
  extension of 2 years. PROBA-2 is a small satellite developed under
  an ESA General Support Technology Program (GSTP) contract to perform
  an in-flight demonstration of new space technologies and support a
  scientific mission for a set of selected instruments [2]. PROBA-2 host
  17 technological demonstrators and 4 scientific instruments. The mission
  is tracked by the ESA Redu Mission Operation Center. One of the four
  scientific instruments is LYRA that monitors the solar irradiance at a
  high cadence (&gt; 20 Hz) in four soft X-Ray to VUV large passbands: the
  "Lyman-Alpha" channel, the "Herzberg" continuum range, the "Aluminium"
  and "Zirconium" filter channels. The radiometric calibration is
  traceable to synchrotron source standards [3]. LYRA benefits from wide
  bandgap detectors based on diamond. It is the first space assessment
  of these revolutionary UV detectors for astrophysics. Diamond sensors
  make the instruments radiation-hard and solar-blind (insensitive to
  the strong solar visible light) and, therefore, visible light blocking
  filters become superfluous. To correlate the data of this new detector
  technology, silicon detectors with well known characteristics are also
  embarked. Due to the strict allocated mass and power budget (5 kg, 5W),
  and poor priority to the payload needs on such platform, an optimization
  and a robustness of the instrument was necessary. The first switch-on
  occured on 16 November 2009. Since then the instrument performances
  have been monitored and analyzed during the commissioning period. This
  paper presents the first-light and preliminary performance analysis.

Title: LYRA, solar uv radiometer on the technology demonstration
    platform PROBA-2
Authors: Stockman, Y.; Hochedez, J. -F.; Schmutz, W.; BenMoussa, A.;
   Defise, J. -M.; Denis, F.; D'Olieslaeger, M.; Dominique, M.; Haenen,
   K.; Halain, J. -P.; Koller, S.; Koizumi, S.; Mortet, V.; Rochus, P.;
   Schühle, U.; Soltani, A.; Theissen, A.
Bibcode: 2017SPIE10567E..3KS
Altcode:
  LYRA is a solar radiometer part of the PROBA 2 micro satellite
  payload. LYRA will monitor the solar irradiance in four soft X-Ray -
  VUV passbands. They have been chosen for their relevance to Solar
  Physics, Aeronomy and SpaceWeather: 1/ Lyman Alpha channel, 2/
  Herzberg continuum range, 3/ Aluminium filter channel (including
  He II at 30.4 nm) and 4/ Zirconium filter channel. The radiometric
  calibration is traceable to synchrotron source standards. The
  stability will be monitored by on-board calibration sources (LEDs),
  which allow us to distinguish between potential degradations of the
  detectors and filters. Additionally, a redundancy strategy maximizes
  the accuracy and the stability of the measurements. LYRA will benefit
  from wide bandgap detectors based on diamond: it will be the first
  space assessment of revolutionary UV detectors. Diamond sensors
  make the instruments radiation-hard and solar-blind (insensitive to
  visible light) and therefore, make dispensable visible light blocking
  filters. To correlate the data of this new detector technology, well
  known technology, such as Si detectors are also embarked. The SWAP
  EUV imaging telescope will operate next to LYRA on PROBA-2. Together,
  they will provide a high performance solar monitor for operational
  space weather nowcasting and research. LYRA demonstrates technologies
  important for future missions such as the ESA Solar Orbiter.

Title: Characterization of the UV detector of Solar Orbiter/Metis
Authors: Uslenghi, Michela; Schühle, Udo H.; Teriaca, Luca; Heerlein,
   Klaus; Werner, Stephan
Bibcode: 2017SPIE10397E..1KU
Altcode:
  Metis, one of the instruments of the ESA mission Solar Orbiter (to be
  launched in February 2019), is a coronograph able to perform broadband
  polarization imaging in the visible range (580-640 nm), and narrow
  band imaging in UV (HI Lyman-α 121.6 nm) . The detector of the UV
  channel is an intensified camera, based on a Star-1000 rad-hard CMOS
  APS coupled via a 2:1 fiber optic taper to a single stage Microchannel
  Plate intensifier, sealed with an entrance MgF<SUB>2</SUB> window
  and provided with an opaque KBr photocathode. Before integration
  in the instrument, the UVDA (UV Detector Assembly) Flight Model
  has been characterized at the MPS laboratory and calibrated in the
  UV range using the detector calibration beamline of the Metrology
  Light Source synchrotron of the Physikalisch-Technische Bundesanstalt
  (PTB). Linearity, spectral calibration, and response uniformity at 121.6
  nm have been measured. Preliminary results are reported in this paper.

Title: The VUV instrument SPICE for Solar Orbiter: performance
    ground testing
Authors: Caldwell, Martin E.; Morris, Nigel; Griffin, Douglas K.;
   Eccleston, Paul; Anderson, Mark; Pastor Santos, Carmen; Bruzzi,
   Davide; Tustain, Samuel; Howe, Chris; Davenne, Jenny; Grundy, Timothy;
   Speight, Roisin; Sidher, Sunil D.; Giunta, Alessandra; Fludra, Andrzej;
   Philippon, Anne; Auchere, Frederic; Hassler, Don; Davila, Joseph M.;
   Thompson, William T.; Schuehle, Udo H.; Meining, Stefan; Walls, Buddy;
   Phelan, P.; Dunn, Greg; Klein, Roman M.; Reichel, Thomas; Gyo, Manfred;
   Munro, Grant J.; Holmes, William; Doyle, Peter
Bibcode: 2017SPIE10397E..08C
Altcode:
  SPICE is an imaging spectrometer operating at vacuum ultraviolet
  (VUV) wavelengths, 70.4 - 79.0 nm and 97.3 - 104.9 nm. It is a
  facility instrument on the Solar Orbiter mission, which carries
  10 science instruments in all, to make observations of the Sun's
  atmosphere and heliosphere, at close proximity to the Sun, i.e to
  0.28 A.U. at perihelion. SPICE's role is to make VUV measurements
  of plasma in the solar atmosphere. SPICE is designed to achieve
  spectral imaging at spectral resolution &gt;1500, spatial resolution
  of several arcsec, and two-dimensional FOV of 11 x16arcmins. The many
  strong constraints on the instrument design imposed by the mission
  requirements prevent the imaging performance from exceeding those of
  previous instruments, but by being closer to the sun there is a gain in
  spatial resolution. The price which is paid is the harsher environment,
  particularly thermal. This leads to some novel features in the design,
  which needed to be proven by ground test programs. These include a
  dichroic solar-transmitting primary mirror to dump the solar heat, a
  high in-flight temperature (60deg.C) and gradients in the optics box,
  and a bespoke variable-line-spacing grating to minimise the number of
  reflective components used. The tests culminate in the systemlevel test
  of VUV imaging performance and pointing stability. We will describe how
  our dedicated facility with heritage from previous solar instruments,
  is used to make these tests, and show the results, firstly on the
  Engineering Model of the optics unit, and more recently on the Flight
  Model. For the keywords, select up to 8 key terms for a search on your
  manuscript's subject.

Title: The qualification campaign of the EUI instrument of Solar
    Orbiter
Authors: Halain, J. -P.; Rochus, P.; Renotte, E.; Hermans, A.; Jacques,
   L.; Mazzoli, A.; Auchère, F.; Berghmans, D.; Harra, L.; Schühle,
   U.; Schmutz, W.; Aznar Cuadrado, R.; Dumesnil, C.; Gyo, M.; Kennedy,
   T.; Verbeeck, C.; Smith, P.
Bibcode: 2016SPIE.9905E..2XH
Altcode:
  The Extreme Ultraviolet Imager (EUI) instrument is one of the ten
  scientific instruments on board the Solar Orbiter mission to be launched
  in October 2018. It will provide full-sun and high-resolution images of
  the solar corona in the extreme ultraviolet (17.1 nm and 30.4 nm) and in
  the vacuum ultraviolet (121.6 nm). The validation of the EUI instrument
  design has been completed with the Assembly, Integration and Test
  (AIT) of the instrument two-units Qualification Model (QM). Optical,
  electrical, electro-magnetic compatibility, thermal and mechanical
  environmental verifications were conducted and are summarized here. The
  integration and test procedures for the Flight Model (FM) instrument
  and sub-systems were also verified. Following the Qualification Review,
  the flight instrument activities were started with the assembly of
  the flight units. The mechanical and thermal acceptance tests and an
  end-to-end final calibration in the (E)UV will then be conducted before
  delivery for integration on the Solar Orbiter Spacecraft by end of 2016.

Title: The SPICE Spectral Imager on Solar Orbiter: Linking the Sun
    to the Heliosphere
Authors: Fludra, Andrzej; Haberreiter, Margit; Peter, Hardi; Vial,
   Jean-Claude; Harrison, Richard; Parenti, Susanna; Innes, Davina;
   Schmutz, Werner; Buchlin, Eric; Chamberlin, Phillip; Thompson,
   William; Gabriel, Alan; Morris, Nigel; Caldwell, Martin; Auchere,
   Frederic; Curdt, Werner; Teriaca, Luca; Hassler, Donald M.; DeForest,
   Craig; Hansteen, Viggo; Carlsson, Mats; Philippon, Anne; Janvier, Miho;
   Wimmer-Schweingruber, Robert; Griffin, Douglas; Davila, Joseph; Giunta,
   Alessandra; Waltham, Nick; Eccleston, Paul; Gottwald, Alexander;
   Klein, Roman; Hanley, John; Walls, Buddy; Howe, Chris; Schuehle, Udo
Bibcode: 2016cosp...41E.607F
Altcode:
  The SPICE (Spectral Imaging of the Coronal Environment) instrument is
  one of the key remote sensing instruments onboard the upcoming Solar
  Orbiter Mission. SPICE has been designed to contribute to the science
  goals of the mission by investigating the source regions of outflows
  and ejection processes which link the solar surface and corona to the
  heliosphere. In particular, SPICE will provide quantitative information
  on the physical state and composition of the solar atmosphere
  plasma. For example, SPICE will access relative abundances of ions to
  study the origin and the spatial/temporal variations of the 'First
  Ionization Potential effect', which are key signatures to trace the
  solar wind and plasma ejections paths within the heliosphere. Here we
  will present the instrument and its performance capability to attain the
  scientific requirements. We will also discuss how different observation
  modes can be chosen to obtain the best science results during the
  different orbits of the mission. To maximize the scientific return of
  the instrument, the SPICE team is working to optimize the instrument
  operations, and to facilitate the data access and their exploitation.

Title: Solar abundances with the SPICE spectral imager on Solar
    Orbiter
Authors: Giunta, Alessandra; Haberreiter, Margit; Peter, Hardi;
   Vial, Jean-Claude; Harrison, Richard; Parenti, Susanna; Innes, Davina;
   Schmutz, Werner; Buchlin, Eric; Chamberlin, Phillip; Thompson, William;
   Bocchialini, Karine; Gabriel, Alan; Morris, Nigel; Caldwell, Martin;
   Auchere, Frederic; Curdt, Werner; Teriaca, Luca; Hassler, Donald M.;
   DeForest, Craig; Hansteen, Viggo; Carlsson, Mats; Philippon, Anne;
   Janvier, Miho; Wimmer-Schweingruber, Robert; Griffin, Douglas; Baudin,
   Frederic; Davila, Joseph; Fludra, Andrzej; Waltham, Nick; Eccleston,
   Paul; Gottwald, Alexander; Klein, Roman; Hanley, John; Walls, Buddy;
   Howe, Chris; Schuehle, Udo; Gyo, Manfred; Pfiffner, Dany
Bibcode: 2016cosp...41E.681G
Altcode:
  Elemental composition of the solar atmosphere and in particular
  abundance bias of low and high First Ionization Potential (FIP)
  elements are a key tracer of the source regions of the solar wind. These
  abundances and their spatio-temporal variations, as well as the other
  plasma parameters , will be derived by the SPICE (Spectral Imaging
  of the Coronal Environment) EUV spectral imager on the upcoming
  Solar Orbiter mission. SPICE is designed to provide spectroheliograms
  (spectral images) using a core set of emission lines arising from ions
  of both low-FIP and high-FIP elements. These lines are formed over
  a wide range of temperatures, enabling the analysis of the different
  layers of the solar atmosphere. SPICE will use these spectroheliograms
  to produce dynamic composition maps of the solar atmosphere to be
  compared to in-situ measurements of the solar wind composition of
  the same elements (i.e. O, Ne, Mg, Fe). This will provide a tool to
  study the connectivity between the spacecraft (the Heliosphere) and
  the Sun. We will discuss the SPICE capabilities for such composition
  measurements.

Title: Hydrogen Ly-α and Ly-β full Sun line profiles observed with
    SUMER/SOHO (1996-2009)
Authors: Lemaire, P.; Vial, J. -C.; Curdt, W.; Schühle, U.;
   Wilhelm, K.
Bibcode: 2015A&A...581A..26L
Altcode:
  Context. Accurate hydrogen spectra emitted by the entire solar disc in
  the Ly-α and Ly-βlines are valuable for deriving the distribution and
  the behaviour of atomic hydrogen in the heliosphere, for understanding
  the UV emissions of solar type stars better, and finally for estimating
  the solar energy input that mainly initiates the chemical processes
  occurring in the planetary and cometary outer atmospheres. <BR /> Aims:
  In this paper we want to accurately determine the irradiance solar
  spectral profiles of Ly-α and Ly-β and their evolution through the
  solar activity cycle 23. <BR /> Methods: The SUMER/SOHO spectrometer is
  a slit spectrometer that is only able to analyse a small part of the
  solar image. Consequently, we used the scattered light properties of
  the telescope to obtain average spectra over the solar disc. Then the
  profile is calibrated using the SOLSTICE/UARS and TIMED/SEE irradiance
  spectra. <BR /> Results: We obtained a set of irradiance Ly-α and
  Ly-β solar spectra with a 0.002 nm resolution through the solar
  activity cycle 23. In each line a relation between the integrated
  profile and the line centre intensity was obtained.Knowing the line
  irradiance, it is possible to deduce the central line profile intensity,
  a critical input into the interplanetary and planetary oxygen and
  hydrogen fluorescent processes. <BR /> Conclusions: The observation
  of H i Ly-α and Ly-β line profiles by SUMER/SOHO during the cycle
  23 allows analysis of the evolution of their characteristics and
  accurate determination of UV radiation input into the solar system. <P
  />Profiles are only available at the CDS via anonymous ftp to <A
  href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr</A>
  (ftp://130.79.128.5) or via <A
  href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/581/A26">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/581/A26</A>

Title: The extreme ultraviolet imager of solar orbiter: optical
    design and alignment scheme
Authors: Halain, J. -P.; Mazzoli, A.; Meining, S.; Rochus, P.; Renotte,
   E.; Auchère, F.; Schühle, U.; Delmotte, F.; Dumesnil, C.; Philippon,
   A.; Mercier, R.; Hermans, A.
Bibcode: 2015SPIE.9604E..0HH
Altcode:
  The Extreme Ultraviolet Imager (EUI) is one of the remote sensing
  instruments on-board the Solar Orbiter mission. It will provide
  dual-band full-Sun images of the solar corona in the extreme ultraviolet
  (17.1 nm and 30.4 nm), and high resolution images of the solar disk in
  both extreme ultraviolet (17.1 nm) and vacuum ultraviolet (Lyman-alpha
  121.6 nm). The EUI optical design takes heritage of previous similar
  instruments. The Full Sun Imager (FSI) channel is a single mirror
  Herschel design telescope. The two High Resolution Imager (HRI)
  channels are based on a two-mirror optical refractive scheme, one
  Ritchey-Chretien and one Gregory optical design for the EUV and the
  Lyman-alpha channels, respectively. The spectral performances of the
  EUI channels are obtained thanks to dedicated mirror multilayer coatings
  and specific band-pass filters. The FSI channel uses a dual-band mirror
  coating combined with aluminum and zirconium band-pass filters. The HRI
  channels use optimized band-pass selection mirror coatings combined
  with aluminum band-pass filters and narrow band interference filters
  for Lyman-alpha. The optical performances result from accurate mirror
  manufacturing tolerances and from a two-step alignment procedure. The
  primary mirrors are first co-aligned. The HRI secondary mirrors
  and focal planes positions are then adjusted to have an optimum
  interferometric cavity in each of these two channels. For that purpose
  a dedicated alignment test setup has been prepared, composed of a dummy
  focal plane assembly representing the detector position. Before the
  alignment on the flight optical bench, the overall alignment method
  has been validated on the Structural and Thermal Model, on a dummy
  bench using flight spare optics, then on the Qualification Model to
  be used for the system verification test and qualifications.

Title: The extreme UV imager telescope on-board the Solar Orbiter
mission: overview of phase C and D
Authors: Halain, J. -P.; Rochus, P.; Renotte, E.; Hermans, A.; Jacques,
   L.; Auchère, F.; Berghmans, D.; Harra, L.; Schühle, U.; Schmutz,
   W.; Zhukov, A.; Aznar Cuadrado, R.; Delmotte, F.; Dumesnil, C.; Gyo,
   M.; Kennedy, T.; Smith, P.; Tandy, J.; Mercier, R.; Verbeeck, C.
Bibcode: 2015SPIE.9604E..0GH
Altcode:
  The Solar Orbiter mission is composed of ten scientific instruments
  dedicated to the observation of the Sun's atmosphere and its
  heliosphere, taking advantage of an out-of ecliptic orbit and at
  perihelion reaching a proximity close to 0.28 A.U. On board Solar
  Orbiter, the Extreme Ultraviolet Imager (EUI) will provide full-Sun
  image sequences of the solar corona in the extreme ultraviolet (17.1
  nm and 30.4 nm), and high-resolution image sequences of the solar disk
  in the extreme ultraviolet (17.1 nm) and in the vacuum ultraviolet
  (121.6 nm). The EUI concept uses heritage from previous similar extreme
  ultraviolet instrument. Additional constraints from the specific orbit
  (thermal and radiation environment, limited telemetry download) however
  required dedicated technologies to achieve the scientific objectives
  of the mission. The development phase C of the instrument and its
  sub-systems has been successfully completed, including thermomechanical
  and electrical design validations with the Structural Thermal Model
  (STM) and the Engineering Model (EM). The instrument STM and EM units
  have been integrated on the respective spacecraft models and will
  undergo the system level tests. In parallel, the Phase D has been
  started with the sub-system qualifications and the flight parts
  manufacturing. The next steps of the EUI development will be the
  instrument Qualification Model (QM) integration and qualification
  tests. The Flight Model (FM) instrument activities will then follow
  with the acceptance tests and calibration campaigns.

Title: VizieR Online Data Catalog: Sun hydrogen Lyman irradiance
    lines profiles (Lemaire+, 2015)
Authors: Lemaire, P.; Vial, J. -C.; Curdt, W.; Schuhle, U.; Wilhelm, K.
Bibcode: 2015yCat..35810026L
Altcode:
  Set of irradiance Ly-α and Ly-β solar spectra with a 0.002nm
  resolution through the solar activity cycle 23. The wavelength distance
  from line center is given every 0.001nm. <P />(2 data files).

Title: Degradation assessment of LYRA after 5 years on orbit -
    Technology Demonstration -
Authors: BenMoussa, A.; Giordanengo, B.; Gissot, S.; Dammasch, I. E.;
   Dominique, M.; Hochedez, J. -F.; Soltani, A.; Bourzgui, N.; Saito,
   T.; Schühle, U.; Gottwald, A.; Kroth, U.; Jones, A. R.
Bibcode: 2015ExA....39...29B
Altcode: 2015ExA...tmp....1B
  We present a long-term assessment of the radiometric calibration and
  degradation of the Large Yield Radiometer (LYRA), which has been on
  orbit since 2009. LYRA is an ultraviolet (UV) solar radiometer and is
  the first space experiment using aboard a pioneering diamond detector
  technology. We show that LYRA has degraded after the commissioning phase
  but is still exploitable scientifically after almost 5 years on orbit
  thanks to its redundancy design and calibration strategy correcting for
  instrument degradation. We focus on the inflight detector's calibration
  and show that diamond photodetectors have not degraded while silicon
  reference photodiodes that are even less exposed to the Sun show an
  increase of their dark current and a decrease of their photoresponse.

Title: The extreme UV imager of solar orbiter: from detailed design
    to flight model
Authors: Halain, J. -P.; Rochus, P.; Renotte, E.; Auchère, F.;
   Berghmans, D.; Harra, L.; Schühle, U.; Schmutz, W.; Zhukov, A.;
   Aznar Cuadrado, R.; Delmotte, F.; Dumesnil, C.; Gyo, M.; Kennedy,
   T.; Mercier, R.; Verbeeck, F.; Thome, M.; Heerlein, K.; Hermans, A.;
   Jacques, L.; Mazzoli, A.; Meining, S.; Rossi, L.; Tandy, J.; Smith,
   P.; Winter, B.
Bibcode: 2014SPIE.9144E..08H
Altcode:
  The Extreme Ultraviolet Imager (EUI) on-board the Solar Orbiter mission
  will provide full-sun and high-resolution image sequences of the solar
  atmosphere at selected spectral emission lines in the extreme and vacuum
  ultraviolet. After the breadboarding and prototyping activities that
  focused on key technologies, the EUI project has completed the design
  phase and has started the final manufacturing of the instrument and its
  validation. The EUI instrument has successfully passed its Critical
  Design Review (CDR). The process validated the detailed design of
  the Optical Bench unit and of its sub-units (entrance baffles, doors,
  mirrors, camera, and filter wheel mechanisms), and of the Electronic
  Box unit. In the same timeframe, the Structural and Thermal Model
  (STM) test campaign of the two units have been achieved, and allowed
  to correlate the associated mathematical models. The lessons learned
  from STM and the detailed design served as input to release the
  manufacturing of the Qualification Model (QM) and of the Flight Model
  (FM). The QM will serve to qualify the instrument units and sub-units,
  in advance of the FM acceptance tests and final on-ground calibration.

Title: Scattered Lyman-α radiation of comet 2012/S1 (ISON) observed
    by SUMER/SOHO
Authors: Curdt, W.; Boehnhardt, H.; Vincent, J. -B.; Solanki, S. K.;
   Schühle, U.; Teriaca, L.
Bibcode: 2014A&A...567L...1C
Altcode: 2014arXiv1406.4343C
  During its sungrazing perihelion passage, comet ISON appeared in
  the field of view of the SUMER spectrometer and allowed unique
  observations at far-ultraviolet wavelengths with high spatial and
  temporal resolution. We report results of these observations completed
  on November 28, 2013, when the comet was only 2.82 R<SUB>ʘ</SUB>
  away from the Sun. Our data show the arrow-shaped dust tail in Ly-α
  emission trailing behind the predicted position of the nucleus, but
  offset from the trajectory. We interpret the emission as sunlight
  that is scattered at μm-sized dust particles. We modeled the dust
  emission and dynamics to reproduce the appearance of the tail. We
  were unable to detect any signature of cometary gas or plasma around
  the expected position of the nucleus and conclude that the outgassing
  processes must have stopped before the observation started. Moreover,
  the model we used to reproduce the observed dust tail needs a sharp
  fall-off of the dust production hours before perihelion transit. We
  compare the radiances of the disk and the dust tail for an estimate
  of the dust column density and tail mass.

Title: Scattered Lyman-alpha radiation of comet 2012/S1 (ISON)
    observed by SUMER/SOHO
Authors: Curdt, W.; Boehnhardt, H.; Germerott, D.; Schuehle, U.;
   Solanki, S.; Teriaca, L.; Vincent, J.
Bibcode: 2014acm..conf..119C
Altcode:
  During its recent perihelion passage, comet ISON came so close to
  the Sun that it appeared in the field of view (FOV) of the SUMER
  spectrometer on SOHO and allowed unique observations at far-UV
  wavelengths with high spatial and temporal resolution. We report results
  of these observations completed during the comet's encounter with the
  Sun on November 28.75, 2013. Our data show the dust tail trailing behind
  the predicted position of the nucleus seen in Lyman-alpha emission
  as light from the solar disk that is scattered by micron-sized dust
  particles. The arrow-shaped tail is offset from the trajectory and not
  aligned with it. We model the dust emission and dynamics to reproduce
  the appearance of the tail. We could not detect any signature of
  cometary gas or plasma around the expected position of the nucleus
  and conclude that the out-gassing processes must have stopped before
  the comet entered our FOV. Also the model we used to reproduce the
  observed dust tail needs a sharp fall-off of the dust production hours
  before perihelion. We compare the radiance of the dust tail to the
  Lyman-alpha emission of the disk for an estimate of the dust column
  density. After observing 18 years mostly solar targets, this was the
  first time that SUMER completed spectroscopic observations of a comet.

Title: The SUMER Data in the SOHO Archive
Authors: Curdt, W.; Germerott, D.; Wilhelm, K.; Schühle, U.; Teriaca,
   L.; Innes, D.; Bocchialini, K.; Lemaire, P.
Bibcode: 2014SoPh..289.2345C
Altcode: 2013arXiv1309.1314C
  We have released an archive of all observational data of the VUV
  spectrometer Solar Ultraviolet Measurements of Emitted Radiation
  (SUMER) on SOHO that have been acquired until now. The operational
  phase started with `first light' observations on 27 January 1996 and
  will end in 2014. Future data will be added to the archive when they
  become available. The archive consists of a set of raw data (Level
  0) and a set of data that are processed and calibrated to the best
  knowledge we have today (Level 1). This communication describes step
  by step the data acquisition and processing that has been applied in an
  automated manner to build the archive. It summarizes the expertise and
  insights into the scientific use of SUMER spectra that has accumulated
  over the years. It also indicates possibilities for further enhancement
  of the data quality. With this article we intend to convey our own
  understanding of the instrument performance to the scientific community
  and to introduce the new, standard FITS-format database.

Title: On-Orbit Degradation of Solar Instruments
Authors: BenMoussa, A.; Gissot, S.; Schühle, U.; Del Zanna, G.;
   Auchère, F.; Mekaoui, S.; Jones, A. R.; Walton, D.; Eyles, C. J.;
   Thuillier, G.; Seaton, D.; Dammasch, I. E.; Cessateur, G.; Meftah,
   M.; Andretta, V.; Berghmans, D.; Bewsher, D.; Bolsée, D.; Bradley,
   L.; Brown, D. S.; Chamberlin, P. C.; Dewitte, S.; Didkovsky, L. V.;
   Dominique, M.; Eparvier, F. G.; Foujols, T.; Gillotay, D.; Giordanengo,
   B.; Halain, J. P.; Hock, R. A.; Irbah, A.; Jeppesen, C.; Judge,
   D. L.; Kretzschmar, M.; McMullin, D. R.; Nicula, B.; Schmutz, W.;
   Ucker, G.; Wieman, S.; Woodraska, D.; Woods, T. N.
Bibcode: 2013SoPh..288..389B
Altcode: 2013arXiv1304.5488B
  We present the lessons learned about the degradation observed in
  several space solar missions, based on contributions at the Workshop
  about On-Orbit Degradation of Solar and Space Weather Instruments
  that took place at the Solar Terrestrial Centre of Excellence (Royal
  Observatory of Belgium) in Brussels on 3 May 2012. The aim of this
  workshop was to open discussions related to the degradation observed
  in Sun-observing instruments exposed to the effects of the space
  environment. This article summarizes the various lessons learned
  and offers recommendations to reduce or correct expected degradation
  with the goal of increasing the useful lifespan of future and ongoing
  space missions.

Title: The SWAP EUV Imaging Telescope Part I: Instrument Overview
    and Pre-Flight Testing
Authors: Seaton, D. B.; Berghmans, D.; Nicula, B.; Halain, J. -P.; De
   Groof, A.; Thibert, T.; Bloomfield, D. S.; Raftery, C. L.; Gallagher,
   P. T.; Auchère, F.; Defise, J. -M.; D'Huys, E.; Lecat, J. -H.; Mazy,
   E.; Rochus, P.; Rossi, L.; Schühle, U.; Slemzin, V.; Yalim, M. S.;
   Zender, J.
Bibcode: 2013SoPh..286...43S
Altcode: 2012SoPh..tmp..217S; 2012arXiv1208.4631S
  The Sun Watcher with Active Pixels and Image Processing (SWAP) is
  an EUV solar telescope onboard ESA's Project for Onboard Autonomy 2
  (PROBA2) mission launched on 2 November 2009. SWAP has a spectral
  bandpass centered on 17.4 nm and provides images of the low solar
  corona over a 54×54 arcmin field-of-view with 3.2 arcsec pixels and
  an imaging cadence of about two minutes. SWAP is designed to monitor
  all space-weather-relevant events and features in the low solar
  corona. Given the limited resources of the PROBA2 microsatellite,
  the SWAP telescope is designed with various innovative technologies,
  including an off-axis optical design and a CMOS-APS detector. This
  article provides reference documentation for users of the SWAP image
  data.

Title: Status of RAISE, the Rapid Acquisition Imaging Spectrograph
    Experiment
Authors: Laurent, Glenn T.; Hassler, D. M.; DeForest, C.; Ayres,
   T. R.; Davis, M.; De Pontieu, B.; Schuehle, U.; Warren, H.
Bibcode: 2013SPD....44..145L
Altcode:
  The Rapid Acquisition Imaging Spectrograph Experiment (RAISE) sounding
  rocket payload is a high speed scanning-slit imaging spectrograph
  designed to observe the dynamics and heating of the solar chromosphere
  and corona on time scales as short as 100 ms, with 1 arcsec spatial
  resolution and a velocity sensitivity of 1-2 km/s. The instrument is
  based on a new class of UV/EUV imaging spectrometers that use only
  two reflections to provide quasi-stigmatic performance simultaneously
  over multiple wavelengths and spatial fields. The design uses an
  off-axis parabolic telescope mirror to form a real image of the sun
  on the spectrometer entrance aperture. A slit then selects a portion
  of the solar image, passing its light onto a near-normal incidence
  toroidal grating, which re-images the spectrally dispersed radiation
  onto two array detectors. Two full spectral passbands over the same
  one-dimensional spatial field are recorded simultaneously with no
  scanning of the detectors or grating. The two different spectral
  bands (1st-order 1205-1243Å and 1526-1564Å) are imaged onto two
  intensified Active Pixel Sensor (APS) detectors whose focal planes are
  individually adjusted for optimized performance. The telescope and
  grating are coated with B4C to enhance short wavelength (2nd order)
  reflectance, enabling the instrument to record the brightest lines
  between 602-622Å and 761-780Å at the same time. RAISE reads out the
  full field of both detectors at 5-10 Hz, allowing us to record over
  1,500 complete spectral observations in a single 5-minute rocket flight,
  opening up a new domain of high time resolution spectral imaging and
  spectroscopy. We present an overview of the project, a summary of the
  maiden flight results, and an update on instrument status.Abstract
  (2,250 Maximum Characters): The Rapid Acquisition Imaging Spectrograph
  Experiment (RAISE) sounding rocket payload is a high speed scanning-slit
  imaging spectrograph designed to observe the dynamics and heating of the
  solar chromosphere and corona on time scales as short as 100 ms, with 1
  arcsec spatial resolution and a velocity sensitivity of 1-2 km/s. The
  instrument is based on a new class of UV/EUV imaging spectrometers
  that use only two reflections to provide quasi-stigmatic performance
  simultaneously over multiple wavelengths and spatial fields. The design
  uses an off-axis parabolic telescope mirror to form a real image of
  the sun on the spectrometer entrance aperture. A slit then selects
  a portion of the solar image, passing its light onto a near-normal
  incidence toroidal grating, which re-images the spectrally dispersed
  radiation onto two array detectors. Two full spectral passbands over
  the same one-dimensional spatial field are recorded simultaneously with
  no scanning of the detectors or grating. The two different spectral
  bands (1st-order 1205-1243Å and 1526-1564Å) are imaged onto two
  intensified Active Pixel Sensor (APS) detectors whose focal planes are
  individually adjusted for optimized performance. The telescope and
  grating are coated with B4C to enhance short wavelength (2nd order)
  reflectance, enabling the instrument to record the brightest lines
  between 602-622Å and 761-780Å at the same time. RAISE reads out the
  full field of both detectors at 5-10 Hz, allowing us to record over
  1,500 complete spectral observations in a single 5-minute rocket flight,
  opening up a new domain of high time resolution spectral imaging and
  spectroscopy. We present an overview of the project, a summary of the
  maiden flight results, and an update on instrument status.

Title: LEMUR: Large European module for solar Ultraviolet
    Research. European contribution to JAXA's Solar-C mission
Authors: Teriaca, Luca; Andretta, Vincenzo; Auchère, Frédéric;
   Brown, Charles M.; Buchlin, Eric; Cauzzi, Gianna; Culhane, J. Len;
   Curdt, Werner; Davila, Joseph M.; Del Zanna, Giulio; Doschek, George
   A.; Fineschi, Silvano; Fludra, Andrzej; Gallagher, Peter T.; Green,
   Lucie; Harra, Louise K.; Imada, Shinsuke; Innes, Davina; Kliem,
   Bernhard; Korendyke, Clarence; Mariska, John T.; Martínez-Pillet,
   Valentin; Parenti, Susanna; Patsourakos, Spiros; Peter, Hardi; Poletto,
   Luca; Rutten, Robert J.; Schühle, Udo; Siemer, Martin; Shimizu,
   Toshifumi; Socas-Navarro, Hector; Solanki, Sami K.; Spadaro, Daniele;
   Trujillo-Bueno, Javier; Tsuneta, Saku; Dominguez, Santiago Vargas;
   Vial, Jean-Claude; Walsh, Robert; Warren, Harry P.; Wiegelmann,
   Thomas; Winter, Berend; Young, Peter
Bibcode: 2012ExA....34..273T
Altcode: 2011ExA...tmp..135T; 2011arXiv1109.4301T
  The solar outer atmosphere is an extremely dynamic environment
  characterized by the continuous interplay between the plasma and the
  magnetic field that generates and permeates it. Such interactions play a
  fundamental role in hugely diverse astrophysical systems, but occur at
  scales that cannot be studied outside the solar system. Understanding
  this complex system requires concerted, simultaneous solar observations
  from the visible to the vacuum ultraviolet (VUV) and soft X-rays, at
  high spatial resolution (between 0.1'' and 0.3''), at high temporal
  resolution (on the order of 10 s, i.e., the time scale of chromospheric
  dynamics), with a wide temperature coverage (0.01 MK to 20 MK,
  from the chromosphere to the flaring corona), and the capability of
  measuring magnetic fields through spectropolarimetry at visible and
  near-infrared wavelengths. Simultaneous spectroscopic measurements
  sampling the entire temperature range are particularly important. These
  requirements are fulfilled by the Japanese Solar-C mission (Plan B),
  composed of a spacecraft in a geosynchronous orbit with a payload
  providing a significant improvement of imaging and spectropolarimetric
  capabilities in the UV, visible, and near-infrared with respect to
  what is available today and foreseen in the near future. The Large
  European Module for solar Ultraviolet Research (LEMUR), described
  in this paper, is a large VUV telescope feeding a scientific payload
  of high-resolution imaging spectrographs and cameras. LEMUR consists
  of two major components: a VUV solar telescope with a 30 cm diameter
  mirror and a focal length of 3.6 m, and a focal-plane package composed
  of VUV spectrometers covering six carefully chosen wavelength ranges
  between 170 Å and 1270 Å. The LEMUR slit covers 280'' on the Sun with
  0.14'' per pixel sampling. In addition, LEMUR is capable of measuring
  mass flows velocities (line shifts) down to 2 km s<SUP> - 1</SUP> or
  better. LEMUR has been proposed to ESA as the European contribution
  to the Solar C mission.

Title: Multi Element Telescope for Imaging and Spectroscopy (METIS)
    coronagraph for the Solar Orbiter mission
Authors: Antonucci, Ester; Fineschi, Silvano; Naletto, Giampiero;
   Romoli, Marco; Spadaro, Daniele; Nicolini, Gianalfredo; Nicolosi,
   Piergiorgio; Abbo, Lucia; Andretta, Vincenzo; Bemporad, Alessandro;
   Auchère, Frédéric; Berlicki, Arkadiusz; Bruno, Roberto; Capobianco,
   Gerardo; Ciaravella, Angela; Crescenzio, Giuseppe; Da Deppo, Vania;
   D'Amicis, Raffaella; Focardi, Mauro; Frassetto, Fabio; Heinzel,
   Peter; Lamy, Philippe L.; Landini, Federico; Massone, Giuseppe;
   Malvezzi, Marco A.; Moses, J. Dan; Pancrazzi, Maurizio; Pelizzo,
   Maria-Guglielmina; Poletto, Luca; Schühle, Udo H.; Solanki, Sami K.;
   Telloni, Daniele; Teriaca, Luca; Uslenghi, Michela
Bibcode: 2012SPIE.8443E..09A
Altcode:
  METIS, the “Multi Element Telescope for Imaging and Spectroscopy”,
  is a coronagraph selected by the European Space Agency to be part of
  the payload of the Solar Orbiter mission to be launched in 2017. The
  unique profile of this mission will allow 1) a close approach to the
  Sun (up to 0.28 A.U.) thus leading to a significant improvement in
  spatial resolution; 2) quasi co-rotation with the Sun, resulting in
  observations that nearly freeze for several days the large-scale outer
  corona in the plane of the sky and 3) unprecedented out-of-ecliptic
  view of the solar corona. This paper describes the experiment concept
  and the observational tools required to achieve the science drivers
  of METIS. METIS will be capable of obtaining for the first time: •
  simultaneous imaging of the full corona in polarized visible-light
  (590-650 nm) and narrow-band ultraviolet HI Lyman α (121.6 nm); •
  monochromatic imaging of the full corona in the extreme ultraviolet
  He II Lyman α (30.4 nm); • spectrographic observations of the HI
  and He II Ly α in corona. These measurements will allow a complete
  characterization of the three most important plasma components of
  the corona and the solar wind, that is, electrons, hydrogen, and
  helium. This presentation gives an overview of the METIS imaging and
  spectroscopic observational capabilities to carry out such measurements.

Title: A prototype of the UV detector for METIS on Solar Orbiter
Authors: Uslenghi, M.; Incorvaia, S.; Fiorini, M.; Schühle, U. H.;
   Teriaca, L.; Wilkinson, E.; Siegmund, O. H.; Antonucci, E.; Fineschi,
   S.; Naletto, G.; Nicolini, G.; Nicolosi, G.; Romoli, M.; Focardi, M.
Bibcode: 2012SPIE.8443E..3IU
Altcode:
  METIS (Multi Element Telescope for Imaging and Spectroscopy) is one of
  the instruments included in the science payload of the ESA mission Solar
  Orbiter: a coronograph able to perform broadband polarization imaging
  in the visible range, and narrow band imaging in UV (HI Lyman-α)
  and EUV (HeII Lyman-α). In addition, it will acquire spectra of the
  solar corona simultaneously to UV/EUV imaging. It will be equipped
  with two detectors: a hybrid APS dedicated to the visible channel and
  an Intensified APS for the UV/EUV channel. The spectroscopic channel
  will share the same detector as the UV/EUV corona imaging, with the
  spectrum imaged on a portion of the detector not used by the corona
  image. We present the development of the UV/EUV detector consisting
  of a CMOS APS imaging device to be coupled with a microchannel plate
  intensifier. Other than constraints related to the harsh environment
  (radiation, temperature, visible stray-light), the METIS UV detector has
  the additional challenge of managing different count rates associated
  with the three different kind of measurements (UV imaging, EUV imaging
  and spectroscopy). The required dynamic range is further extended
  since observations will be planned at different distances from the
  Sun, varying image scale over a fixed vignetting function. We will
  present the architecture of this UV detector, describing the prototype
  developed in order to optimize the performance on the overall dynamic
  range required by METIS.

Title: METIS: a novel coronagraph design for the Solar Orbiter mission
Authors: Fineschi, Silvano; Antonucci, Ester; Naletto, Giampiero;
   Romoli, Marco; Spadaro, Daniele; Nicolini, Gianalfredo; Abbo, Lucia;
   Andretta, Vincenzo; Bemporad, Alessandro; Berlicki, Arkadiusz;
   Capobianco, Gerardo; Crescenzio, Giuseppe; Da Deppo, Vania; Focardi,
   Mauro; Landini, Federico; Massone, Giuseppe; Malvezzi, Marco A.;
   Moses, J. Dan; Nicolosi, Piergiorgio; Pancrazzi, Maurizio; Pelizzo,
   Maria-Guglielmina; Poletto, Luca; Schühle, Udo H.; Solanki, Sami K.;
   Telloni, Daniele; Teriaca, Luca; Uslenghi, Michela
Bibcode: 2012SPIE.8443E..3HF
Altcode:
  METIS (Multi Element Telescope for Imaging and Spectroscopy) METIS,
  the “Multi Element Telescope for Imaging and Spectroscopy”,
  is a coronagraph selected by the European Space Agency to be part
  of the payload of the Solar Orbiter mission to be launched in
  2017. The mission profile will bring the Solar Orbiter spacecraft
  as close to the Sun as 0.3 A.U., and up to 35° out-of-ecliptic
  providing a unique platform for helio-synchronous observations of
  the Sun and its polar regions. METIS coronagraph is designed for
  multi-wavelength imaging and spectroscopy of the solar corona. This
  presentation gives an overview of the innovative design elements of
  the METIS coronagraph. These elements include: i) multi-wavelength,
  reflecting Gregorian-telescope; ii) multilayer coating optimized for
  the extreme UV (30.4 nm, HeII Lyman-α) with a reflecting cap-layer
  for the UV (121.6 nm, HI Lyman-α) and visible-light (590-650); iii)
  inverse external-occulter scheme for reduced thermal load at spacecraft
  peri-helion; iv) EUV/UV spectrograph using the telescope primary mirror
  to feed a 1<SUP>st</SUP> and 4<SUP>th</SUP>-order spherical varied
  line-spaced (SVLS) grating placed on a section of the secondary mirror;
  v) liquid crystals electro-optic polarimeter for observations of the
  visible-light K-corona. The expected performances are also presented.

Title: The EUI instrument on board the Solar Orbiter mission: from
    breadboard and prototypes to instrument model validation
Authors: Halain, J. -P.; Rochus, P.; Renotte, E.; Appourchaux, T.;
   Berghmans, D.; Harra, L.; Schühle, U.; Schmutz, W.; Auchère, F.;
   Zhukov, A.; Dumesnil, C.; Delmotte, F.; Kennedy, T.; Mercier, R.;
   Pfiffner, D.; Rossi, L.; Tandy, J.; BenMoussa, A.; Smith, P.
Bibcode: 2012SPIE.8443E..07H
Altcode:
  The Solar Orbiter mission will explore the connection between the Sun
  and its heliosphere, taking advantage of an orbit approaching the Sun at
  0.28 AU. As part of this mission, the Extreme Ultraviolet Imager (EUI)
  will provide full-sun and high-resolution image sequences of the solar
  atmosphere at selected spectral emission lines in the extreme and vacuum
  ultraviolet. To achieve the required scientific performances under the
  challenging constraints of the Solar Orbiter mission it was required
  to further develop existing technologies. As part of this development,
  and of its maturation of technology readiness, a set of breadboard and
  prototypes of critical subsystems have thus been realized to improve
  the overall instrument design. The EUI instrument architecture, its
  major components and sub-systems are described with their driving
  constraints and the expected performances based on the breadboard and
  prototype results. The instrument verification and qualification plan
  will also be discussed. We present the thermal and mechanical model
  validation, the instrument test campaign with the structural-thermal
  model (STM), followed by the other instrument models in advance of
  the flight instrument manufacturing and AIT campaign.

Title: CMOS sensor and camera for the PHI instrument on board Solar
Orbiter: evaluation of the radiation tolerance
Authors: Piqueras, J.; Heerlein, K.; Werner, S.; Enge, R.; Schühle,
   U.; Woch, J.; De Ridder, T.; Meynants, G.; Wolfs, B.; Lepage, G.;
   Diels, W.
Bibcode: 2012SPIE.8453E..14P
Altcode:
  The ESA/NASA Solar Orbiter mission, to be launched in 2017, will
  explore the Sun at a much closer distance than any previous solar
  observatory. On board the spacecraft, a high-resolution magnetograph
  (PHI) will provide two-dimensional measurements of the photospheric
  vector magnetic field and line-of-sight velocity. The environmental
  conditions encountered during the mission, together with the
  stringent performance requirements of the instrument, define the
  set of specifications for the camera system. A custom designed
  CMOS sensor (with 2048×2050 pixels) has been developed to fulfill
  the aimed radiation hardness and performance. This sensor must
  demonstrate a cadence above 10 fps with a full-well capacity higher
  than 10<SUP>5</SUP> electrons in a 10-μm pixel pitch. We report the
  characterization and qualification tests. The radiation test campaign
  has been completed up to a TID of 150 krad(Si), proton fluence up to
  4 × 10<SUP>11</SUP> at 10 MeV and 2 × 10<SUP>11</SUP> at 20 MeV, and
  with heavy ions to check for latch-up and SEFI failures. In parallel,
  a radiation tolerant camera electronic readout system has been built
  to control the sensor and readout images, digitize the data, and
  communicate with the data handling system of the PHI instrument. In
  addition, we present the main issues related to the camera design and
  future perspectives.

Title: The solar hydrogen Lyman α to Lyman β line ratio
Authors: Lemaire, P.; Vial, J. -C.; Curdt, W.; Schühle, U.; Woods,
   T. N.
Bibcode: 2012A&A...542L..25L
Altcode:
  <BR /> Aims: We investigate the variation in the solar hydrogen Lyman
  α (Lyα) to Lyman β (Lyβ) line ratio as a function of the solar
  activity by taking into account new results obtained by SoHO/SUMER
  and TIMED/SEE. <BR /> Methods: We reanalyze data of quiet and active
  regions previously collected with the LPSP multichannel instrument on
  OSO8. We then re-examine data obtained on the solar disk with SUMER
  and compare them with previous data. In a second step, we use the
  full Sun H i Lyβ profiles to determine the Lyβ contribution to the
  SEE profiles obtained with a 0.4 nm full width at half-maximum. The
  variation in the Lyα to Lyβ line ratio is then measured for part
  of the solar cycle 23 (2002-2008). <BR /> Results: We determine the
  radiance line ratio of the solar H i Lyα to Lyβ line for a quiet Sun
  area and the relation between the ratio of the Lyα to Lyβ irradiance
  and the Lyα solar irradiance.

Title: Solar magnetism eXplorer (SolmeX). Exploring the magnetic
    field in the upper atmosphere of our closest star
Authors: Peter, Hardi; Abbo, L.; Andretta, V.; Auchère, F.; Bemporad,
   A.; Berrilli, F.; Bommier, V.; Braukhane, A.; Casini, R.; Curdt,
   W.; Davila, J.; Dittus, H.; Fineschi, S.; Fludra, A.; Gandorfer, A.;
   Griffin, D.; Inhester, B.; Lagg, A.; Landi Degl'Innocenti, E.; Maiwald,
   V.; Sainz, R. Manso; Martínez Pillet, V; Matthews, S.; Moses, D.;
   Parenti, S.; Pietarila, A.; Quantius, D.; Raouafi, N. -E.; Raymond, J.;
   Rochus, P.; Romberg, O.; Schlotterer, M.; Schühle, U.; Solanki, S.;
   Spadaro, D.; Teriaca, L.; Tomczyk, S.; Trujillo Bueno, J.; Vial, J. -C.
Bibcode: 2012ExA....33..271P
Altcode: 2011arXiv1108.5304P; 2011ExA...tmp..134P
  The magnetic field plays a pivotal role in many fields of
  Astrophysics. This is especially true for the physics of the solar
  atmosphere. Measuring the magnetic field in the upper solar atmosphere
  is crucial to understand the nature of the underlying physical
  processes that drive the violent dynamics of the solar corona—that
  can also affect life on Earth. SolmeX, a fully equipped solar space
  observatory for remote-sensing observations, will provide the first
  comprehensive measurements of the strength and direction of the
  magnetic field in the upper solar atmosphere. The mission consists
  of two spacecraft, one carrying the instruments, and another one in
  formation flight at a distance of about 200 m carrying the occulter to
  provide an artificial total solar eclipse. This will ensure high-quality
  coronagraphic observations above the solar limb. SolmeX integrates two
  spectro-polarimetric coronagraphs for off-limb observations, one in
  the EUV and one in the IR, and three instruments for observations on
  the disk. The latter comprises one imaging polarimeter in the EUV for
  coronal studies, a spectro-polarimeter in the EUV to investigate the low
  corona, and an imaging spectro-polarimeter in the UV for chromospheric
  studies. SOHO and other existing missions have investigated the emission
  of the upper atmosphere in detail (not considering polarization),
  and as this will be the case also for missions planned for the near
  future. Therefore it is timely that SolmeX provides the final piece of
  the observational quest by measuring the magnetic field in the upper
  atmosphere through polarimetric observations.

Title: LEMUR (Large European Module for solar Ultraviolet Research):
    a VUV imaging spectrograph for the JAXA Solar-C Mission
Authors: Korendyke, Clarence M.; Teriaca, Luca; Doschek, George A.;
   Harra, Louise K.; Schühle, Udo H.; Shimizu, Toshifumi
Bibcode: 2011SPIE.8148E..0IK
Altcode: 2011SPIE.8148E..17K
  LEMUR is a VUV imaging spectrograph with 0.28" resolution. Incident
  solar radiation is imaged onto the spectrograph slit by a single
  mirror telescope consisting of a 30-cm steerable f/12 off-axis
  paraboloid mirror. The spectrograph slit is imaged and dispersed by
  a highly corrected grating that focuses the solar spectrum over the
  detectors. The mirror is coated with a suitable multilayer with B4C
  top-coating providing a reflectance peak around 18.5 nm besides the
  usual B4C range above 500Å. The grating is formed by two halves, one
  optimized for performances around 185Å and the other above 500Å. Three
  intensified CCD cameras will record spectra above 50 nm while a large
  format CCD array with an aluminum filter will be used around 185Å.

Title: The Lyman-alpha telescope of the extreme ultraviolet imager
    on Solar Orbiter
Authors: Schühle, Udo; Halain, Jean-Philippe; Meining, Stefan;
   Teriaca, Luca
Bibcode: 2011SPIE.8148E..0KS
Altcode: 2011SPIE.8148E..19S
  On the Solar Orbiter mission, the Extreme Ultraviolet Imager (EUI)
  set of filtergraph-telescopes consists of two highresolution imagers
  (HRI) and one dual-band full Sun imager (FSI) that will provide images
  of the solar atmosphere in the extreme ultraviolet and in the Lyman-α
  line of hydrogen at 121.6 nm. The Lyman-α HRI, in particular, will
  provide imaging of the upper chromospheres/lower transition region of
  the Sun at unprecedented high cadence and at an angular resolution of 1"
  (corresponding to a spatial resolution of 200 km at perihelion). For
  vacuum-ultraviolet imaging of the Sun the main requirements for the
  instrumentation are high resolution, high cadence, and large dynamic
  range. We present here the novel solutions of the instrument design
  and show in detail the predicted performance of this telescope. We
  describe in detail how the high throughput and spectral purity at 121.6
  nm is achieved. The technical solutions include multilayer coatings
  of the telescope mirrors for high reflectance at 121.6 nm, combined
  with interference filters and a multichannel-plate intensified CMOS
  active pixel camera. We make use of the design flexibilities of this
  camera to optimize the dynamic range in the focal plane.

Title: The technical challenges of the Solar-Orbiter EUI instrument
Authors: Halain, Jean-Philippe; Rochus, Pierre; Appourchaux, Thierry;
   Berghmans, David; Harra, Louise; Schühle, Udo; Auchère, Frédéric;
   Zhukov, Andrei; Renotte, Etienne; Defise, Jean-Marc; Rossi, Laurence;
   Fleury-Frenette, Karl; Jacques, Lionel; Hochedez, Jean-François;
   Ben Moussa, Ali
Bibcode: 2010SPIE.7732E..0RH
Altcode: 2010SPIE.7732E..20H
  The Extreme Ultraviolet Imager (EUI) onboard Solar Orbiter consists of
  a suite of two high-resolution imagers (HRI) and one dual-band full
  Sun imager (FSI) that will provide EUV and Lyman-α images of the
  solar atmospheric layers above the photosphere. The EUI instrument is
  based on a set of challenging new technologies allowing to reach the
  scientific objectives and to cope with the hard space environment of
  the Solar Orbiter mission. The mechanical concept of the EUI instrument
  is based on a common structure supporting the HRI and FSI channels,
  and a separated electronic box. A heat rejection baffle system is
  used to reduce the Sun heat load and provide a first protection level
  against the solar disk straylight. The spectral bands are selected by
  thin filters and multilayer mirror coatings. The detectors are 10μm
  pitch back illuminated CMOS Active Pixel Sensors (APS), best suited
  for the EUI science requirements and radiation hardness. This paper
  presents the EUI instrument concept and its major sub-systems. The
  current developments of the instrument technologies are also summarized.

Title: First light of SWAP on-board PROBA2
Authors: Halain, Jean-Philippe; Berghmans, David; Defise, Jean-Marc;
   Renotte, Etienne; Thibert, Tanguy; Mazy, Emmanuel; Rochus, Pierre;
   Nicula, Bogdan; de Groof, Anik; Seaton, Dan; Schühle, Udo
Bibcode: 2010SPIE.7732E..0PH
Altcode: 2010SPIE.7732E..18H
  The SWAP telescope (Sun Watcher using Active Pixel System detector
  and Image Processing) is an instrument launched on 2nd November 2009
  on-board the ESA PROBA2 technological mission. SWAP is a space weather
  sentinel from a low Earth orbit, providing images at 174 nm of the
  solar corona. The instrument concept has been adapted to the PROBA2
  mini-satellite requirements (compactness, low power electronics and
  a-thermal opto-mechanical system). It also takes advantage of the
  platform pointing agility, on-board processor, Packetwire interface
  and autonomous operations. The key component of SWAP is a radiation
  resistant CMOS-APS detector combined with onboard compression and
  data prioritization. SWAP has been developed and qualified at the
  Centre Spatial de LiÃ¨ge (CSL) and calibrated at the PTBBessy
  facility. After launch, SWAP has provided its first images on 14th
  November 2009 and started its nominal, scientific phase in February
  2010, after 3 months of platform and payload commissioning. This
  paper summarizes the latest SWAP developments and qualifications,
  and presents the first light results.

Title: The SUMER Ly-α line profile in quiescent prominences
Authors: Curdt, W.; Tian, H.; Teriaca, L.; Schühle, U.
Bibcode: 2010A&A...511L...4C
Altcode: 2010arXiv1002.1197C
  <BR /> Aims: As the result of a novel observing technique, we publish
  for the first time SoHO-SUMER observations of the true spectral line
  profile of hydrogen Lyman-α in quiescent prominences. Because SoHO is
  not in Earth orbit, our high-quality data set is free of geocoronal
  absorption. We studied the line profile to complement earlier
  observations of the higher Lyman lines and to substantiate recent
  model predictions. <BR /> Methods: We applied the reduced-aperture
  observing mode to two prominence targets and did a statistical
  analysis of the line profiles in both data sets. In particular, we
  investigated the shape of the profile, the radiance distribution, and
  the line shape-to-radiance interrelation. We also compared Ly-α data
  to co-temporal λ 1206 Si iii data. <BR /> Results: We find that the
  average profile of Ly-α has a blue-peak dominance and is reversed
  more if the line-of-sight is perpendicular to the field lines. The
  contrast of Ly-α prominence emission rasters is very low, and the
  radiance distribution differs from the log-normal distribution of the
  disk. Features in the Si iii line are not always co-spatial with Ly-α
  emission. <BR /> Conclusions: Our empirical results support recent
  multi-thread models, which predict that asymmetries and depths of the
  self-reversal depend on the orientation of the prominence axis relative
  to the line-of-sight.

Title: Solar-blind UV detectors based on wide band gap semiconductors
Authors: Schuhle, Udo; Hochedez, Jean-Francois
Bibcode: 2010ISSIR...9..429S
Altcode:
  Solid-state photon detectors based on semiconductors other than
  silicon are not yet considered mature technology but their current
  development opens new possibilities, also for space observations. Such
  devices are especially attractive for ultraviolet radiation detection,
  as semiconductor materials with band gaps larger than that of silicon
  can be produced and used as "visible-blind" or "solar-blind" detectors
  that are not affected by daylight. Here we evaluate the advantages
  of such detectors compared to silicon-based devices and report on the
  semiconductor detectors that have been fabricated in recent years with
  materials having large band-gap energies. We describe the most common
  pixel designs and characterize their general properties.

Title: The Structure and Dynamics of the Upper Chromosphere and Lower
    Transition Region as Revealed by the Subarcsecond VAULT Observations
Authors: Vourlidas, A.; Sanchez Andrade-Nuño, B.; Landi, E.;
   Patsourakos, S.; Teriaca, L.; Schühle, U.; Korendyke, C. M.;
   Nestoras, I.
Bibcode: 2010SoPh..261...53V
Altcode: 2009arXiv0912.2272V
  The Very high Angular resolution ULtraviolet Telescope (VAULT) is a
  sounding rocket payload built to study the crucial interface between
  the solar chromosphere and the corona by observing the strongest line
  in the solar spectrum, the Ly α line at 1216 Å. In two flights, VAULT
  succeeded in obtaining the first ever subarcsecond ( 0.5\hbox{$^''$}
  ) images of this region with high sensitivity and cadence. Detailed
  analyses of those observations contributed significantly to new
  ideas about the nature of the transition region. Here, we present
  a broad overview of the Ly α atmosphere as revealed by the VAULT
  observations and bring together past results and new analyses from the
  second VAULT flight to create a synthesis of our current knowledge
  of the high-resolution Ly α Sun. We hope that this work will serve
  as a good reference for the design of upcoming Ly α telescopes and
  observing plans.

Title: Intensified solid state sensor cameras: ICCD and IAPS
Authors: Schuhle, Udo
Bibcode: 2010ISSIR...9..419S
Altcode:
  We describe the general design of intensified charge coupled devices
  and intensified active pixel sensors: cameras using microchannel plate
  intensifiers in combination with imaging arrays, like CCDs or CMOS-APS
  sensors. Several design options are compared and the capabilities and
  shortcomings of these devices will be highlighted and discussed. We
  describe, in particular, the properties of the intensifiers, phosphor
  anodes, and coupling schemes. The coupling between the intensifier
  and the image sensor is a special technological step that adds to this
  type of camera a great amount of flexibility and design options.

Title: Pre-flight calibration of LYRA, the solar VUV radiometer on
    board PROBA2
Authors: Benmoussa, A.; Dammasch, I. E.; Hochedez, J. -F.; Schühle,
   U.; Koller, S.; Stockman, Y.; Scholze, F.; Richter, M.; Kroth, U.;
   Laubis, C.; Dominique, M.; Kretzschmar, M.; Mekaoui, S.; Gissot, S.;
   Theissen, A.; Giordanengo, B.; Bolsee, D.; Hermans, C.; Gillotay,
   D.; Defise, J. -M.; Schmutz, W.
Bibcode: 2009A&A...508.1085B
Altcode:
  Aims. LYRA, the Large Yield Radiometer, is a vacuum ultraviolet
  (VUV) solar radiometer, planned to be launched in November 2009 on
  the European Space Agency PROBA2, the Project for On-Board Autonomy
  spacecraft.<BR /> Methods: The instrument was radiometrically
  calibrated in the radiometry laboratory of the Physikalisch-Technische
  Bundesanstalt (PTB) at the Berlin Electron Storage ring for SYnchroton
  radiation (BESSY II). The calibration was done using monochromatized
  synchrotron radiation at PTB's VUV and soft X-ray radiometry beamlines
  using reference detectors calibrated with the help of an electrical
  substitution radiometer as the primary detector standard.<BR /> Results:
  A total relative uncertainty of the radiometric calibration of the LYRA
  instrument between 1% and 11% was achieved. LYRA will provide irradiance
  data of the Sun in four UV passbands and with high temporal resolution
  down to 10 ms. The present state of the LYRA pre-flight calibration
  is presented as well as the expected instrument performance.<BR />

Title: Hydrogen Lyman-α and Lyman-β spectral radiance profiles in
    the quiet Sun
Authors: Tian, H.; Curdt, W.; Marsch, E.; Schühle, U.
Bibcode: 2009A&A...504..239T
Altcode: 2009arXiv0907.1069T
  Aims: We extend earlier work by studying the line profiles of the
  hydrogen Lyman-α and Lyman-β lines in the quiet Sun. They were
  obtained quasi-simultaneously in a raster scan with a size of about
  150'' × 120'' near disk center. <BR />Methods: The self-reversal depths
  of the Ly-α and Ly-β profiles. we are quantified by measuring the
  maximum spectral radiances of the two horns and the minimum spectral
  radiance of the central reversal. The information on the asymmetries
  of the Ly-α and Ly-β profiles is obtained through calculating
  the 1st and 3rd-order moments of the line profiles. By comparing
  maps of self-reversal depths and the moments with radiance images
  of the Lyman lines, photospheric magnetograms, and Dopplergrams of
  two other optically thin lines, we studied the spatial distribution
  of the Ly-α and Ly-β profiles with different self-reversal depths,
  and investigated the relationship between profile asymmetries and flows
  in the solar atmosphere. <BR />Results: We find that the emissions of
  the Lyman lines tend to be more strongly absorbed in the internetwork,
  as compared to those in the network region. Almost all of the Ly-α
  profiles are self-reversed, while about 17% of the Ly-β profiles are
  not reversed. The ratio of Ly-α and Ly-β intensities seems to be
  independent of the magnetic field strength. Most Ly-α profiles are
  stronger in the blue horn, whereas most Ly-β profiles are stronger
  in the red horn. However, the opposite asymmetries of Ly-α and
  Ly-β are not correlated pixel-to-pixel. We also confirm that when
  larger transition-region downflows are present, the Ly-α and Ly-β
  profiles are more enhanced in the blue and red horns, respectively. The
  first-order moment of Ly-β, which reflects the combined effects of
  the profile asymmetry and motion of the emitting material, strongly
  correlates with the Doppler shifts of the Si iii and O vi lines, while
  this correlation is much weaker for Ly-α. Our analysis shows that both
  Ly-α and Ly-β might be more redshifted if stronger transition-region
  downflows are present. We also find that the observed average Ly-β
  profile is redshifted with respect to its rest position.

Title: The Ly-α profile and center-to-limb variation of the quiet Sun
Authors: Curdt, W.; Tian, H.; Teriaca, L.; Schühle, U.; Lemaire, P.
Bibcode: 2008A&A...492L...9C
Altcode: 2008arXiv0812.1441C
  Aims: We study the emission of the hydrogen Lyman-α line in the quiet
  Sun, its center-to-limb variation, and its radiance distribution. We
  also compare quasi-simultaneous Ly-α and Ly-β line profiles. <BR
  />Methods: We used the high spectral and spatial resolution of the
  SUMER spectrometer and completed raster scans at various locations
  along the disk. For the first time, we used a method to reduce the
  incoming photon flux to a 20%-level by partly closing the aperture
  door. We also performed a quasi-simultaneous observation of both Ly-α
  and Ly-β at the Sun center in sit-and-stare mode. We infer the flow
  characteristic in the Ly-α map from variations in the calibrated λ
  1206 Si iii line centroids. <BR />Results: We present the average
  profile of Ly-α, its radiance distribution, its center-to-limb
  behaviour, and the signature of flows on the line profiles. Little
  center-to-limb variation and no limb brightening are observed in the
  profiles of the Ly-α line. In contrast to all other lines of the
  Lyman series, which have a red-horn asymmetry, Ly-α has a robust and
  - except for dark locations - dominating blue-horn asymmetry. There
  appears to be a brightness-to-asymmetry relationship. A similar
  and even clearer trend is observed in the downflow-to-asymmetry
  relationship. This important result is consistent with predictions
  from models that include flows. However, the absence of a clear
  center-to-limb variation in the profiles may be more indicative of
  an isotropic field than a mainly radial flow. <BR />Conclusions: It
  appears that the ubiquitous hydrogen behaves in a similar way to a
  filter that dampens all signatures of the line formation by processes
  in both the chromosphere and transition region.

Title: SWAP onboard PROBA2: An Innovative EUV Imager Designed for
    Space Weather
Authors: de Groof, A.; Berghmans, D.; Defise, J. M.; Nicula, B.;
   Schuehle, U.
Bibcode: 2008ESPM...122.116D
Altcode:
  PROBA2 (PRoject for OnBoard Autonomy) is an ESA micro-satellite
  that is being prepared for launch in 2009. Its primary goal is the
  demonstration of new technologies in the space environment. Furthermore,
  the satellite carries an ambitious suite of both in-situ and
  remote sensing instruments for monitoring space weather, despite
  the modest onboard resources. Both the spacecraft and the remote
  sensing instruments are mainly developed within Belgium. <P />One of
  the main instruments, SWAP (Sun Watcher with APS detectors and image
  Processing), is a compact EUV imager. It carries the first APS detector
  with an EUV sensitive scintillator coating to be flown in orbit. In
  addition to the new detector, the PROBA2/SWAP design is innovative
  in the sense that the instrument will make heavy use of on-board data
  processing and autonomous operations. These will range from automatic
  off-pointing and tracking of appropriate solar events, to pre-downlink
  data prioritisation, and feature and event recognition procedures. <P
  />We discuss the first results of the SWAP pre-flight calibration and
  the strengths and weaknesses of the instrument [2]. With a narrow
  spectral bandpass centred around 17.4nm, a FOV of 54 arcmin and an
  image cadence of 1 min, its design is ideal for monitoring most CME
  associated phenomena on the solar disk and close to the limb. <P />[1]
  Defise J., Halain J., Berghmans D., et al. 2007, In: Proc. SPIE, 6689,
  66890S <P />[2] De Groof A., Berghmans D., Nicula B., et al. 2008,
  Solar Phys. 249, 147-163

Title: The line profile and center-to-limb variation of quiet-Sun
    Lyman-alpha emission
Authors: Curdt, W.; Tian, H.; Teriaca, L.; Schühle, U.; Lemaire, P.
Bibcode: 2008ESPM...12.2.91C
Altcode:
  We study the emission of the hydrogen Lyman-alpha line in the quiet
  Sun, its center-to-limb variation, and its radiance distribution, which
  we also compare to the Lyman-beta line. We use the high spectral and
  spatial resolution of the SUMER spectrometer and take raster scans at
  various locations on the disk. For the first time, we have used a new
  method to reduce the incoming photon flux to a 20%-level by partly
  closing the aperture door. We also performed a quasi-simultaneous
  observation of both Ly-a and Ly-b at Sun centre in sit-and-stare
  mode. We deduce the flow characteristic in Ly-a map from variations of
  the calibrated Si III line centroids. We present the average profile
  of Ly-a, its radiance distribution, its center-to-limb behaviour,
  and the signature of flows on the line profiles. Different from all
  other lines of the Lyman series, which have a red-horn asymmetry, Ly-a
  has a robust and dominating blue-horn asymmetry. To our knowledge,
  this result is only predicted by models which include flows.

Title: CMOS-APS Detectors for Solar Physics: Lessons Learned during
    the SWAP Preflight Calibration
Authors: De Groof, A.; Berghmans, D.; Nicula, B.; Halain, J. -P.;
   Defise, J. -M.; Thibert, T.; Schühle, U.
Bibcode: 2008SoPh..249..147D
Altcode: 2008SoPh..tmp...62D
  CMOS-APS imaging detectors open new opportunities for remote sensing
  in solar physics beyond what classical CCDs can provide, offering
  far less power consumption, simpler electronics, better radiation
  hardness, and the possibility of avoiding a mechanical shutter. The
  SWAP telescope onboard the PROBA2 technology demonstration satellite
  of the European Space Agency will be the first actual implementation
  of a CMOS-APS detector for solar physics in orbit. One of the goals
  of the SWAP project is precisely to acquire experience with the
  CMOS-APS technology in a real-live space science context. Such a
  precursor mission is essential in the preparation of missions such as
  Solar Orbiter where the extra CMOS-APS functionalities will be hard
  requirements. The current paper concentrates on specific CMOS-APS
  issues that were identified during the SWAP preflight calibration
  measurements. We will discuss the different readout possibilities that
  the CMOS-APS detector of SWAP provides and their associated pros and
  cons. In particular we describe the "image lag" effect, which results in
  a contamination of each image with a remnant of the previous image. We
  have characterised this effect for the specific SWAP implementation
  and we conclude with a strategy on how to successfully circumvent the
  problem and actually take benefit of it for solar monitoring.

Title: Search for photospheric footpoints of quiet Sun transition
    region loops
Authors: Sánchez Almeida, J.; Teriaca, L.; Sütterlin, P.; Spadaro,
   D.; Schühle, U.; Rutten, R. J.
Bibcode: 2007A&A...475.1101S
Altcode: 2007arXiv0709.3451S
  Context: The footpoints of quiet Sun Transition Region (TR) loops
  do not seem to coincide with the photospheric magnetic structures
  appearing in traditional low-sensitivity magnetograms. <BR />Aims: We
  look for the so-far unidentified photospheric footpoints of TR loops
  using G-band bright points (BPs) as proxies for photospheric magnetic
  field concentrations. <BR />Methods: We compare TR measurements with
  SoHO/SUMER and photospheric magnetic field observations obtained with
  the Dutch Open Telescope. <BR />Results: Photospheric BPs are associated
  with bright TR structures, but they seem to avoid the brightest parts
  of the structure. BPs appear in regions that are globally redshifted,
  but they avoid extreme velocities. TR explosive events are not clearly
  associated with BPs. <BR />Conclusions: The observations are not
  inconsistent with the BPs being footpoints of TR loops, although we
  have not succeeded to uniquely identify particular BPs with specific
  TR loops.

Title: SWAP: a novel EUV telescope for space weather
Authors: Defise, Jean-Marc; Halain, Jean-Philippe; Berghmans,
   David; Denis, François; Mazy, Emmanuel; Thibert, Tanguy; Lecat,
   Jean-Hervé; Rochus, Pierre; Nicula, Bogdan; De Groof, Anik; Hochedez,
   Jean-François; Schühle, Udo; Ravet, Marie-Françoise; Delmotte, Frank
Bibcode: 2007SPIE.6689E..0SD
Altcode: 2007SPIE.6689E..24D
  The SWAP telescope (Sun Watcher using Active Pixel System detector and
  Image Processing) is being developed to be part of the PROBA2 payload,
  an ESA technological mission to be launched in early 2008. SWAP
  is directly derived from the concept of the EIT telescope that we
  developed in the '90s for the SOHO mission. Several major innovations
  have been introduced in the design of the instrument in order to
  be compliant with the requirements of the PROBA2 mini-satellite:
  compactness with a new of-axis optical design, radiation resistance
  with a new CMOS-APS detector, a very low power electronics, an athermal
  opto-mechanical system, optimized onboard compression schemes combined
  with prioritization of collected data, autonomy with automatic
  triggering of observation and off-pointing procedures in case of
  Solar event occurrence, ... All these new features result from the low
  resource requirements (power, mass, telemetry) of the mini-satellite,
  but also take advantage of the specificities of a modern technological
  platform, such as quick pointing agility, new powerful on-board
  processor, Packetwire interface and autonomous operations. These
  new enhancements will greatly improve the operations of SWAP as
  a space weather sentinel from a low Earth orbit while the downlink
  capabilities are limited. This paper summarizes the conceptual design,
  the development and the qualification of the instrument, the autonomous
  operations and the expected performances for science exploitation.

Title: Multi-wavelength Analysis of a Quiet Solar Region
Authors: Tsiropoula, G.; Tziotziou, K.; Giannikakis, J.; Young, P.;
   Schühle, U.; Heinzel, P.
Bibcode: 2007ASPC..368..171T
Altcode: 2007arXiv0704.1592T
  We present observations of a solar quiet region obtained by the
  ground-based Dutch Open Telescope (DOT), and by instruments on the
  spacecraft SOHO and TRACE. The observations were obtained during a
  coordinated observing campaign on October 2005. The aim of this work
  is to present the rich diversity of fine-scale structures that are
  found at the network boundaries and their appearance in different
  instruments and different spectral lines that span the photosphere
  to the corona. Detailed studies of these structures are crucial to
  understanding their dynamics in different solar layers, as well as
  the role such structures play in the mass balance and heating of the
  solar atmosphere.

Title: T he Lower Transition Region As Seen In The H I Lyman-α Line
Authors: Teriaca, L.; Schühle, U.; Solanki, S. K.; Curdt, W.;
   Marsch, E.
Bibcode: 2007ESASP.641E..84T
Altcode:
  The SUMER spectrometer aboard SOHO has been used to acquire several
  raster images and temporal series of quiet-Sun targets at both disk
  centre and the limb. Spectra have been recorded simultaneously in the
  H I Lyman α and the Si III 120.6 nm line. Both spatial and temporal
  maps of the integrated radiances appear very similar in the two lines,
  despite the huge difference in optical thickness, a result showing the
  H I Lyman α to be a good diagnostic of the dynamics and morphology of
  the lower transition region. Oscillations can be detected and studied
  at all observed locations. At disk centre, the 3 minute oscillations are
  sporadically observed in the inter-network but also at locations at the
  edges of network lanes, while 5 minute oscillations clearly dominate
  the network. At the limb, evidence of 3 to 5 minute oscillations is
  found at the base of spicules. Moreover, H I Lyman α spectra shows a
  high degree of variability, revealing also the signature of explosive
  events. The combination of high spectral purity images and slit spectra
  in the H I Lyman α line would therefore be an exceptional new tool
  to investigate the nature of the solar transition region. This line
  is therefore of interest for both, a high resolution channel in the
  EUI instrument and for the EUS spectrometer.

Title: T he Lower Transitio n Region As Seen In The H I Lyman-α Line.
Authors: Teriaca, L.; Schühle, U.; Solanki, S. K.; Curdt, W.;
   Marsch, E.
Bibcode: 2007ESASP.641E..36T
Altcode:
  The SUMER spectrometer aboard SOHO has been used to acquire several
  raster images and temporal series of quiet-Sun targets at both disk
  centre and the limb. Spectra have been recorded simultaneously in the
  H I Lyman α and the Si III 120.6 nm line. Both spatial and temporal
  maps of the integrated radiances appear very similar in the two lines,
  despite the huge difference in optical thickness, a result showing the
  H I Lyman α to be a good diagnostic of the dynamics and morphology of
  the lower transition region. Oscillations can be detected and studied
  at all observed locations. At disk centre, the 3 minute oscillations are
  sporadically observed in the inter-network but also at locations at the
  edges of network lanes, while 5 minute oscillations clearly dominate
  the network. At the limb, evidence of 3 to 5 minute oscillations is
  found at the base of spicules. Moreover, H I Lyman α spectra shows a
  high degree of variability, revealing also the signature of explosive
  events. The combination of high spectral purity images and slit spectra
  in the H I Lyman α line would therefore be an exceptional new tool
  to investigate the nature of the solar transition region. This line
  is therefore of interest for both, a high resolution channel in the
  EUI instrument and for the EUS spectrometer.

Title: T hin Silicon Carbide Coating Of The Primary Mirror Of VUV
    Imaging Instruments Of Solar Orbiter
Authors: Schühle, U.; Uhlig, H.; Curdt, W.; Feigl, T.; Theissen,
   A.; Teriaca, L.
Bibcode: 2007ESASP.641E..83S
Altcode:
  We investigate the thermo-optical and vacuum- ultraviolet properties of
  thin silicon carbide (SiC) coatings on transparent substrates in view of
  their use for Solar Orbiter remote sensing VUV instrumentation. We have
  made experimental studies with thin SiC coatings on quartz plates to
  evaluate their reflective properties in the VUV spectral range between
  58 nm and 123 nm. We discuss the results in relation to the visible
  and near infrared optical properties of the samples. A thin SiC coating
  of 10 nm thickness is shown to be a very promising compromise between
  high VUV reflectivity and low vis/IR absorption. The overall absorption
  of the solar spectrum by such a mirror is less than 8 %. This will be
  beneficial for instruments requiring a large aperture due to diffraction
  and radiometric limitation, in coping with the thermal heat load during
  the Solar Orbiter mission. As an example, we propose a design of the
  primary telescope mirror for the Extreme Ultraviolet Spectrometer (EUS).

Title: EUI, The Ultraviolet Imaging Telescopes Of Solar Orbiter
Authors: Hochedez, J. -F.; Appourchaux, T.; Defise, J. -M.; Harra,
   L. K.; Schühle, U.; Auchère, F.; Curdt, W.; Hancock, B.; Kretzschmar,
   M.; Lawrence, G.; Leclec'h, J. -C.; Marsch, E.; Mercier, R.; Parenti,
   S.; Podladchikova, E.; Ravet, M. -F.; Rochus, P.; Rodriguez, L.;
   Rouesnel, F.; Solanki, S.; Teriaca, L.; Van Driel, L.; Vial, J. -C.;
   Winter, B.; Zhukov, A.
Bibcode: 2007ESASP.641E..33H
Altcode:
  The scientific objectives of Solar Orbiter rely ubiquitously on EUI,
  its suite of solar atmosphere imaging telescopes. In the configuration
  discussed here, EUI includes three co-aligned High Resolution Imagers
  (HRI) and one Full Sun Imager (FSI). FSI and two HRIs observe in extreme
  ultraviolet passbands, dominated by coronal emission. Another HRI is
  designed for the hydrogen Lyman α radiation in the far UV, imaging the
  Chromosphere and the lower Transition Region. The current EUI design
  and some of its development challenges are highlighted. EUI profits from
  co-rotation phases, solar proximity and departure from the ecliptic. In
  synergy with the other S.O. payload, EUI probes the dynamics of the
  solar atmosphere, provides context data for all investigations and helps
  to link in-situ and remote-sensing observations. In short, it serves all
  four top-level goals of the mission. For these reasons, the EUI suite
  is keenly anticipated in the European scientific community and beyond.

Title: Instrumental Approaches To Achieve The Measurements Required
    For Exploring The Energetics, Dynamics A nd Fine-Scale Structure Of
    The Sun's Magnetized Atmosphere
Authors: Schühle, U.
Bibcode: 2007ESASP.641E..17S
Altcode:
  An overview is given about the technical implementation of the remote
  sensing instrumentation of the Solar Orbiter mission. We will discuss
  the "science implementation" related to the specific scientific goal
  "Explore the energetics, dynamics and fine-scale structure of the
  Sun's magnetized atmosphere". The technical approaches to implement the
  observational scenarios outlined in the Science Requirements Document
  (SRD) are reviewed. Some technical design options proposed for the
  remote sensing instruments will be shown in detail and some open
  technical issues are highlighted in regard to answering the question
  "How do we achieve this goal?".

Title: Optical Design Of The Extreme Ultraviolet Spectrometer (EUS)
    On Board Solar Orbiter
Authors: Middleton, K.; Da Deppo, V.; Poletto, L.; Schühle, U.;
   Thomas, R. J.; Young, P. R.
Bibcode: 2007ESASP.641E..48M
Altcode:
  We present optical designs for the Extreme Ultraviolet Imaging
  Spectrometer (EUS) proposed for Solar Orbiter. We summarise the
  scientific requirements for EUS and show how they translate into an
  instrument specification and optical design. Two design options are
  presented: one utilising a normal incidence telescope and one utilising
  a grazing incidence telescope. Both options use the same design of
  spectrometer, which incorporates a Toroidal Varied Line-Space (TVLS)
  grating, allowing high quality imaging at relatively large spectrometer
  magnifications. This results in a very compact yet high performance
  design. We give estimates of the instrument's optical performance and
  throughput and discuss briefly some heat management strategies.

Title: LYRA - a solar UV radiometer using diamond detectors
Authors: Theissen, A.; Benmoussa, A.; Schühle, U.; Hochedez, J. -F.;
   Schmutz, W.
Bibcode: 2007msfa.conf...27T
Altcode:
  LYRA, the Lyman-α radiometer, is a highcadence (100 Hz) solar
  VUV radiometer which will measure diskintegrated irradiances in 4
  wavelength channels. Special emphasis is given on novel detectors based
  on diamond which will be tested for the first time in space. Two kinds
  of detectors are employed: MSM and PiNtype detectors. Their particular
  advantage compared to silicon detectors lies in their solar blindness
  with a UV/visible reduction ratio of at least four orders of magnitude,
  which simplifies the design of UV instruments.

Title: S pace Qualification Of A Thin Wafer Lithium Niobate Etalon
    For The Visible Light Imager And Magnetograph (Vim)
Authors: Schühle, U.; Mathew, S. K.; Wedemeier, M.; Hartwig, H.;
   Ballesteros, E.; Martinez Pillet, V.; Solanki, S. K.
Bibcode: 2007ESASP.641E..82S
Altcode:
  For the Visible Light Imager and Magnetograph (VIM) a high-resolution
  filtergraph is under design. The system takes advantage of a lithium
  niobate (LiNbO3) crystal which can be used as a scanning filter using
  high voltage for tuning. We have undertaken first studies to qualify
  a lithium niobate wafer of 70 mm aperture size for deployment and use
  in space. We show the results of the mechanical mounting and vibration
  and thermal cycling tests as well as stability tests under fast voltage
  tuning in vacuum. Although these tests have all been very successful,
  further environmental testing is necessary to fully space-qualify the
  filter for the Solar Orbiter mission.

Title: Solar Coronal Magnetic Field Mapper
Authors: Solanki, S. K.; Raouafi, N. -E.; Gandorfer, A.; Schühle,
   U.; Lagg, A.
Bibcode: 2006ESASP.617E.160S
Altcode: 2006soho...17E.160S
  No abstract at ADS

Title: Hα Chromospheric Mottles and their UV/EUV Counterparts Seen
    by SOHO/Sumer
Authors: Tziotziou, K.; Heinzel, P.; Tsiropoula, G.; Schühle, U.
Bibcode: 2006ESASP.617E.112T
Altcode: 2006soho...17E.112T
  No abstract at ADS

Title: The Dynamic Nature of the Lower Transition Region as Revealed
    by Spectroscopy of the Hydrogen Lyman-α Line
Authors: Teriaca, L.; Schühle, U.; Solanki, S. K.; Curdt, W.;
   Marsch, E.
Bibcode: 2006ESASP.617E..77T
Altcode: 2006soho...17E..77T
  No abstract at ADS

Title: Prominence Parameters Derived from Hydrogen Lyman-α Spectral
    Profiles Measured by SOHO/SUMER
Authors: Gunár, S.; Teriaca, L.; Heinzel, P.; Schühle, U.
Bibcode: 2006ESASP.617E..63G
Altcode: 2006soho...17E..63G
  No abstract at ADS

Title: LYRA, a solar UV radiometer on Proba2
Authors: Hochedez, J. -F.; Schmutz, W.; Stockman, Y.; Schühle, U.;
   Benmoussa, A.; Koller, S.; Haenen, K.; Berghmans, D.; Defise, J. -M.;
   Halain, J. -P.; Theissen, A.; Delouille, V.; Slemzin, V.; Gillotay, D.;
   Fussen, D.; Dominique, M.; Vanhellemont, F.; McMullin, D.; Kretzschmar,
   M.; Mitrofanov, A.; Nicula, B.; Wauters, L.; Roth, H.; Rozanov, E.;
   Rüedi, I.; Wehrli, C.; Soltani, A.; Amano, H.; van der Linden, R.;
   Zhukov, A.; Clette, F.; Koizumi, S.; Mortet, V.; Remes, Z.; Petersen,
   R.; Nesládek, M.; D'Olieslaeger, M.; Roggen, J.; Rochus, P.
Bibcode: 2006AdSpR..37..303H
Altcode:
  LYRA is the solar UV radiometer that will embark in 2006 onboard
  Proba2, a technologically oriented ESA micro-mission. LYRA is
  designed and manufactured by a Belgian Swiss German consortium (ROB,
  PMOD/WRC, IMOMEC, CSL, MPS and BISA) with additional international
  collaborations. It will monitor the solar irradiance in four UV
  passbands. They have been chosen for their relevance to Solar Physics,
  Aeronomy and Space Weather: (1) the 115 125 nm Lyman-α channel,
  (2) the 200 220 nm Herzberg continuum range, (3) the Aluminium
  filter channel (17 70 nm) including He II at 30.4 nm and (4) the
  Zirconium filter channel (1 20 nm). The radiometric calibration will
  be traceable to synchrotron source standards (PTB and NIST). The
  stability will be monitored by onboard calibration sources (LEDs),
  which allow to distinguish between potential degradations of the
  detectors and filters. Additionally, a redundancy strategy maximizes
  the accuracy and the stability of the measurements. LYRA will benefit
  from wide bandgap detectors based on diamond: it will be the first space
  assessment of a pioneering UV detectors program. Diamond sensors make
  the instruments radiation-hard and solar-blind: their high bandgap
  energy makes them insensitive to visible light and, therefore, make
  dispensable visible light blocking filters, which seriously attenuate
  the desired ultraviolet signal. Their elimination augments the effective
  area and hence the signal-to-noise, therefore increasing the precision
  and the cadence. The SWAP EUV imaging telescope will operate next to
  LYRA on Proba2. Together, they will establish a high performance solar
  monitor for operational space weather nowcasting and research. LYRA
  demonstrates technologies important for future missions such as the
  ESA Solar Orbiter.

Title: SWAP onboard PROBA 2, a new EUV imager for solar monitoring
Authors: Berghmans, D.; Hochedez, J. F.; Defise, J. M.; Lecat, J. H.;
   Nicula, B.; Slemzin, V.; Lawrence, G.; Katsyiannis, A. C.; van der
   Linden, R.; Zhukov, A.; Clette, F.; Rochus, P.; Mazy, E.; Thibert,
   T.; Nicolosi, P.; Pelizzo, M. -G.; Schühle, U.
Bibcode: 2006AdSpR..38.1807B
Altcode:
  SWAP (Sun Watcher using Active Pixel system detector and image
  processing) is a solar imager in the extreme ultraviolet (EUV)
  that has been selected to fly in 2007 on the PROBA 2 technological
  platform, an ESA program. SWAP will use an off-axis Ritchey Chrétien
  telescope equipped with an EUV enhanced active pixel sensor detector
  (coated APS). This type of detector has advantages that promise to
  be very profitable for solar EUV imaging. SWAP will provide solar
  coronal images at a 1-min cadence in a bandpass centered on 17.5
  nm. Observations with this specific wavelength allow detecting
  phenomena, such as solar flares or EIT-waves, associated with the
  early phase of coronal mass ejections. Image processing software will
  be developed that automatically detects these phenomena and sends out
  space weather warnings. Together with its sister instrument LYRA, also
  onboard PROBA 2, SWAP will serve as a high performance solar monitoring
  tool to be used in operational space weather forecasting. The SWAP
  data will complement the solar observations provided by instruments
  like SOHO-EIT, and STEREO-SECCHI.

Title: The Dynamics of the Lower Transition Region as Inferred from
    Spectroscopy of the Hydrogen LYMAN-α Line
Authors: Teriaca, L.; Schühle, U.; Solanki, S. K.; Curdt, W.;
   Marsch, E.
Bibcode: 2005ESASP.600E.100T
Altcode: 2005ESPM...11..100T; 2005dysu.confE.100T
  No abstract at ADS

Title: A new relation between the central spectral solar H I Lyman
    α irradiance and the line irradiance measured by SUMER/SOHO during
    the cycle 23
Authors: Emerich, Claude; Lemaire, Philippe; Vial, Jean-Claude; Curdt,
   Werner; Schühle, Udo; Wilhelm, Klaus
Bibcode: 2005Icar..178..429E
Altcode:
  The spectral irradiance at the center of the solar H I Lyman α
  ( λ=121.5664nm, referred to as Lyα in this paper) line profile
  is the main excitation source responsible for the atomic hydrogen
  resonant scattering of cool material in our Solar System. It has
  therefore to be known with the best possible accuracy in order to
  model the various Lyα emissions taking place in planetary, cometary,
  and interplanetary environments. Since the only permanently monitored
  solar irradiance is the total one (i.e. integrated over the whole
  Lyα line profile), Vidal-Madjar [1975. Evolution of the solar Lyman
  alpha flux during four consecutive years. Solar Phys. 40, 69-86] using
  Orbiting Solar Observatory 5 (OSO-5) satellite Lyα data, established
  a semi-empirical formula allowing him to deduce the central spectral
  Lyα irradiance from the total one. This relation has been extensively
  used for three decades. But, at the low altitude of the OSO-5 orbit,
  the central part of the solar line profile was deeply absorbed by a
  large column of exospheric atomic hydrogen. Consequently, the spectral
  irradiance at the center of the line was obtained by a complex procedure
  confronting the observations with simulations of both the geocoronal
  absorption and the self-reversed shape of the solar Lyα profile. The
  SUMER spectrometer onboard SOHO positioned well outside the hydrogen
  geocorona, provided full-Sun Lyα profiles, not affected by such an
  absorption [Lemaire et al., 1998. Solar H I Lyman α full disk profile
  obtained with the SUMER/SOHO spectrometer. Astron. Astrophys. 334,
  1095-1098; 2002. Variation of the full Sun Hydrogen Lyman α and β
  profiles with the activity cycle. Proc. SOHO 11 Symposium, ESA SP-508,
  219-222; 2004. Variation of the full Sun Hydrogen Lyman profiles
  through solar cycle 23. COSPAR 2004 Meeting], making it—for the first
  time—possible to measure the spectral and total Lyα solar irradiances
  directly and simultaneously. A new relation between these two quantities
  is derived in an expression that is formally similar to the previous
  one, but with significantly different parameters. After having discussed
  the potential causes for such differences, it is suggested that the
  new relation should replace the old one for any future modeling of the
  numerous Lyα absorptions and emissions observed in the Solar System.

Title: The Structure of the Lower Transition Region as Inferred from
    the Hydrogen LYMAN-α Line Radiance
Authors: Teriaca, L.; Schühle, U.; Solanki, S. K.; Curdt, W.;
   Marsch, E.
Bibcode: 2005ESASP.596E..66T
Altcode: 2005ccmf.confE..66T
  No abstract at ADS

Title: On the nature of the unidentified solar emission near 117 nm
Authors: Wilhelm, K.; Schühle, U.; Curdt, W.; Hilchenbach, M.;
   Marsch, E.; Lemaire, P.; Bertaux, J. -L.; Jordan, S. D.; Feldman, U.
Bibcode: 2005A&A...439..701W
Altcode:
  Spectral observations of the Sun in the vacuum-ultraviolet wavelength
  range by SUMER on SOHO led to the discovery of unusual emission
  features - called humps here - at 116.70 nm and 117.05 nm on either
  side of the He i 58.43 nm line. This resonance line is seen in the
  second order of diffraction, whereas the humps are recorded in the
  first order with the SUMER spectrometer. In its spectra both orders
  are superimposed. Two less pronounced humps can be detected at 117.27
  nm and near 117.85 nm. After rejecting various possibilities of an
  instrumental cause of the humps, they are studied in different solar
  regions. Most of the measurements, in particular those related to the
  limb-brightening characteristics, indicate that the humps are not part
  of the background continuum. An assembly of spectrally-unresolved atomic
  or ionic emission lines might be contributing to the hump at 117.05
  nm, but no such lines are known near 116.7 nm. It is concluded that we
  detect genuine radiation, the generation of which is not understood. A
  two-photon emission process, parametric frequency down conversion,
  and molecular emissions are briefly considered as causes of the humps,
  but a final conclusion could not be reached.

Title: Variation of the full Sun hydrogen Lyman profiles through
    solar cycle 23
Authors: Lemaire, P.; Emerich, C.; Vial, J. -C.; Curdt, W.; Schühle,
   U.; Wilhelm, K.
Bibcode: 2005AdSpR..35..384L
Altcode:
  The hydrogen Lyman (Lyα, 121.267 nm and Lyβ, 102.572 nm) lines are
  important contributors to the solar extreme ultra violet (EUV) flux
  which illuminates the upper Earth’s atmosphere. From high resolution
  spectral observations performed with the solar ultraviolet measurement
  of emitted radiations (SUMER) spectrometer on the Solar and Heliospheric
  Observatory (SOHO), the detailed profiles of these two lines have been
  obtained. Some insights into the variation of the shape of the profiles,
  sampled throughout the present solar cycle 23, are given and discussed.

Title: SWAP: Sun watcher with a new EUV telescope on a technology
    demonstration platform
Authors: Defise, Jean-Marc; Lecat, Jean-Hervé; Mazy, Emmanuel;
   Rochus, Pierre; Rossi, Laurence; Thibert, Tanguy; Gillis, Jean-Marie;
   Berghmans, David; Hochedez, Jean-François; Schühle, Udo
Bibcode: 2004ESASP.554..257D
Altcode: 2004icso.conf..257D
  SWAP (SWAP (Sun Watcher using Active Pixel System detector and Image
  Processing) is an instrument that has been selected to fly on the
  PROBA-2 technology demonstration platform, a program of the European
  Space Agency (ESA) to be launched in 2006. SWAP is based on an off-axis
  degraded Ritchey Chretien telescope that will image the EUV solar
  corona at 19.5 nm on a specifically fabricated extreme ultraviolet
  (EUV) sensitivity enhanced CMOS APS detector. The optical design and
  the optical coatings are derived from the Extreme Ultraviolet Imaging
  Telescope (EIT) operating on-board SOHO since 1995. It has been adapted
  for a single wavelength telescope with off-axis optics. It allows to
  use smaller optics and filters, with simple internal baffles avoiding
  external protruding parts. The superpolished optics will receive a
  multilayer coating that provides spectral selection centred on 19.5
  nm and EUV reflectivity in normal incidence. This compact design is
  specifically adapted for accommodation on PROBA-2, where mass and
  envelope requirements are very stringent The SWAP PROBA-2 program will
  be an opportunity to demonstrate this new optical concept, while it
  will also validate space remote sensing with APS detectors, as well as
  on-board image processing capabilities. On the science outcomes, SWAP
  will provide solar corona images in the Fe XII line on a baselined 2-min
  cadence. Observations with this specific wavelength allow detecting
  phenomena, such as solar flares or 'EIT-waves', associated with the
  early phase of coronal mass ejections. The SWAP data will complement
  the observations provided by SOHO-EIT, and STEREO-SECCHI.

Title: A New Relation between Central and Total Solar H I Lyman-α
    Irradiances, as measured by SOHO during Solar Cycle 23 (1996-2003)
Authors: Emerich, C.; Lemaire, P.; Vial, J. -C.; Curdt, W.; Schüle,
   U.; Wilhelm, K.
Bibcode: 2004AAS...204.9802E
Altcode: 2004BAAS...36..984E
  The spectral irradiance at the center of the solar H Ly-α line profile
  is the main excitation source responsible for the atomic hydrogen
  resonant scattering in cool material. It has therefore to be known
  with the best possible accuracy to model the H Ly-α emissions taking
  place in planetary, cometary and interplanetary environments. On
  the other hand, the only permanently monitored solar irradiance is
  the total one - either measured by near-Earth satellites, or deduced
  from its correlation with solar activity indexes. It is the reason why
  Vidal-Madjar (1975) using OSO-5 satellite H Ly-α data, established a
  semi-empirical formula allowing to deduce the central H Ly-α irradiance
  from the integrated one. This relation has been extensively used for
  three decades. In fact, at the low altitude of the OSO-5 orbit, the
  observed central part of the solar line profiles was deeply absorbed by
  a large column of exospheric atomic hydrogen. Consequently, the solar
  line center irradiances were not measured directly, but obtained by
  confronting the measurements with simulations of both the geocoronal
  absorption and the self-reversed shape of the central solar profile
  itself. <P />On the contrary, the SOHO/SUMER spectrometer orbiting well
  outside the H geocoronal envelope (at the L1 Sun-Earth Lagrange point),
  provided full Sun H Ly-α profiles, exempt from any central geocoronal
  absorption (Lemaire et al. (1998, 2002, 2004)). This has made it
  possible to directly measure the central H Ly-α solar irradiances
  as a function of the integrated ones, during eight years of Solar
  Cycle 23. The newly obtained relation confirms the general trend of
  the previous one, but it is characterized by significantly different
  coefficients. It will therefore provide new and more accurate inputs
  for the future modeling of the various Ly-α emissions occurring inside
  the Solar System.

Title: Flare observation of the Sun as a star by SUMER/SOHO in the
    hydrogen Lyman continuum
Authors: Lemaire, P.; Gouttebroze, P.; Vial, J. -C.; Curdt, W.;
   Schühle, U.; Wilhelm, K.
Bibcode: 2004A&A...418..737L
Altcode:
  During the execution of the programme ``Sun as a star'', while the
  SUMER (Solar Ultraviolet Emission of Emitted Radiation)/SOHO (SOlar and
  Heliospheric Observatory) slit was collecting the scattered radiation
  from the telescope mirror far away from the solar disk image, a class
  X5.3/3b flare erupted on the solar disk, on 25 August 2001. During
  the first phase of the flare a relative increase of a few percent was
  detected at the head of the hydrogen Lyman continuum. After correction
  from the instrumental parameters, the relative signal increase is 70%
  at the head of the Lyman continuum (910 Å), and 190% in the C II 904
  Å multiplet. Accounting for the area of the flare region, the local
  increase of the radiance of the Lyman continuum and of the C II lines
  is estimated to be a factor of several thousands. We compare this
  result with other solar observations and models. <P />Appendix A is
  only available in electronic form at http://www.edpsciences.org

Title: Development of imaging arrays for solar UV observations based
    on wide band gap materials
Authors: Schuehle, Udo H.; Hochedez, Jean-Francois E.; Pau, Jose Luis;
   Rivera, Carlos; Munoz, Elias; Alvarez, Jose; Kleider, Jean-Paul;
   Lemaire, Philippe; Appourchaux, Thierry; Fleck, Bernhard; Peacock,
   Anthony; Richter, Mathias; Kroth, Udo; Gottwald, Alexander; Castex,
   Marie-Claude; Deneuville, Alain; Muret, Pierre; Nesladek, Milos;
   Omnes, Franck; John, Joachim; Van Hoof, Chris
Bibcode: 2004SPIE.5171..231S
Altcode:
  Solar ultraviolet imaging instruments in space pose most demanding
  requirements on their detectors in terms of dynamic range, low noise,
  high speed, and high resolution. Yet UV detectors used on missions
  presently in space have major drawbacks limiting their performance
  and stability. In view of future solar space missions we have started
  the development of new imaging array devices based on wide band gap
  materials (WBGM), for which the expected benefits of the new sensors -
  primarily visible blindness and radiation hardness - will be highly
  valuable. Within this initiative, called "Blind to Optical Light
  Detectors (BOLD)", we have investigated devices made of AlGa-nitrides
  and diamond. We present results of the responsivity measurements
  extending from the visible down to extreme UV wavelengths. We discuss
  the possible benefits of these new devices and point out ways to build
  new imaging arrays for future space missions.

Title: SWAP: Sun watcher using APS detector on-board PROBA-2, a new
    EUV off-axis telescope on a technology demonstration platform
Authors: Defise, Jean-Marc; Berghmans, David; Hochedez, Jean-Francois
   E.; Lecat, Jean-Herve M.; Mazy, Emmanuel; Rochus, Pierre L.; Thibert,
   Tanguy; Nicolosi, Piergiorgio; Pelizzo, Maria G.; Schuehle, Udo H.;
   Van der Linden, Ronald A. M.; Zhukov, Andrei N.
Bibcode: 2004SPIE.5171..143D
Altcode:
  SWAP (Sun Watcher using Active Pixel System detector and Image
  Processing) is an instrument that has been selected to fly on the
  PROBA-II technology demonstration platform, a program of the European
  Space Agency (ESA) to be launched in 2006. This paper presents the
  instrument concept and its scientific goals. SWAP uses an off-axis
  Ritchey Chretien telescope that will image the EUV solar corona at 19.5
  nm on a specifically fabricated extreme ultraviolet (EUV) sensitivity
  enhanced CMOS APS detector. This type of detector has advantages that
  promise to be very profitable for solar EUV imaging. The SWAP design
  is built on a similar concept as the MAGRITTE instrument suite for
  the NASA Solar Dynamics Observatory (SDO) mission to be launched in
  2007. The optics have been adapted to the detector size. The SWAP
  PROBA-2 program will be an opportunity to demonstrate and validate
  the optical concept of MAGRITTE, while it will also validate space
  remote sensing with APS detectors. On the science outcomes, SWAP will
  provide solar corona images in the Fe XII line on a baselined 1-min
  cadence. Observations with this specific wavelength allow detecting
  phenomena, such as solar flares or 'EIT-waves", associated with the
  early phase of coronal mass ejections. Image recognition software will
  be developed that automatically detects these phenomena and sends out
  space weather warnings. Different modules of this software will run
  both on the ground system as well as on the onboard computer of PROBA
  II. The SWAP data will complement the observations provided by SOHO-EIT,
  and STEREO-SECCHI.

Title: MAGRITTE: an instrument suite for the solar atmospheric
    imaging assembly (AIA) aboard the Solar Dynamics Observatory
Authors: Rochus, Pierre L.; Defise, Jean-Marc; Halain, Jean-Philippe;
   Jamar, Claude A. J.; Mazy, Emmanuel; Rossi, Laurence; Thibert,
   Tanguy; Clette, Frederic; Cugnon, Pierre; Berghmans, David; Hochedez,
   Jean-Francois E.; Delaboudiniere, Jean-Pierre; Auchere, Frederic;
   Mercier, Raymond; Ravet, Marie-Francoise; Delmotte, Franck; Idir,
   Mourad; Schuehle, Udo H.; Bothmer, Volker; Fineschi, Silvano; Howard,
   Russell A.; Moses, John D.; Newmark, Jeffrey S.
Bibcode: 2004SPIE.5171...53R
Altcode:
  The Solar Atmospheric Imaging Assembly (AIA) aboard the Solar Dynamics
  Observatory will characterize the dynamical evolution of the solar
  plasma from the chromosphere to the corona, and will follow the
  connection of plasma dynamics with magnetic activity throughout the
  solar atmosphere. The AIA consists of 7 high-resolution imaging
  telescopes in the following spectral bandpasses: 1215Å. Ly-a,
  304 Å He II, 629 Å OV, 465 Å Ne VII, 195 Å Fe XII (includes Fe
  XXIV), 284 Å Fe XV, and 335 Å Fe XVI. The telescopes are grouped
  by instrumental approach: the MAGRITTE Filtergraphs (R. MAGRITTE,
  famous 20th Century Belgian Surrealistic Artist), five multilayer EUV
  channels with bandpasses ranging from 195 to 1216 Å, and the SPECTRE
  Spectroheliograph with one soft-EUV channel at OV 629 Å. They will be
  simultaneously operated with a 10-second imaging cadence. These two
  instruments, the electronic boxes and two redundant Guide Telescopes
  (GT) constitute the AIA suite. They will be mounted and coaligned on a
  dedicated common optical bench. The GTs will provide pointing jitter
  information to the whole SHARPP assembly. This paper presents the
  selected technologies, the different challenges, the trade-offs to be
  made in phase A, and the model philosophy. From a scientific viewpoint,
  the unique combination high temporal and spatial resolutions with the
  simultaneous multi-channel capability will allow MAGRITTE / SPECTRE
  to explore new domains in the dynamics of the solar atmosphere, in
  particular the fast small-scale phenomena. We show how the spectral
  channels of the different instruments were derived to fulfill the
  AIA scientific objectives, and we outline how this imager array will
  address key science issues, like the transition region and coronal waves
  or flare precursors, in coordination with other SDO experiments. We
  finally describe the real-time solar monitoring products that will be
  made available for space-weather forecasting applications.

Title: Variation of the full Sun hydrogen Lyman profiles through
    solar cycle 23
Authors: Lemaire, P.; Emerich, C.; Vial, J. -C.; Curdt, W.; Schühle,
   U.; Wilhelm, K.
Bibcode: 2004cosp...35..510L
Altcode: 2004cosp.meet..510L
  The hydrogen Lyman (121.267 nm and 102.572 nm) lines are important
  contributors to the solar EUV flux which illuminates the upper Earth's
  atmosphere. From high resolution spectral observations performed with
  the SUMER FUV-EUV spectrometer on SoHO, the detailed profiles of these
  two lines have been obtained. Some insights into the variation of the
  shape of the profiles, sampled throughout the present solar cycle 23,
  are shown and discussed.

Title: Calibration of space instrumentation with synchrotron radiation
Authors: Richter, M.; Gottwald, A.; Scholze, F.; Schühle, U.; Ulm, G.
Bibcode: 2004cosp...35.1938R
Altcode: 2004cosp.meet.1938R
  The Physikalisch-Technische Bundesanstalt (PTB) is Germany's national
  metrology institute providing scientific and technical services. For
  more than 20 years, PTB has used synchrotron radiation at the electron
  storage rings BESSY I and BESSY II for photon metrology in the
  spectral range from UV radiation to X-rays, e.g. for the calibration
  of radiation sources, detectors, and spectrometers as well as for
  the characterization of optical components. Most of the measurements
  are based on two different primary standards, electron storage
  rings as primary radiation source standards and cryogenic electrical
  substitution radiometers as primary detector standards. Many activities
  are related to radiometric calibrations of space-based instruments for
  extraterrestrial, solar, and astronomical missions. Outstanding examples
  have been the calibration of the SUMER and CDS spectrographs of the
  SOHO mission, X-ray detector calibrations for the X-ray observatories
  Chandra and XMM-Newton, and the calibration of Lyman-alpha detectors
  for the NASA satellites TWINS. This contribution presents examples from
  recent work, in particular within the framework of the ESA projects
  PROBA 2 and Solar Orbiter.

Title: Solar-Blind Diamond Detectors for Lyra, the Solar VUV
    Radiometer on Board Proba II
Authors: Benmoussa, A.; Hochedez, J. -F.; Schmutz, W. K.; Schühle,
   U.; Nesládek, M.; Stockman, Y.; Kroth, U.; Richter, M.; Theissen,
   A.; Remes, Z.; Haenen, K.; Mortet, V.; Koller, S.; Halain, J. P.;
   Petersen, R.; Dominique, M.; D'Olieslaeger, M.
Bibcode: 2003ExA....16..141B
Altcode:
  Fabrication, packaging and experimental results on the calibration
  of metal-semiconductor-metal (MSM) photodetectors made on diamond
  are reported. LYRA (Lyman-α RAdiometer onboard PROBA-2) will use
  diamond detectors for the first time in space for a solar physics
  instrument. A set of measurement campaigns was designed to obtain the
  XUV-to-VIS responsivity of the devices and other characterizations. The
  measurements of responsivity in EUV and VUV spectral ranges (40 240
  nm) have been carried out by the Physkalisch-Technische Bundesanstalt
  (PTB) in Germany at the electron storage ring BESSY II. The longer
  wavelength range from 210 to 1127 nm was measured with monochromatic
  light by using a Xe-lamp at IMO-IMOMEC. The diamond detectors exhibit a
  photoresponse which lie in the 35 65 mA/W range at 200 nm (corresponding
  to an external quantum efficiency of 20 40%) and indicate a visible
  rejection ratio (200 500 nm) higher than four orders of magnitude.

Title: Cleanliness and calibration stability of UV instruments on SOHO
Authors: Schuehle, Udo H.
Bibcode: 2003SPIE.4853...88S
Altcode:
  Optical instruments for solar observations from space have in the past
  suffered from degradation of responsivity caused by contamination from
  various materials used in spacecraft and instrument construction. This
  was particularly detrimental in the ultraviolet range of the spectrum
  where the solar irradiance is weak, compared to the visible, yet strong
  enough to cause polymerization of organic contaminants on optical
  surfaces that are continuously exposed. The Solar and Heliospheric
  Observatory (SOHO) mission could largely avoid such effects. Material
  selection and special design features of instruments and spacecraft
  contributed mostly to this success. The various kinds of remote sensing
  instruments on SOHO have achieved a stability of their responsivity
  through special cleanliness requirements. This contribution will
  highlight those design aspects which are generally useful for future
  solar missions. Analysis of instrument responsivity data shows that
  under these circumstances the stability was actually not limited
  by contamination but by the instabilities inherent to the present
  detector technology.

Title: Intercalibration of SUMER and CDS on SOHO. III. SUMER and
    CDS-GIS
Authors: Pauluhn, Anuschka; Lang, Jim; Breeveld, Eddie R.; Solanki,
   Sami K.; Schühle, Udo
Bibcode: 2003ApOpt..42..657P
Altcode:
  Simultaneous observation of the same solar sources with different
  instruments is one way to test prelaunch radiometric calibrations and
  to detect changes in responsivity with time of extreme-ultraviolet
  instruments in space. Here we present the results of intercalibration
  of the SUMER (Solar Ultraviolet Measurements of Emitted Radiation)
  spectrometer (detectors A and B) and the GIS (Grazing Incidence
  Spectrometer), one of two spectrometers that compose the CDS (Coronal
  Diagnostic Spectrometer) on the Solar and Heliospheric Observatory
  (SOHO). The two instruments observed simultaneously radiances of
  emission lines at or near the center of the solar disk. The emission
  line chosen for intercomparison was Ne viii at 770 Å. However,
  such an intercomparison of the SUMER and CDS-GIS measurements means
  comparing two data sets with large differences in resolution and field
  of view. The latter difference, especially, introduces differences
  in the measured intensities caused by the solar variability that is
  relatively strong in the 770- Å line. Using a statistical approach to
  overcome this problem, we found that the ratio of the GIS to the SUMER
  average radiances amounted to 2.6 +/- 0.9 before the SOHO ’s loss of
  attitude and to 2.1 +/- 0.7 afterward. These findings confirm earlier
  estimates of the GIS ’s responsivity being too low, and an update
  of the GIS calibration is recommended. Despite the large differences
  in resolution and field of view of the two instruments, the shapes of
  their normalized and rescaled histograms of the radiances agree well
  and therefore represent characteristic features of the Ne viii line.

Title: New UV detectors for solar observations
Authors: Hochedez, Jean-Francois E.; Schuehle, Udo H.; Pau, Jose L.;
   Alvarez, Jose; Hainaut, Olivier; Appourchaux, Thierry P.; Auret, F. D.;
   Belsky, Andrei; Bergonzo, Philippe; Castex, M. C.; Deneuville, A.;
   Dhez, Pierre; Fleck, Bernhard; Haenen, Ken; Idir, Mourad; Kleider,
   Jean Paul; Lefeuvre, Elie; Lemaire, Philippe; Monroy, E.; Muret, P.;
   Munoz, Elias; Nesladek, Milos; Omnes, Franck; Pace, Emanuele; Peacock,
   Anthony J.; Van Hoof, Chris A.
Bibcode: 2003SPIE.4853..419H
Altcode:
  BOLD (Blind to the Optical Light Detectors) is an international
  initiative dedicated to the development of novel imaging detectors
  for UV solar observations. It relies on the properties of wide bandgap
  materials (in particular diamond and Al-Ga-nitrides). The investigation
  is proposed in view of the Solar Orbiter (S.O.) UV instruments, for
  which the expected benefits of the new sensors -primarily visible
  blindness and radiation hardness- will be highly valuable. Despite
  various advances in the technology of imaging detectors over the last
  decades, the present UV imagers based on silicon CCDs or microchannel
  plates exhibit limitations inherent to their actual material
  and technology. Yet, the utmost spatial resolution, fast temporal
  cadence, sensitivity, and photometric accuracy will be decisive for
  the forthcoming solar space missions. The advent of imagers based on
  wide-bandgap materials will permit new observations and, by simplifying
  their design, cheaper instruments. As for the Solar Orbiter, the
  aspiration for wide-bandgap material (WBGM) based UV detectors is still
  more sensible because the spacecraft will approach the Sun where the
  heat and the radiation fluxes are high. We describe the motivations,
  and present the program to achieve revolutionary flight cameras within
  the Solar Orbiter schedule as well as relevant UV measurements.

Title: Quiet-Sun chromospheric network evolution
Authors: Lemaire, Philippe; Vial, J. -C.; Curdt, W.; Schühle, U.;
   Wilhelm, K.
Bibcode: 2002ESASP.505..477L
Altcode: 2002solm.conf..477L; 2002IAUCo.188..477L
  Using the SUMER/SOHO spectrometer we have observed the same quiet-Sun
  area during several days in a set of eight spectral lines of the
  transition region. Line intensity maps of the rastered areas are used to
  separate the interior of the supergranular cells from the network. Then,
  following the evolution of the supergranular pattern, we measure the
  variations of intensity and the Doppler shifts at several temperatures
  of formation of the transition region. We find that the overall flow
  velocity of the cell interior and the network generally decays within
  ten hours, which represents a significant part of the supergranular
  lifetime.

Title: Preface (SOLMAG 2002)
Authors: Tsiropoula, Georgia; Schühle, Udo
Bibcode: 2002ESASP.505D..13T
Altcode: 2002IAUCo.188D..13T; 2002solm.confD..13T
  No abstract at ADS

Title: Intercalibration of CDS and SUMER
Authors: Pauluhn, A.; Lang, J.; Schühle, U.; Solanki, S. K.; Wilhelm,
   K.; Pike, C. D.; Thompson, W. T.; Rüedi, I.; Hollandt, J.; Huber,
   M. C. E.
Bibcode: 2002ESASP.508..223P
Altcode: 2002soho...11..223P
  The outcome of the Joint Observing Programme (JOP) Intercal-01, which
  is the intercalibration of the SUMER (Solar Ultraviolet Measurements
  of Emitted Radiation) instrument (detectors A and B) and the two CDS
  (Coronal Diagnostic Spectrometer) instruments, the Normal Incidence
  Spectrometer (NIS) and the Grazing Incidence Spectrometer (GIS),
  is presented. Recent calibration updates of both instruments have
  been employed, and the results indicate a very good correlation and
  agreement of the measured radiances within the individual uncertainties.

Title: Variation of the full Sun hydrogen Lyman α and β profiles
    with the activity cycle
Authors: Lemaire, Philippe; Emerich, C.; Vial, J. -C.; Curdt, W.;
   Schühle, U.; Wilhelm, K.
Bibcode: 2002ESASP.508..219L
Altcode: 2002soho...11..219L
  Full Sun hydrogen Lyman α and β profiles obtained through the
  activity cycle are needed to compare with stars, to understand the
  hydrogen distribution in the heliosphere and to evaluate the processes
  in the upper planetary atmospheres. Using the SUMER/SOHO telesocope
  scattered light properties, we have measured the Lyman α and β
  profiles at different epochs of the solar activity cycle. Here we
  report modifications in the intensity and the shape of the profiles.

Title: Transition region quiet sun velocity field evolution
Authors: Lemaire, P.; Artzner, G.; Vial, J. -C.; Curdt, W.; Schühle,
   U.; Wilhelm, K.
Bibcode: 2002AdSpR..30..487L
Altcode:
  The UV/EUV SUMER spectrometer aboard SOHO can record profiles of lines
  emitted by elements at different stages of ionization corresponding
  to several temperatures within the transition region temperature
  range. During the solar cycle minimum in July 1996, we were able to
  observe the quiet Sun during five consecutive days. From the line
  positions we have determined the velocity fields and follow their time
  variations at different temperatures in the transition region. The line
  intensity maps are used to separate supergranular cells and network and
  they allow to compare the behaviors of the velocity fields evolution in
  the two structures. The results are critically analyzed and discussed.

Title: Solar Vacuum-ultraviolet Radiometry with SUMER
Authors: Wilhelm, K.; Schuhle, U.; Curdt, W.; Dammasch, I. E.;
   Hollandt, J.; Lemaire, P.; Huber, M. C. E.
Bibcode: 2002ISSIR...2..145W
Altcode: 2002ESASR...2..145W; 2002rcs..conf..145W
  Since the beginning of 1996, the space-based telescope and
  spectrograph SUMER (Solar Ultraviolet Measurements of Emitted
  Radiation) on the SOlar and Heliospheric Observatory (SOHO) of ESA
  and NASA has obtained spectra of many features of the quiescent and
  active Sun with high spectral and spatial resolution. In addition,
  irradiance and radiance measurements of line and continuum emission
  have been performed in the wavelength range 46.5 nm to 161.0 nm. The
  instrument was radiometrically calibrated against the Berlin Electron
  Storage ring for SYnchrotron radiation (BESSY I), a primary source
  standard, with the help of a transfer source standard based on a
  hollow-cathode discharge lamp. A thorough cleanliness programme,
  specifically aimed at chemical contamination control, resulted in an
  excellent radiometric stability of the normal-incidence optical system
  as well as of the detectors. This has been verified under operational
  conditions by various techniques employed during the SOHO mission,
  such as line-ratio studies, observations of stars, and comparisons with
  other instruments. The observations provide vacuum-ultraviolet (VUV)
  radiometry of the Sun in many emission lines and continua of atoms
  and ions with relative standard uncertainties of 15 % (detector A)
  and 20 % (detector B) for the wavelength range 53 nm to 124 nm, with
  larger uncertainties outside this interval and after the SOHO recovery
  in 1998. We report on the present state of the SUMER radiometric
  calibration and provide a full bibliography related to this topic.

Title: The Solar Orbiter Mission and Design Recommendations
Authors: Schuhle, U.; Thomas, R.; Hochedez, J. -F.
Bibcode: 2002ISSIR...2..361S
Altcode: 2002ESASR...2..361S; 2002rcs..conf..361S
  A short overview is given of the Solar Orbiter mission. First, the key
  scientific aims of the mission are briefly described. As the mission
  profile has consequences on the design of the payload instruments
  and their calibration, the mission design is described. Possible
  implications and problems for the cleanliness and the calibration
  stability of the instruments are outlined. Some solutions are discussed.

Title: Intercalibration of CDS and SUMER
Authors: Pauluhn, A.; Lang, J.; Schuhle, U.; Solanki, S. K.; Wilhelm,
   K.; Thompson, W. T.; Pike, C. D.; Ruedi, I.; Hollandt, J.; Huber,
   M. C. E.
Bibcode: 2002ISSIR...2..235P
Altcode: 2002rcs..conf..235P; 2002ESASR...2..235P
  Simultaneous observations of the same solar features with different
  instruments provide a way to compare radiometric calibrations and
  detect changes in responsivity with time of EUV instruments in space
  within the combined uncertainties of the individual instruments. Here
  we present the intercalibration of the SUMER (Solar Ultraviolet
  Measurements of Emitted Radiation) instrument (detectors A and B) and
  the two CDS (Coronal Diagnostic Spectrometer) instruments, the Normal
  Incidence Spectrometer (NIS) and the Grazing Incidence Spectrometer
  (GIS) on the Solar and Heliospheric Observatory (SOHO). This work
  describes the results of the Joint Observing Programme Intercal 01
  and presents quiet-Sun comparisons from March 1996 up to February
  2001, which represents the complete set of all available Intercal
  01 measurements. Recent calibration updates of both instruments are
  employed, and the results indicate a very good correlation and agreement
  of the measured radiances within the combined uncertainties.

Title: Properties of ultraviolet lines observed with the Coronal
    Diagnostic Spectrometer (CDS/SOHO) in coronal holes and the quiet Sun
Authors: Stucki, K.; Solanki, S. K.; Pike, C. D.; Schühle, U.;
   Rüedi, I.; Pauluhn, A.; Brković, A.
Bibcode: 2002A&A...381..653S
Altcode:
  We present an analysis of 14 ultraviolet emission lines belonging to
  different atoms and ions observed inside polar coronal holes and in
  the normal quiet Sun. The observations were made with the Coronal
  Diagnostic Spectrometer (CDS) onboard the Solar and Heliospheric
  Observatory (SOHO). This study extends previous investigations made
  with the Solar Ultraviolet Measurements of Emitted Radiation (SUMER)
  spectrometer to higher temperatures. We compare line intensities,
  shifts and widths in coronal holes with the corresponding values
  obtained in the quiet Sun. While all lines formed at temperatures above
  7 x 10<SUP>5</SUP> K show clearly the presence of the hole in their
  intensities, differences in line width are more subtle, with cooler
  lines being broader in coronal holes, while hotter lines tend to be
  narrower. According to the present data all lines are blueshifted inside
  the coronal hole compared to the normal quiet Sun. Almost all the lines
  formed between 80 000 K and 600 000 K (i.e. transition-region lines)
  show a correlation between blueshifts and brightness within coronal
  holes. This is in agreement with the conclusion reached by Hassler et
  al. (\cite{Hassler1999}) that the fast solar wind emanates from the
  network and supports our previous study (Stucki et al. 2000b). For
  coronal lines, this trend seems to be reversed.

Title: New UV Detector Concepts
Authors: Hochedez, J. -F.; Schuhle, U.; Lemaire, P.
Bibcode: 2002ISSIR...2..371H
Altcode: 2002rcs..conf..371H; 2002ESASR...2..371H
  BOLD (Blind to the Optical Light Detectors) is an international
  initiative dedicated to the development of novel imaging detectors
  for UV solar observations. It relies on the properties of wide-bandgap
  semiconductor materials (in particular diamond and Al-Ganitrides). This
  investigation is proposed in view of the Solar Orbiter UV instruments,
  for which the expected benefits of the new sensors, visible blindness
  and radiation hardness, will be highly valuable. Despite various
  advances in the technology of imaging detectors over the last few
  decades, the present UV imagers based on silicon CCDs or microchannel
  plates exhibit limitations which are inherent to their actual material
  and technology. Yet the utmost spatial resolution, fast temporal
  cadence, sensitivity, and photometric accuracy will all be decisive for
  forthcoming solar space missions. The advent of imagers made of large
  wide-bandgap semiconductors would surmount many present weaknesses. This
  would open up new scientific prospects and, by simplifying their design,
  would even make the instruments cheaper. As for the Solar Orbiter,
  the aspiration for wide-bandgap semiconductor-based UV detectors is
  still more desirable because the spacecraft will approach the Sun
  where heat and radiation fluxes are high. We describe the motivations
  leading to such new developments, and present a programme to achieve
  revolutionary flight cameras within the Solar Orbiter schedule.

Title: Intercalibration of SUMER and CDS on SOHO. II. SUMER detectors
    A and B and CDS NIS
Authors: Pauluhn, Anuschka; Rüedi, Isabelle; Solanki, Sami K.;
   Schühle, Udo; Wilhelm, Klaus; Lang, Jim; Thompson, William T.;
   Hollandt, Jörg
Bibcode: 2001ApOpt..40.6292P
Altcode:
  Results of an intercalibration between the extreme-ultraviolet
  spectrometers Coronal Diagnostic Spectrometer (CDS) and Solar
  Ultraviolet Measurements of Emitted Radiation (SUMER) on board the Solar
  and Heliospheric Observatory (SOHO) are reported. The results of the
  joint observing program Intercal_01 are described, and intercalibration
  results up to July 2000 of both SUMER detectors A and B and of the
  CDS Normal Incidence Spectrometer (NIS) are presented. The instruments
  simultaneously observed radiance of emission lines at the center of the
  Sun, and three lines have been chosen for intercomparison: He I 584 Å,
  Mg X 609 Å, and Mg X 624 Å. Initially the same area was observed by
  both instruments, but, after restrictions were imposed by the scanning
  mechanism of SUMER in November 1996, the instruments viewed areas of
  different sizes. Nevertheless, the temporal correlation between the
  two instruments remained good through June 1998, when contact with
  the SOHO spacecraft was lost. Until then the CDS instrument measured
  (33+/-5)% and (38+/-7)% (+/-1σ) higher intensity than SUMER in the
  Hz I 584-Å line on average for detectors A and B, respectively. Data
  from SUMER detector B agreed well for Mg X 609 Å and Mg X 624 Å
  with the CDS intensities, showing offsets of (2+/-10)% and (9+/-15)%,
  much less than the data of detector A with offsets of (7+/-8)% and
  (16+/-7)% for the two lines, respectively, relative to CDS. Finally,
  the intercalibration measurements after the loss and recovery of the
  SOHO spacecraft are analyzed. The data for observations from November
  1998 to July 2000 are compared, and it is shown that, although the
  responses of the instruments have changed, the CDS and the SUMER still
  perform well, and their temporal correlation is good.

Title: The SUMER spectral atlas of solar-disk features
Authors: Curdt, W.; Brekke, P.; Feldman, U.; Wilhelm, K.; Dwivedi,
   B. N.; Schühle, U.; Lemaire, P.
Bibcode: 2001AIPC..598...45C
Altcode: 2001sgc..conf...45C
  A far-ultraviolet and extreme-ultraviolet (FUV, EUV) spectral atlas
  of the Sun between 670 Å and 1609 Å in first order of diffraction
  has been derived from observations obtained with the SUMER (Solar
  Ultraviolet Measurements of Emitted Radiation) spectrograph on
  the spacecraft SOHO (Solar and Heliospheric Observatory) [1]. The
  atlas contains spectra of the average quiet Sun, a coronal hole and
  a sunspot on disk. Different physical parameters prevalent in the
  bright network (BN) and in the cell interior (CI)-contributing in a
  distinct manner to the average quiet-Sun emission-have their imprint
  on the BN/CI ratio, which is also shown for the entire spectral
  range. With a few exceptions, all major lines are given with their
  identifications and wavelengths. Lines that appear in second order
  are superimposed on the first order spectra, but below 500 Å the
  responsivity of the normal-incidence optical system is very low. The
  spectra include emissions from atoms and ions in the temperature range
  6 10<SUP>3</SUP> K to 2 10<SUP>6</SUP> K, i.e., continua and mission
  lines emitted from the lower chromosphere to the corona. This spectral
  atlas, with its broad wavelength coverage, provides a rich source
  of new diagnostic tools for studying the physical parameters in the
  chromosphere, the transition region and the corona. In particular,
  the wavelength range below 1100 Å as observed by SUMER represents
  a significant improvement over the spectra produced in the past. In
  view of the manifold appearance and temporal variation of the solar
  atmosphere it is obvious that our atlas can only be a-hopefully
  typical-snapshot. The spectral radiances are determined with a
  relative uncertainty of 0.15 to 0.30 (1σ), and the wavelength scale
  is accurate to typically 10 mÅ, which is the level achievable with
  semi-automatic processing. The SUMER solar-disk spectral atlas will
  be published in the near future by Curdt et al. [2]. It includes
  profiles of the average quiet Sun, an equatorial coronal hole, and
  a sunspot. As an example we show in Fig. 1 the spectral range from
  1300 Å to 1342 Å with the prominent O I and C II lines. Resolved
  emission lines are indicated by a mark, the measured wavelength in
  angstrom, and the identification, if available. Marks point to line
  lists available in the literature, where additional information about
  a specific line can be found [3-7]. New lines or identifications
  are indicated. Lines observed in first order and in second-order of
  diffraction are distinguished. Only the three least-significant digits
  of the wavelength values are given. If available, unidentified lines
  are characterized by the temperature classification defined in [3] (a:
  T<SUB>e</SUB>&lt;3 10<SUP>5</SUP> b: T<SUB>e</SUB>~3 10<SUP>5</SUP> c:
  T<SUB>e</SUB>~4 10<SUP>5</SUP> d: 6 10<SUP>5</SUP>&lt;T<SUB>e</SUB>
  &lt;9 10<SUP>5</SUP> e: T<SUB>e</SUB>~1.4 10<SUP>6</SUP> f:
  T<SUB>e</SUB>~1.8 10<SUP>6</SUP>). The vertical axes are scaled
  to spectral radiance in units of mW sr<SUP>-1</SUP> m<SUP>-2</SUP>
  Å<SUP>-1</SUP> on the left the radiometric calibration for first
  order lines is given, on the right for second order lines. Note,
  that second order lines are always superimposed on a first order
  background. We have taken care of the type of photocathode (bare or KBr)
  when applying the radiometric calibration to different sections of the
  spectrum. Also displayed in green is the BN/CI ratio in an attempt
  to characterize the quiet-Sun chromospheric network structure. A
  pre-print of the SUMER spectral atlas and a line list is available at
  http://www.linmpi.mpg.de/~curdt. .

Title: Wide bandgap EUV and VUV imagers for the Solar Orbiter
Authors: Hochedez, Jean-François; Lemaire, Philippe; Pace, Emanuele;
   Schühle, Udo; Verwichte, Erwin
Bibcode: 2001ESASP.493..245H
Altcode: 2001sefs.work..245H
  No abstract at ADS

Title: The SUMER spectral atlas of solar-disk features
Authors: Curdt, W.; Brekke, P.; Feldman, U.; Wilhelm, K.; Dwivedi,
   B. N.; Schühle, U.; Lemaire, P.
Bibcode: 2001A&A...375..591C
Altcode:
  A far-ultraviolet and extreme-ultraviolet (FUV, EUV) spectral atlas of
  the Sun between 670 Å and 1609 Å in the first order of diffraction
  has been derived from observations obtained with the SUMER (Solar
  Ultraviolet Measurements of Emitted Radiation) spectrograph on the
  spacecraft SOHO (Solar and Heliospheric Observatory). The atlas contains
  spectra of the average quiet Sun, a coronal hole and a sunspot on the
  disk. Different physical parameters prevalent in the bright network (BN)
  and in the cell interior (CI) - contributing in a distinct manner to
  the average quiet-Sun emission - have their imprint on the BN/CI ratio,
  which is also shown for almost the entire spectral range. With a few
  exceptions, all major lines are given with their identifications and
  wavelengths. Lines that appear in second order are superimposed on the
  first order spectra. These lines are clearly marked in the atlas. The
  spectra include emissions from atoms and ions in the temperature range
  6*E<SUP>3</SUP> K to 2*E<SUP>6</SUP> K, i.e., continua and emission
  lines emitted from the lower chromosphere to the corona. This spectral
  atlas, with its broad wavelength coverage, provides a rich source of new
  diagnostic tools to study the physical parameters in the chromosphere,
  the transition region and the corona. In particular, the wavelength
  range below 1100 Å as observed by SUMER represents a significant
  improvement over the spectra produced in the past. In view of the
  manifold appearance and temporal variation of the solar atmosphere,
  it is obvious that our atlas can only be a - hopefully typical -
  snapshot. Brief descriptions of the data reduction and calibration
  procedures are given. The spectral radiances are determined with a
  relative uncertainty of 0.15 to 0.30 (1sigma ) and the wavelength
  scale is accurate to typically 10 mÅ. The atlas is also available
  in a machine readable form. Table A.1 is only available in electronic
  form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5)
  or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/375/591

Title: VizieR Online Data Catalog: SUMER Spectral Atlas of Solar
    Disk Features (Curdt+, 2001)
Authors: Curdt, W.; Brekke, P.; Feldman, U.; Wilhelm, K.; Dwivedi,
   B. N.; Schuhle, U.; Lemaire, P.
Bibcode: 2001yCat..33750591C
Altcode:
  List of spectral lines in the wavelength range from 668Å to 1611Å
  identified in SUMER (Solar Ultraviolet Measurements of Emitted
  Radiation, spectrograph on the spacecraft SOHO) spectra of the average
  quiet Sun (QS), a coronal hole (CH) and a sunspot on disk (SS). Spectral
  lines observed in second order of diffraction which are also given
  here, extend the lower wavelength limit to below 500Å. For each entry
  we give the observed wavelengths in angstrom, the identification,
  the transition, the peak of spectral radiance, L<SUP>peak</SUP>, in
  mW/(sr*m<SUP>2</SUP>*Å) (incl. background), and a cross-reference
  to other line lists available in the literature (cf., Sect. 5.1). For
  second-order lines radiance entries are generally not provided, since
  the background separation in both orders of diffraction is a non-trivial
  task, which can not be automated. Only a few radiance values of strong
  second-order lines with negligible first-order contribution are given,
  which are marked by an asterisk (*). (1 data file).

Title: Chromospheric Dynamics as can be Inferred from SUMER/SOHO
    Observations
Authors: Rybák, J.; Kučera, A.; Curdt, W.; Schühle, U.; Wöhl, H.
Bibcode: 2001ASSL..259..247R
Altcode: 2001dysu.conf..247R
  Experience with the SUMER/SOHO observations of the chromospheric
  dynamics and the reduction of the acquired data is summarized on
  base of the SOHO Joint Operation Program 78 which is focused on the
  variability of the chromosphere and the transition region to the corona.

Title: Comparison of quiet-Sun radiances measured by CDS and SUMER
    on SOHO
Authors: Pauluhn, A.; Solanki, S. K.; Schühle, U.; Wilhelm, K.;
   Lang, J.; Thompson, W. T.; Rüedi, I.; Hollandt, J.; Huber, M. C. E.
Bibcode: 2001SSRv...97...63P
Altcode:
  Since the beginning of the SOHO (Solar and Heliospheric Observatory)
  mission an intercalibration programme was carried out which included
  simultaneous observations of the EUV instruments CDS (Coronal Diagnostic
  Spectrometer) and SUMER (Solar Ultraviolet Measurements of Emitted
  Radiation) of common targets on the quiet Sun. The observations in the
  chromospheric line of He i (584 Å) and the two coronal lines of Mg x
  (609 Å and 624 Å) thus cover the long period of 4 years and provide a
  data set highly suitable not only for instrumental comparison but also
  for studies of the quiet Sun's long term variability. Up to the SOHO
  accident, both instruments show a very good temporal correlation and
  stability. Even after the loss and recovery of the spacecraft, when
  the instruments had been exposed to extreme temperature conditions,
  the performance of the CDS and SUMER instruments is still good, as is
  the temporal correlation. However, the ratio between the efficiencies
  of the two instruments, which remained constant with time until the
  SOHO accident seems to have changed afterwards. In the coronal lines
  both instruments show an increase of average radiances towards the
  solar maximum.

Title: Statistical Features of the Quiet Sun in EUV
Authors: Pauluhn, A.; Solanki, S. K.; Rüedi, I.; Landi, E.;
   Schühle, U.
Bibcode: 2001IAUS..203..416P
Altcode:
  The frequency distribution of the extreme ultraviolet (EUV) intensities
  in the quiet Sun has in the past usually been modelled using two
  Gaussians. Here we test this and other distribution functions against
  observed distributions with exceptional statistics. The data were
  obtained in a number of spectral lines observed with two extreme
  ultraviolet spectrometers, CDS (Coronal Diagnostic Spectrometer)
  and SUMER (Solar Ultraviolet Measurements of Emitted Radiation) on
  board the Solar and Heliospheric Observatory (SOHO). We show that the
  frequency distribution of the radiance is best modelled by a lognormal
  distribution or by a sum of a lognormal and a Gaussian. The fact that
  the radiance distribution of the quiet Sun including the network and
  the intranetwork is better reproduced by a single lognormal distribution
  function than by two Gaussians suggests that the same heating processes
  are acting in both types of features. The shape of the distribution
  function shows a clear temperature dependence.

Title: Properties of Solar Polar Coronal Hole Plasmas Observed above
    the Limb
Authors: Doschek, G. A.; Feldman, U.; Laming, J. M.; Schühle, U.;
   Wilhelm, K.
Bibcode: 2001ApJ...546..559D
Altcode:
  We determine the line-of-sight emission measure distribution and
  nonthermal motions as a function of height above the limb in the
  north and south polar coronal holes. These quantities are derived from
  extreme-ultraviolet (EUV) spectra obtained from the Solar Ultraviolet
  Measurements of Emitted Radiation (SUMER) spectrometer on the Solar
  and Heliospheric Observatory (SOHO) spacecraft. The SUMER slit was
  oriented along the north-south direction for all the observations,
  and the spatial resolution is about 1". The spectra were obtained
  from a number of different types of observations in 1996. We select
  a group of emission lines for analysis for which, under the usual
  assumption of ionization equilibrium, the maximum emissivities span
  the temperature range from about 3×10<SUP>5</SUP> K up to about
  1.1×10<SUP>6</SUP> K. We compare our results with recently published
  similar observations of a west limb quiet-Sun streamer region, with
  other coronal hole results based on SUMER spectra, and with earlier
  observations of the quiet Sun and coronal holes obtained from Skylab
  and rocket spectra. We find that the electron temperature in the polar
  holes increases with height above the limb, that the emission measure
  distribution of plasma located at line-of-sight heights less than
  about 60" peaks at a temperature of about 9×10<SUP>5</SUP> K, and that
  nonthermal motions sometimes, but not always, increase slightly with
  height above the limb. When observed, these increases level off above
  the limb at about 120". We speculate that the increases with height
  above the limb may be a manifestation of the fast solar wind. They
  may also be due to the reduction in transition region structures with
  increasing limb height. We also discuss wave heating as a cause of
  the line width increases.

Title: Radiance of Solar Spectral Lines observed with CDS and SUMER
on SOHO (CD-ROM Directory: contribs/pauluhn)
Authors: Pauluhn, A.; Schühle, U.; Solanki, S. K.; Rüedi, I.; Lang,
   J.; Pike, C. D.; Thompson, W. T.; Huber, M. C. E.
Bibcode: 2001ASPC..223..721P
Altcode: 2001csss...11..721P
  No abstract at ADS

Title: Comparison of far-ultraviolet emission lines formed in coronal
    holes and the quiet Sun
Authors: Stucki, K.; Solanki, S. K.; Schühle, U.; Rüedi, I.; Wilhelm,
   K.; Stenflo, J. O.; Brković, A.; Huber, M. C. E.
Bibcode: 2000A&A...363.1145S
Altcode:
  We present an analysis of 26 far-ultraviolet emission lines belonging
  to 19 atoms and ions observed on both sides of the boundary of polar
  coronal holes as well as other quiet Sun areas along the limb. The
  observations were made with the SUMER instrument (Solar Ultraviolet
  Measurements of Emitted Radiation) onboard the Solar and Heliospheric
  Observatory (SOHO). We compare line intensities, shifts and widths
  in coronal holes with the corresponding values obtained in the quiet
  Sun. We find that with increasing formation temperature, spectral
  lines show on average an increasingly stronger blueshift in coronal
  holes relative to the quiet Sun at equal heliospheric angle, with the
  coolest lines in our sample (formation temperature ~ 10<SUP>4</SUP>
  K) indicating a small relative redshift. With respect to the rest
  wavelength, however, only lines formed above 5 * 10<SUP>5</SUP> K
  show blueshifts in coronal holes, which is not very different from
  the quiet Sun. The width of the lines is generally larger (by a few
  kilometers per second) inside the coronal hole. Intensity measurements
  clearly show the presence of the coronal hole in Ne VIII lines as well
  as in Fe XII, and provide evidence for a slightly enhanced emission
  in polar coronal holes for lines formed below 10<SUP>5</SUP> K. This
  last result is, however, less certain than the rest due to relatively
  poor statistics. Intensity histograms also exhibit distinct differences
  between coronal hole and quiet-Sun data. For cooler chromospheric lines,
  such as Ni II, the coronal holes display a greater spread in intensities
  than the quiet Sun. Transition-region lines, e.g. O IV, do not reveal
  such differences, while Ne VIII shows characteristics of a coronal line
  with lower average intensity and lower intensity spread inside holes.

Title: Statistics of quiet Sun extreme ultraviolet intensities
Authors: Pauluhn, A.; Solanki, S. K.; Rüedi, I.; Landi, E.;
   Schühle, U.
Bibcode: 2000A&A...362..737P
Altcode:
  The frequency distribution of the extreme ultraviolet (EUV) emission
  line intensities in the quiet Sun has in the past often been modelled
  using two Gaussians. This gives adequate fits to observed distributions
  of average statistical significance. In this paper we test this
  and other distribution functions against observed distributions with
  exceptional statistical significance. The data were obtained in a number
  of spectral lines observed with two extreme ultraviolet spectrometers
  on board the Solar and Heliospheric Observatory (SOHO). In this way,
  the influence of spatial resolution and other instrument-specific
  parameters can be identified. The observations span a period of
  more than two years and provide a very large data set of radiance
  measurements of the quiet Sun at or near solar disk centre. We show
  that the frequency distribution of the radiance is best modelled by
  a lognormal distribution. The fact that the radiance distribution of
  the quiet Sun including the network and the intranetwork is better
  reproduced by a single lognormal distribution function than by two
  Gaussians suggests that the same heating processes are acting in both
  types of features. The parameters of the lognormal fit show a clear
  temperature dependence, with the transition region lines exhibiting the
  largest skewness of the distribution and the chromospheric intensity
  distributions being the most symmetric.

Title: On the relationship between shift and intensity of ultraviolet
    lines in coronal holes and the quiet Sun
Authors: Stucki, K.; Solanki, S. K.; Schühle, U.; Rüedi, I.
Bibcode: 2000A&A...362L..49S
Altcode:
  We study the relationship between wavelength shifts and intensities
  of chromospheric, transition-region and coronal ultraviolet emission
  lines in polar coronal holes and in the normal quiet Sun using SUMER
  data. Within coronal holes almost all the lines showing the network
  and formed above 30 000 K show a correlation between blueshifts
  and brightness. This extends and supports the conclusion reached
  by Hassler et al. (1999) that the fast solar wind emanates from the
  network. In the normal quiet Sun, however, we find that only lines
  formed above 2-3 * 10<SUP>5</SUP> K show such a trend, the cooler
  lines being more redshifted in the network. This suggests that either
  there is a fundamental difference in the initial acceleration of
  the solar wind in coronal holes and the normal quiet Sun, or that
  the wavelength-shift versus brightness relationship in the quiet Sun
  stems from other processes or structures (loops) than in coronal holes
  (open field lines).

Title: Radiance variations of the quiet Sun at far-ultraviolet
    wavelengths
Authors: Schühle, U.; Wilhelm, K.; Hollandt, J.; Lemaire, P.;
   Pauluhn, A.
Bibcode: 2000A&A...354L..71S
Altcode:
  We have measured the radiance of quiet-Sun areas at the centre of the
  solar disk using the vacuum-ultraviolet telescope-spectrograph SUMER
  (Solar Ultraviolet Measurements of Emitted Radiation) on the Solar and
  Heliospheric Observatory (SOHO). The radiances of selected emission
  lines have been measured from March 1996 to the present. The lines that
  have been observed regularly since the beginning of the SOHO mission
  are He i 584 Å, Mg x 609 Å and 624 Å, Ne viii 770 Å, N v 1238 Å,
  and the H i Lyman continuum at 880 Å. We investigate the variability
  of these emission lines during the solar minimum and the ascending
  phase of the present solar activity cycle. The transition region and
  coronal lines show an increasing trend of up to 100% since the sunspot
  minimum. The results are important for models of solar VUV variability
  on the basis of radiance contrast ratios of solar disk regions. Our
  spatially resolved images allow a separation of the network and cell
  areas of the quiet-Sun. Both regimes show similar variations.

Title: Mid-term Radiance Variation of Far-Ultraviolet Emission Lines
    from Quiet-Sun Areas
Authors: Schühle, U.; Hollandt, Jorg; Pauluhn, Anuschka; Wilhelm,
   Klaus
Bibcode: 2000ESASP.463..427S
Altcode: 2000sctc.proc..427S
  No abstract at ADS

Title: Solar Irradiances of Ultraviolet Emission Lines Measured
    During the Minimum of Sunspot Activity in 1996 and 1997
Authors: Wilhelm, K.; Lemaire, P.; Dammasch, I. E.; Hollandt, J.;
   Schuhle, U.; Curdt, W.; Kucera, T.; Hassler, D. M.; Humbler, M. C. E.
Bibcode: 2000PCEC...25..389W
Altcode:
  No abstract at ADS

Title: Radiometric Calibration of the Vacuum-Ultraviolet Spectrograph
    SUMER on the SOHO Spacecraft with the B Detector
Authors: Schühle, Udo; Curdt, Werner; Hollandt, Jörg; Feldman, Uri;
   Lemaire, Philippe; Wilhelm, Klaus
Bibcode: 2000ApOpt..39..418S
Altcode:
  The Solar Ultraviolet Measurement of Emitted Radiation (SUMER)
  vacuum-ultraviolet spectrograph was calibrated in the laboratory
  before the integration of the instrument on the Solar and Heliospheric
  Observatory (SOHO) spacecraft in 1995. During the scientific operation
  of the SOHO it has been possible to track the radiometric calibration
  of the SUMER spectrograph since March 1996 by a strategy that employs
  various methods to update the calibration status and improve the
  coverage of the spectral calibration curve. The results for the A
  Detector were published previously Appl. Opt. 36, 6416 (1997) . During
  three years of operation in space, the B detector was used for two
  and one-half years. We describe the characteristics of the B detector
  and present results of the tracking and refinement of the spectral
  calibration curves with it. Observations of the spectra of the stars and
  Leonis permit an extrapolation of the calibration curves in the range
  from 125 to 149.0 nm. Using a solar coronal spectrum observed above
  the solar disk, we can extrapolate the calibration curves by measuring
  emission line pairs with well-known intensity ratios. The sensitivity
  ratio of the two photocathode areas can be obtained by registration of
  many emission lines in the entire spectral range on both KBr-coated and
  bare parts of the detector s active surface. The results are found to be
  consistent with the published calibration performed in the laboratory
  in the wavelength range from 53 to 124 nm. We can extrapolate the
  calibration outside this range to 147 nm with a relative uncertainty
  of 30% (1 ) for wavelengths longer than 125 nm and to 46.5 nm with 50%
  uncertainty for the short-wavelength range below 53 nm.

Title: Comparison of Transient Network Brightenings and Explosive
    Events in the Solar Transition Region
Authors: Chae, Jongchul; Wang, Haimin; Goode, Philip R.; Fludra,
   Andrzej; Schühle, Udo
Bibcode: 2000ApJ...528L.119C
Altcode:
  The relation between transient network brightenings, known as blinkers,
  and explosive events is examined based on coordinated quiet Sun
  observations in the transition region line O V λ630 recorded by
  the Coronal Diagnostic Spectrometer (CDS), in the transition region
  line Si IV λ1402 recorded by the Solar Ultraviolet Measurements of
  Emitted Radiation (SUMER) instrument, and in photospheric magnetograms
  taken by the Big Bear Solar Observatory videomagnetograph. From these
  observations, we find that (1) explosive events, which are traditionally
  defined as features with very broad UV line profiles, tend to keep
  away from the centers of network brightenings and are mostly located
  at the edges of such brightenings, (2) CDS blinkers consist of many
  small-scale, short-lived SUMER ``unit brightening events'' with a
  size of a few arcseconds and a lifetime of a few minutes, and most
  importantly (3) each SUMER unit brightening event is characterized by
  a UV line profile that is not as broad as those of explosive events,
  but still has significantly enhanced wings. Our results imply that,
  like explosive events, individual unit brightening events involve high
  velocities, and, hence, blinkers may have the same physical origin
  as explosive events. It is likely that transient network brightenings
  and explosive events are both due to magnetic reconnection--but with
  different magnetic geometries.

Title: Radiance Variations of Vacuum-Ultraviolet Emission Lines of
    the Quiet Sun Observed with SUMER on SOHO
Authors: Schuhle, U.; Pauluhn, A.; Hollandt, J.; Lemaire, P.;
   Wilhelm, K.
Bibcode: 2000PCEC...25..429S
Altcode:
  No abstract at ADS

Title: Solar spectroradiometry with the telescope and spectrograph
    SUMER on the Solar and Heliospheric Observatory SOHO
Authors: Wilhelm, K.; Schühle, U.; Curdt, W.; Dammasch, I. E.;
   Hollandt, J.; Lemaire, P.; Huber, M. C. E.
Bibcode: 2000Metro..37..393W
Altcode:
  No abstract at ADS

Title: Dynamics of Chromiospheric and Transition Region Lines Observed
    with SOHO/SUMER and the GCT/Tenerife
Authors: Muglach, K.; Fleck, B.; Schühle, U.; Stolpe, F.; Foing,
   B. H.; Wilhelm, K.
Bibcode: 2000AdSpR..25.1731M
Altcode:
  High-resolution spectroscopic observations of the quiet Sun have been
  carried out in September 1996 at the German Gregory Coudé Telescope
  (GCT) in Tenerife and in May 1997 with the SUMER instrument onboard
  SOHO. Time sequences of spectra in the visible and near infrared
  as well as in the ultraviolet have been taken, covering a range of
  heights from the solar photosphere up into the transition region. In
  this contribution we present the dynamical behaviour observed at the
  various heights in the solar atmosphere

Title: Solar Ultraviolet Irradiance and Radiance Observations by
    SUMER on SOHO
Authors: Dammasch, I. E.; Wilhelm, K.; Curdt, W.; Schühle, U.
Bibcode: 1999ESASP.448.1165D
Altcode: 1999ESPM....9.1165D; 1999mfsp.conf.1165D
  No abstract at ADS

Title: Chromospheric and Transition Region Dynamics - Reasons
    and Consequences of the Long-period Instrumental Periodicities
    of SUMER/SOHO
Authors: Rybák, J.; Curdt, W.; Kucera, A.; Schühle, U.; Wöhl, H.
Bibcode: 1999ESASP.448..361R
Altcode: 1999mfsp.conf..361R; 1999ESPM....9..361R
  No abstract at ADS

Title: The solar ultraviolet spectrum from 1200 Å to 1560 Å:
    a radiometric comparison between SUMER/SOHO and SOLSTICE/UARS
Authors: Wilhelm, K.; Woods, T. N.; Schühle, U.; Curdt, W.; Lemaire,
   P.; Rottman, G. J.
Bibcode: 1999A&A...352..321W
Altcode:
  After short descriptions of the SUMER (Solar Ultraviolet Measurements
  of Emitted Radiation) spectrometer onboard SOHO (the Solar and
  Heliospheric Observatory) and the SOLSTICE (Solar-Stellar Irradiance
  Comparison Experiment) spectrometer on UARS (the Upper Atmosphere
  Research Satellite), a radiometric comparison is carried out of solar
  irradiance spectra measured by SOLSTICE and spectra derived from
  SUMER radiance observations of quiet-Sun regions in the wavelength
  range from 1200 Å to 1560 Å. The emission lines N v (lambda 1238)
  and C iv (lambda 1548) are considered in detail. For these lines,
  irradiance data are also available from full-Sun raster scans of SUMER
  and deviations of less than 15% are found between SOLSTICE and SUMER
  results - well within the combined uncertainty margins.

Title: Relationship between Line Shift and Intensity Inside Coronal
    Holes
Authors: Stucki, K.; Solanki, S. K.; Rüedi, I.; Schüehle, U.
Bibcode: 1999ESASP.446..633S
Altcode: 1999soho....8..633S
  We analyse SUMER spectra of a group of lines belonging to chromospheric,
  transition region and coronal ions obtained on both sides of the
  boundary of polar coronal holes as well as at other locations along the
  limb. We study the relationship between line shifts and intensities in
  coronal holes and compare to values obtained in the quiet Sun. We find
  that within coronal holes, a trend can be detected in some transition
  region lines, like O V and N V, in the sense that the lines are more
  strongly blueshifted in brighter regions. This is in agreement with
  the conclusion reached by Hassler et al. (1999, Science 283, 810-813)
  that the fast solar wind emanates from the network. Furthermore,
  a correlation of line shifts of ions formed at higher temperatures
  (Ne VIII, Fe XII) with intensities of lines showing network structures
  (Si I, N III) is presented.

Title: The SUMER EUV Atlas in the Spectral Range 670 A - 1498 A
Authors: Curdt, W.; Brekke, P.; Schühle, U.; Wilhelm, K.; Dwivedi,
   B. N.
Bibcode: 1999ESASP.446..251C
Altcode: 1999soho....8..251C
  An extreme ultraviolet spectral atlas between 660 and 1600 A (first
  order) of a quiet Sun, a coronal hole, and a Sun spot region has
  been derived from observations with the SUMER (Solar Ultraviolet
  Measurements of Emitted Radiation) instrument on SOHO. More than 1000
  emission lines are given with the best available identification. The
  spectra are radiometrically calibrated. Lines in second order are
  superimposed on this spectrum. The spectral scans include emissions
  from atoms and ions in the temperature range from 6 000 to 2000 000 K,
  i.e., continua and emission lines emitted from the lower chromosphere
  to the corona. This broad wavelength coverage provides an important
  new diagnostic tool for studying the essential physical parameters
  throughout the upper solar atmosphere. In particular, the wavelength
  range shortward of 1100 A as observed by SUMER represents a significant
  improvement over the spectra produced in the past. A brief description
  of the data reduction and calibration procedures is given. The absolute
  intensities are determined with an uncertainty of better than +- 15%
  in most of the range presented, and the wavelength scale is accurate
  to better than 0.01 A. The atlas will also be available in machine
  readable form.

Title: Molecular Hydrogen Lines Observed with SUMER in the Spectrum
    of a Sunspot
Authors: Schüehle, U.; Brown, C. M.; Curdt, W.; Feldman, U.
Bibcode: 1999ESASP.446..617S
Altcode: 1999soho....8..617S
  No abstract at ADS

Title: Chromospheric And Transition Region Dynamics - Reasons
    and Consequences of the Short Period Instrumental Periodicities
    of SOHO/SUMER
Authors: Rybak, Jan; Curdt, Werner; Kučera, Ales; Schüehle, Udo;
   Wöehl, Hubertus
Bibcode: 1999ESASP.446..579R
Altcode: 1999soho....8..579R
  The instrumentally caused oscillations of the spectral lines intensity
  and velocity, determined with the SUMER spectrometer onboard SoHO, are
  presented. On examples of two long-term measurements of O I, C II and O
  VI lines, it is shown that the reason of this instrumental effect was
  the insufficient precision of the solar rotation compensation of the
  spectrometer slit position. In both observational runs the standard
  rotation compensation procedure, performed on-line by the instrument,
  was selected for the long-term observations. The minor periodical
  motion of the slit position on the solar disk was taking place during
  such observations and this effect produced the regular changes of the
  measured line intensities and velocities. The significant enhancements
  of the oscillations amplitudes around the frequency 2.56 mHz and its
  harmonics were detected in the cases of observations, performed at
  the disk center. Unfortunately, these frequencies are just in the
  range of the typical oscillations determined till now in the upper
  solar atmosphere ! Consequences of this instrumental effect for SUMER
  measurements of the chromospheric and transition region dynamics
  are discussed. Procedures how to exclude the effect from the data
  post-facto as well as how to modify the future SUMER oscillations
  measurements in order to avoid the effect are proposed

Title: Coordinated observations between SOHO/SUMER and ground during
the 1998 total eclipse: Non-thermal line broadenings and electron
    densities in a polar coronal hole
Authors: Patsourakos, S.; Vial, J. -C.; Gabryl, J. -R.; Koutchmy,
   S.; Schühle, U.
Bibcode: 1999AIPC..471..285P
Altcode: 1999sowi.conf..285P
  Alfvén waves represent one of the most prominent ways of heating the
  solar corona and accelerating the solar wind. One of their signatures
  is to broaden the spectral lines in excess of their thermal width. Here
  we aim to combine observations of non-thermal broadenings measured
  by SUMER in OVI (1037.6 Å) line and electronic densities derived
  from white-light observations during the 1998 total eclipse. After
  checking the validity of the frequently-used assumption of equal ion
  and electron temperatures, we compute the variation of the non-thermal
  velocity as a function of height in an interplume region within the
  south polar coronal hole.

Title: Properties of Quiet-Sun Coronal Plasmas at Distances of
    1.03&lt;=R<SUB>solar</SUB>&lt;=1.50 along the Solar Equatorial Plane
Authors: Feldman, U.; Doschek, G. A.; Schühle, U.; Wilhelm, K.
Bibcode: 1999ApJ...518..500F
Altcode:
  We determine the physical properties, i.e., electron temperature,
  density, line-of-sight emission measure, and element-abundance variation
  with height, in the Sun's equatorial west limb streamer region from
  extreme-ultraviolet (EUV) spectra recorded by the Solar Ultraviolet
  Measurements of Emitted Radiation (SUMER) spectrometer on the Solar and
  Heliospheric Observatory (SOHO) spacecraft. The spectra were recorded
  on 1996 November 21-22 during a special ``roll'' maneuver in which
  the SUMER slit was oriented in the east-west direction. Because the
  SUMER spectrometer is stigmatic along the slit length, the spectra are
  spatially resolved in the east-west direction. The spectra we discuss
  cover an effective distance range outside the west limb from 1.03 to
  1.50 solar radii (R<SUB>solar</SUB>) the maximum spatial resolution is
  1<SUP>''</SUP>. We select a group of emission lines for analysis that
  under the usual ionization equilibrium assumption span the temperature
  range from 3×10<SUP>5</SUP> up to 2×10<SUP>6</SUP> K. However,
  we note that above the limb a major fraction of a line intensity may
  arise at a temperature that is far from the temperature of maximum
  emitting efficiency in ionization equilibrium. In this paper we assume
  ionization equilibrium in deriving plasma parameters. Readers can redo
  our analysis without this assumption if desired, because the line
  intensities we present in this paper are simply the measured photon
  production rates in the lines. Assuming ionization equilibrium, we
  determine the electron temperature, electron density, line-of-sight
  emission measure, and abundance variation with height above the limb
  from the line intensities and line intensity ratios. The spatial
  resolution has allowed us to detect an apparent element-abundance
  variation as a function of height above the west limb that is strong
  evidence for gravitational settling of ``heavy'' elements.

Title: Coronal Hole Properties Observed with SUMER
Authors: Stucki, K.; Solanki, S. K.; Rüedi, I.; Stenflo, J. O.;
   Brković , A.; Schühle, U.; Wilhelm, K.; Huber, M. C. E.
Bibcode: 1999SSRv...87..315S
Altcode:
  We analyze SUMER spectra of 14 lines belonging to 12 ions, obtained
  on both sides of the boundary of polar coronal holes as well as at
  other locations along the limb. We compare line intensities, shifts
  and widths in coronal holes with values obtained in the quiet Sun. We
  find that with increasing formation temperature, spectral lines show
  an increasingly stronger blueshift in coronal holes relative to the
  quiet Sun at an equal heliospheric angle. The width of the lines is
  generally larger (by a few km/s) inside the coronal hole. Intensity
  measurements show the presence of the coronal hole in Ne VIII lines
  as well as in Fe XII, with evidence for a slightly enhanced emission
  in polar coronal holes for lines formed below 10<SUP>5</SUP> K.

Title: Coronal Holes Versus Normal Quiet Sun Observed with SUMER
Authors: Stucki, K.; Solanki, S. K.; Rüedi, I.; Stenflo, J. O.;
   Brković, A.; Schühle, U.; Wilhelm, K.; Huber, M. C. E.
Bibcode: 1999Ap&SS.264...53S
Altcode: 1998Ap&SS.264...53S
  We present a preliminary analysis of spectral lines obtained with the
  SUMER instrument (Solar Ultraviolet Measurements of Emitted Radiation)
  onboard the Solar and Heliospheric Observatory (SOHO), as observed
  during three observing campaigns. From the 70 observed spectral lines,
  we selected 12, representing 9 ions or atoms, in order to analyse line
  intensities, shifts and widths in polar coronal holes as well as in the
  normal quiet Sun. We find that coronal lines show a distinct blueshift
  in coronal holes relative to the quiet Sun at equal heliospheric
  angle, while there is no evidence for such a shift for lines formed at
  temperatures below 10^5 K. The widths of lines formed at temperatures
  above 3 - 10^4 K are slightly increased inside the coronal hole,
  but unaffected for lower temperatures. Intensity measurements clearly
  show the center-to-limb variation, as well as an intensity diminution
  inside the coronal hole for lines formed above approximately 10^5 K.

Title: Outflow Velocities at the Base of a Polar Coronal Hole During
    the 1998 Total Eclipse
Authors: Patsourakos, S.; Vial, J. -C.; Gabryl, J. -R.; Koutchmy,
   S.; Schühle, U.
Bibcode: 1999SSRv...87..291P
Altcode:
  Polar coronal holes represent the most convincing site from which the
  high-speed solar wind originates. Here we report high-accuracy Doppler
  shifts measured in the O VI (1037.6 Å) line obtained by SUMER on SOHO
  inside an interplume region within the south polar coronal hole. We
  infer limits on the outflow velocity and draw hints about the flow
  geometry.

Title: Signatures of Coronal Hole Spectra Between 660 Å and 1460
    Å Measured with SUMER on SOHO
Authors: Schühle, U.; Curdt, W.; Wilhelm, K.; Solanki, S. K.;
   Stucki, K.
Bibcode: 1999SSRv...87..299S
Altcode:
  Spectra of the northern polar coronal hole measured with the SUMER
  spectrometer on SOHO on 25 October 1996 are analyzed. We present spectra
  taken at locations on the solar disk where part of the spectrometer
  slit intersects a polar coronal hole region and an area of brighter
  emission from outside of the coronal hole area. By comparing the line
  intensities between the parts of the spectrum taken inside the "dark"
  area of the coronal holes and the brighter regions, we work out the
  signatures of the specific coronal hole in the chromosphere, transition
  region and lower corona. We find that emissions of neutral atom lines,
  of which there are many in the spectrum of SUMER, show no difference
  between the coronal hole and the bright boundary areas, whereas all
  ionized species show strong intensity enhancements, including the
  continuum emissions of carbon and hydrogen. These enhancements are
  larger than in normal quiet Sun areas.

Title: Solar irradiances of UV and EUV lines during the minimum of
    the sunspot activity in 1996
Authors: Wilhelm, K.; Lemaire, P.; Dammasch, I. E.; Hollandt, J.;
   Schühle, U.; Curdt, W.; Kucera, T.; Hassler, D. M.; Huber, M. C. E.
Bibcode: 1999AdSpR..24..229W
Altcode:
  Full Sun observations in UV and EUV emission lines were performed
  by SUMER (Solar Ultraviolet Measurements of Emitted Radiation) on
  SOHO (Solar and Heliospheric Observatory) in 1996. The radiometric
  preflight calibration of SUMER is traceable to a primary radiometric
  source standard - the electron storage ring BESSY. Based on this
  calibration and on its inflight refinements, the irradiance values at
  SOHO have been obtained for the lines He i (λ584.33), O v (λ629.74),
  Ne viii (λ770.41), S v (λ786.47), O iv (λ787.72), S vi (λλ933.39,
  944.52), H i Ly ɛ (λ937.80), C iii (λ977.04), N v (λ1238.81),
  Si i (λ1256.52), and C iv (λ1548.20), and the continuum near 1549
  Å. In this contribution, we compare our measurements with other recent
  irradiance determinations and discuss, in particular, the observations
  in the C iv line.

Title: The Electron Pressure in the Solar Lower Transition Region
    Determined from O V and Si III Density-sensitive Line Ratios
Authors: Doschek, G. A.; Feldman, U.; Laming, J. M.; Warren, H. P.;
   Schüle, U.; Wilhelm, K.
Bibcode: 1998ApJ...507..991D
Altcode:
  We determine the electron density at the temperatures of formation
  of O<SUP>+4</SUP> and Si<SUP>+2</SUP> ions, which are about 2.5 ×
  10<SUP>5</SUP> and 3.2 × 10<SUP>4</SUP> K in ionization equilibrium,
  respectively. These temperatures occur in the lower transition
  region of the Sun's atmosphere and allow a test of the often invoked
  assumption of constant pressure in quiet-Sun models. The O<SUP>+4</SUP>
  density is determined from a density-sensitive spectroscopic O V
  line ratio involving 2s2p<SUP>3</SUP>P-2p<SUP>2</SUP><SUP>3</SUP>P
  transitions that fall near 760 Å. The Si<SUP>+2</SUP> density is
  determined from a density-sensitive Si III line ratio within the
  3s3p<SUP>3</SUP>P-3p<SUP>2</SUP><SUP>3</SUP>P multiplet near 1300
  Å. There are few available line ratio techniques for determining
  the density and hence electron pressure in the quiet-Sun and coronal
  hole transition regions using lines emitted by the same ion, and
  determining these quantities is the principal motivation for this
  work. The spectra used in our analysis were obtained from the Solar
  Ultraviolet Measurements of Emitted Radiation (SUMER) experiment on the
  Solar and Heliospheric Observatory (SOHO). We determine the electron
  density and pressure in typical quiet-Sun/coronal hole regions, and
  densities in active region brightenings and in an explosive event. Our
  O V and Si III results indicate that constant pressure is valid or
  nearly valid in quiet-Sun lower transition regions, although there
  are complications arising from the weakness of a key Si III line in
  the quiet-Sun disk spectra. We also discuss our results in light of
  other density measurements and theories regarding the structure and
  heating of the transition region.

Title: Coronal Composition above the Solar Equator and the North Pole
    as Determined from Spectra Acquired by the SUMER Instrument on SOHO
Authors: Feldman, U.; Schühle, U.; Widing, K. G.; Laming, J. M.
Bibcode: 1998ApJ...505..999F
Altcode:
  Using spectra obtained by the SUMER instrument on the Solar and
  Heliospheric Observatory (SOHO) we have determined the composition of
  the bulk of the coronal plasma in the vicinity of the solar surface
  over a polar coronal hole and an equatorial region. Our measurements
  show that although low first ionization potential (FIP) elements are
  enriched by about a factor of 4 in the corona above the quiet equatorial
  region, little or no enrichment exists above the north polar coronal
  hole. These observations are in good agreement with the Ulysses in
  situ observations in both fast speed and slow speed winds.

Title: SUMER Measurements of Nonthermal Motions: Constraints on
    Coronal Heating Mechanisms
Authors: Chae, Jongchul; Schühle, Udo; Lemaire, Philippe
Bibcode: 1998ApJ...505..957C
Altcode:
  We have determined nonthermal velocities in the quiet Sun at
  temperatures between 10<SUP>4</SUP> K and 2 × 10<SUP>6</SUP> K by
  measuring the widths of a number of EUV and far-ultraviolet (FUV)
  lines taken with SUMER on board the SOHO spacecraft. The broadenings
  owing to the SUMER instrument and the finite opacity in each line
  have been carefully examined. The nonthermal velocity at temperatures
  below 2 × 10<SUP>4</SUP> K is smaller than 10 km s<SUP>-1</SUP>. The
  velocity increases with temperature, reaches a peak value of 30
  km s<SUP>-1</SUP> around 3 × 10<SUP>5</SUP> K, and then decreases
  with the temperature. The coronal nonthermal velocity is about 20 km
  s<SUP>-1</SUP>. There exists a strong correlation between intensity
  and nonthermal velocity at temperatures 2 × 10<SUP>4</SUP>-1 ×
  10<SUP>5</SUP> K. The correlation at higher temperatures weakens as
  temperature increases. Furthermore, there is a spatial correlation
  between the nonthermal velocities inferred from a set of any two lines
  with temperatures below 2 × 10<SUP>5</SUP> K. Neither significant
  center-to-limb variation nor meaningful dependence on the integration
  time was found from the measured nonthermal velocities. We have
  discovered the existence of high-velocity components in the observed
  S VI λ933.4 line profiles. The average nonthermal velocity and
  intensity fraction of this S VI line high-velocity component are found
  to be 55 km s<SUP>-1</SUP> and 0.25, respectively. <P />Observational
  characteristics of nonthermal motions carry some problems that should be
  solved when interpreting observed nonthermal motions in terms of either
  unresolved loop flows or Alfvén waves. The isotropic and very small
  scale nature of the observed nonthermal motions appears to be suited to
  the MHD turbulence interpretation of nonthermal motions. The turbulent
  heating rates inferred from the measured nonthermal motions can account
  for the radiative loss throughout the transition region and corona if
  the nonthermal motions are truly turbulent motions whose mechanical
  energy is injected at a scale of 1000 km (Kolmogorov-type turbulence)
  or 15 km (Kraichnan-type turbulence). The existence of high-velocity
  components at temperatures 6 × 10<SUP>4</SUP>-2 × 10<SUP>5</SUP>
  K appears as observational evidence supporting nanoflare heating at
  these temperatures.

Title: Chromospheric Upflow Events Associated with Transition Region
    Explosive Events
Authors: Chae, Jongchul; Wang, Haimin; Lee, Chik-Yin; Goode, Philip
   R.; Schühle, Udo
Bibcode: 1998ApJ...504L.123C
Altcode:
  Transition region explosive events are considered to be a manifestation
  of small-scale magnetic reconnection ubiquitously occurring--even in
  the quiet Sun. In this paper, we report a close association between
  transition region explosive events and chromospheric upflow events seen
  in Hα. From a comparison of the Big Bear Solar Observatory (BBSO)
  Hα spectrograph data and the Solar and Heliospheric Observatory
  (SOHO) / Solar Ultraviolet Measurements of Emitted Radiation (SUMER)
  data, we found a succession of chromospheric upflow events at sites
  where repeated explosive events occurred. Individual chromospheric
  events appear as compact dark features that are best visible in
  Hα-0.5 Å and that have a size of 2"-3" and a lifetime of 1-2
  minutes. They are characterized by an upward motion of 15-30 km
  s<SUP>-1</SUP>, a temperature of 10<SUP>4</SUP> K, a mass density
  of 1×10<SUP>-13</SUP> g, and a nonthermal velocity less than 10
  km s<SUP>-1</SUP>. Unlike spicules, which display descending motion
  following their ascending phase, these upflow events are not followed
  by noticeable redshifts. ``Hα jets'' at -1.0 Å studied by Wang et
  al. appear to be a special case of this kind of chromospheric upflow
  event. The physical characteristics of chromospheric upflow events and
  their close association with transition region explosive events suggest
  that chromospheric upflow events may be the manifestation of cool plasma
  material flowing into magnetically diffusive regions, while explosive
  events represent hot plasma material flowing out of the same regions.

Title: The Si/Ne Abundance Ratio in Polar Coronal Hole and Quiet-Sun
    Coronal Regions
Authors: Doschek, G. A.; Laming, J. M.; Feldman, U.; Wilhelm, K.;
   Lemaire, P.; Schühle, U.; Hassler, D. M.
Bibcode: 1998ApJ...504..573D
Altcode:
  Using spectra obtained from the Solar Ultraviolet Measurements
  of Emitted Radiation (SUMER) spectrometer flown on the Solar and
  Heliospheric Observatory (SOHO) spacecraft, we determine the Si/Ne
  abundance ratio in diffuse, interplume polar coronal hole regions,
  as well as the ratio relative to quiet-Sun coronal regions. Ne has
  the second highest first ionization potential (FIP) of solar abundant
  elements, and Si is a low-FIP element. Thus the Si/Ne ratio is a
  sensitive indicator of abundance variations due to the FIP effect. We
  develop new spectroscopic diagnostics for the determination of the
  Si/Ne abundance ratio. Assuming ionization equilibrium, we find that
  the Si/Ne abundance ratio in interplume polar coronal hole regions is
  about a factor of 2 greater than the photospheric value and is close
  to or the same as in coronal quiet-Sun regions. This result pertains
  to the electron temperature range 5-8 × 10<SUP>5</SUP> K. However,
  the combined atomic physics, instrumental, and statistical uncertainty
  in this result is about a factor of 2, and therefore this observed
  enhancement is consistent with no enhancement in the polar hole
  abundances. Nevertheless, our results follow the same trend, i.e., a
  greater than photospheric abundance ratio of low-FIP elements in the
  corona relative to high-FIP elements, as found from other abundance
  measurements in the corona that involve different atomic physics and
  different instruments. Therefore we feel that our results reflect
  an actual abundance enhancement, despite being within an uncertainty
  level bar that encompasses photospheric abundances. We also examine
  the Ne/Mg abundance ratio over a 24.5 hr observation and find no
  significant abundance variations. (Mg is a low-FIP element.) Thus,
  no large transient abundance variations appear to occur on timescales
  shorter than about a day, although this result is based on only
  one observation. From lines of Mg VII, Mg VIII, Mg IX, and Mg X we
  find that the electron temperature along the line of sight increases
  with height above the limb over the polar coronal holes, as has been
  previously reported. We determine the emission measure distribution as
  a function of height from Mg VII, Mg VIII, and Mg X lines. We determine
  average temperatures along the line of sight over the polar holes from
  Ne VIII/Ne VII, Mg VIII/Mg VII, and Si VIII/Si VII line ratios. We also
  discuss the temperature properties of the coronal hole and quiet-Sun
  regions using forbidden lines of Fe X and Fe XI. We comment on the
  possibility that ionization equilibrium is not valid in polar coronal
  hole regions, a possible scenario in light of recent observations that
  show outflows in coronal holes beginning at about the temperature of
  formation of Ne VIII.

Title: High-Temperature Lines in SUMER Spectra Recorded Above a
    Bright Solar Active Region
Authors: Feldman, U.; Curdt, W.; Doschek, G. A.; Schühle, U.; Wilhelm,
   K.; Lemaire, P.
Bibcode: 1998ApJ...503..467F
Altcode:
  We identify spectral lines emitted by solar abundant elements due
  primarily to transitions within the 2s<SUP>2</SUP>2p<SUP>k</SUP> and
  3s<SUP>2</SUP>3p<SUP>k</SUP> (where k = 1, 5) ground configurations
  of ions that are formed in ionization equilibrium between 2 ×
  10<SUP>6</SUP> and 8 × 10<SUP>6</SUP> K. The transitions were
  identified in spectra of a bright active region recorded 1997
  September 6, by the Solar Ultraviolet Measurements of Emitted Radiation
  Spectrometer (SUMER) flown on the Solar and Heliospheric Observatory
  (SOHO). Some of these lines provide useful plasma diagnostic tools
  for measuring the physical conditions in the solar corona.

Title: Evidence in Support of the ``Nanoflare'' Picture of Coronal
    Heating from SUMER Data
Authors: Judge, P. G.; Hansteen, V.; Wikstøl, Ø.; Wilhelm, K.;
   Schühle, U.; Moran, T.
Bibcode: 1998ApJ...502..981J
Altcode:
  We study high signal-to-noise profiles of O IV emission lines obtained
  using the SUMER instrument on SOHO. Data for the quiet Sun obtained
  close to the disk center and at the solar limb were acquired. After
  careful data processing in which disk data were analyzed differentially
  against limb data, we find a systematic correlation between a
  density-sensitive emission-line ratio and Doppler shift across the
  same emission-line profiles. While unidentified blended lines cannot be
  completely discounted, the data suggest that the effects of such blends
  are small. Based on theoretical results in an earlier paper, we argue
  that if wave motions are responsible for the observed behavior, then
  the data reveal evidence for compressive waves propagating downward
  from the corona to the chromosphere. This analysis naturally lends
  support to the dominance of the ``nanoflare'' mechanism for coronal
  heating over other theories that invoke upward wave propagation,
  but other mechanisms capable of generating downward-propagating waves
  cannot be discounted. If, instead, steady flows are the cause of the
  observed behavior, such as return flows from spicules, then they must
  be such that the density is higher in the downflowing plasma. While
  these particular data do not allow us to discriminate between waves
  or steady flows, additional data from SOHO should be able to address
  this problem. This work required and achieved very accurate wavelength
  calibrations (better than 1/5 of a pixel on the detectors), taking
  SUMER close to its observational capabilities. We therefore present
  the elements of the analysis and calibration of SUMER data that may
  be of interest to other users.

Title: Solar irradiances and radiances of UV and EUV lines during
    the minimum of sunspot activity in 1996
Authors: Wilhelm, K.; Lemaire, P.; Dammasch, I. E.; Hollandt, J.;
   Schuehle, U.; Curdt, W.; Kucera, T.; Hassler, D. M.; Huber, M. C. E.
Bibcode: 1998A&A...334..685W
Altcode:
  Full Sun observations in UV and EUV emission lines were performed
  by SUMER (Solar Ultraviolet Measurements of Emitted Radiation) on
  SOHO (Solar and Heliospheric Observatory) in 1996. The radiometric
  pre-flight calibration of SUMER is traceable to a primary radiometric
  source standard - the electron storage ring BESSY. Based on this
  calibration, the irradiance values at SOHO and at 1 AU have been
  obtained for the lines He i (lambda 584.33 { Angstroms}), O v (lambda
  629.74 { Angstroms}), Ne viii (lambda 770.41 { Angstroms}), S v (lambda
  786.47 { Angstroms}), O iv (lambda 787.72 { Angstroms}), S vi (lambda
  lambda 933.39, 944.52 { Angstroms}), H i Ly epsilon (lambda 937.80 {
  Angstroms}), C iii (lambda 977.04 { Angstroms}), N v (lambda 1238.81
  { Angstroms}), Si i (lambda 1256.52 { Angstroms}), and C iv (lambda
  1548.20 { Angstroms}). The spatially resolved measurements allowed
  good estimates to be made of the active region contributions to the
  irradiance of the quiet Sun. The centre-to-limb radiance variations of
  these lines have also been obtained from these measurements. For quiet
  solar conditions, a radiance spectrum was determined for wavelengths
  from 800 { Angstroms} to 1500 { Angstroms} near the centre of the
  solar disk.

Title: Solar H i Lyman alpha full disk profile obtained with the
    SUMER/SOHO spectrometer
Authors: Lemaire, P.; Emerich, C.; Curdt, W.; Schuehle, U.; Wilhelm, K.
Bibcode: 1998A&A...334.1095L
Altcode:
  An uncalibrated solar hydrogen Lyman alpha profile was obtained with
  the use of the spectrometer on SOHO. The collection of the light
  scattered by the telescope permitted to average the profile over
  the full solar disk. The profile taken at the L<SUB>1</SUB> Sun-Earth
  Lagrangian position is free of the central geocoronal absorption. Then,
  taking advantage of the absolute flux measured by the SOLSTICE/UARS
  spectrometer, an absolute line profile intensity is derived, and is
  compared with previous observations at minimum solar activity.

Title: Photospheric Magnetic Field Changes Associated with Transition
    Region Explosive Events
Authors: Chae, Jongchul; Wang, Haimin; Lee, Chik-Yin; Goode, Philip
   R.; Schühle, Udo
Bibcode: 1998ApJ...497L.109C
Altcode:
  From a comparison of the Solar and Heliospheric Observatory SUMER
  spectral data and a time series of Big Bear Solar Observatory
  magnetograms, we present observational clues to the physical origin of
  transition region explosive events. First, explosive events rarely occur
  in the interior of strong magnetic flux concentrations but rather are
  preferentially found in regions with weak and mixed polarity fluxes that
  display magnetic neutral lines. Second, the majority of explosive events
  happen during the ``cancellation'' of photospheric magnetic flux. Third,
  there is a strong tendency for explosive events to occur repeatedly, as
  bursts, while local photospheric magnetic flux continuously decreases
  because of cancellation. These results strongly support the idea that
  transition region explosive events are a manifestation of magnetic
  reconnection occurring in the quiet Sun. Furthermore, one may infer from
  the third result that the explosive events represent repetitive fast
  magnetic reconnections in the transition region, which are initiated
  by slow magnetic reconnections occurring beneath.

Title: The Magnetic Reconnection Explorer (MAGREX)
Authors: Schühle, U.; Antionchos, S. K.; Barbee, T. W., Jr.; Bixler,
   J. V.; Brown, C. M.; Carter, P. H., II; Curdt, W.; Davila, J. M.;
   Doschek, G.; Feldman, U.; Goldstein, W. H.; Kordas, J.; Lemaire, P.;
   Mariska, J. T.; Marsch, E.; Moses, J. D.; Seely, J. F.; Wilhelm, K.;
   Woods, T. N.
Bibcode: 1998ESASP.417..289S
Altcode: 1998cesh.conf..289S
  No abstract at ADS

Title: Oscillations in Chromosphere and Transition Region Based on
    SUMER Measurements
Authors: Kucera, A.; Curdt, W.; Rybák, J.; Schühle, U.; Wöhl, H.
Bibcode: 1998ASPC..155..351K
Altcode: 1998sasp.conf..351K
  No abstract at ADS

Title: Solar Radiometry with the Telescope and Vaccum-Ultraviolet
    Spectrometer Sumer on the Solar and Heliospheric Observatory (SOHO)
Authors: Hollandt, J.; Schuhle, U.; Curdt, W.; Dammasch, I. E.;
   Lamaire, P.; Wihelm, K.
Bibcode: 1998Metro..35..671H
Altcode:
  No abstract at ADS

Title: VLA-SOHO Observations of Evolving Coronal Structures on the Sun
Authors: Willson, R. F.; Lang, K. R.; Thompson, B.; Schuehle, U.;
   Zarro, D. M.
Bibcode: 1998ASPC..154..727W
Altcode: 1998csss...10..727W
  Very Large Array (VLA) observations at 3.5, 6.2, and 91.6 cm wavelength
  have been combined with EUV spectroheliograms from the Solar and
  Heliospheric Observatory (SOHO) Coronal Diagnostic Spectrometer (CDS)
  and Extreme Ultraviolet Telescope (EIT) to study evolving sources in the
  transition region and corona above a solar active region. In some cases,
  transient events, lasting minutes to tens of minutes, were observed
  at both radio and EUV wavelengths, while other events were detected
  in only one spectral domain. The combined data sets suggest that the
  EUV-associated microwave sources are produced by thermal gyroresonance
  or nonthermal gyrosynchrotron radiation, primarily in regions of high
  magnetic field strength near sunspots. Observations at 91.6 cm also
  show the sudden appearance of a low-lying, nonthermal source in the
  low corona around the time that cool, outwardly-propagating plasma
  was detected by the SOHO/EIT.

Title: Observations of the solar atmosphere from the Solar and
    Heliospheric Observatory (SOHO).
Authors: Schühle, U.
Bibcode: 1997JXST....7..249S
Altcode:
  The Solar and Heliospheric Observatory (SOHO) spacecraft was launched
  on December 2, 1995, into a halo orbit around the first Lagrangian
  Point L1 between Sun and Earth, carrying into space a payload of twelve
  Sun observing instruments. Among them is a set of four complementary
  telescope/spectrometers to study phenomena and dynamics of the Sun's
  atmosphere in the far or extreme ultraviolet: The Extreme-Ultraviolet
  Imaging Telescope (EIT), the Coronal Diagnostic Spectrometer (CDS),
  the Solar Ultraviolet Measurements of Emitted Radiation (SUMER), and
  the Ultraviolet Coronagraph Spectrometer (UVCS). The spectral coverage
  of these instruments, which extents from 151 to 1610 Å, allows remote
  sensing investigations of the solar atmosphere by means of spectroscopic
  and imaging techniques with a spatial resolution down to 1 arcsec. Each
  one of these instruments by itself is a technological achievement
  making use of normal incidence, grazing incidence, or multilayer optical
  techniques to cover the appropriate spectral ranges for each scientific
  objective. Many of the plasma diagnostic studies have been carried
  out during the first months of the mission, and this contribution will
  give an overview of the capabilities of each instrument and the types
  of observations being made by individual and joint operations.

Title: The solar disk spectrum between 660 and 1175 Anstroms (first
    order) obtained by SUMER on SOHO
Authors: Curdt, W.; Feldman, U.; Laming, J. M.; Wilhelm, K.; Schuehle,
   U.; Lemaire, P.
Bibcode: 1997A&AS..126..281C
Altcode:
  SUMER -- Solar Ultraviolet Measurements of Emitted Radiation -- onboard
  of SOHO -- Solar and Heliospheric Observatory -- obtained its first
  spectrum on January 25, 1996 near the north polar limb. The range
  from 660 Angstroms to 1175 Angstroms which has never before been
  observed with such a good spectral resolution contains a wealth of
  spectroscopic details. Identification of about 400 lines in this
  spectral range is given. We list the wavelengths of identified
  transitions and provide their absolute peak intensities. General
  spectral features of the most abundant elements H, He, C, N, O,
  Ne, Mg, Si, S, Ar, and Fe are described. In this spectral range
  many density- and temperature-sensitive line pairs are found. It is
  shown in examples how they can be used as diagnostic tools. Table
  1 and Fig.nearlimb are also available in digital form at the CDS
  via anonymous ftp to cdsarc.u-strasbg. fr (130.79.128.5) or via
  http://cdsweb.u-strasbg.fr/Abstract.html

Title: The Off-Limb Behaviour of the Solar Transition Region FIP
    Effect
Authors: Laming, J. M.; Feldman, U.; Drake, J. J.; Schuhle, U.; Curdt,
   W.; Wilhelm, K.; Lemaire, P.
Bibcode: 1997AAS...191.7301L
Altcode: 1997BAAS...29.1320L
  We investigate the behaviour of the solar FIP effect (the abundance
  enhancement of elements with first ionization potential &lt; 10 eV by
  factor of 3-4 in the corona with respect to photospheric values) with
  height above the limb in a region of diffuse quiet corona observed
  by the SUMER instrument on SOHO. Line ratios formed at log T &gt;
  5.8 show coronal abundances for all heights. Line ratios formed at
  lower temperatures are consistent with coronal abundances well off the
  limb, with the apparent magnitude of the FIP enhancement decreasing
  by a factor of 1.5 - 2 as one approaches the solar limb. Thus our
  observations support a spatial variation in the quiet sun transition
  region FIP effect inferred previously from studies of the full disk
  solar spectrum (Laming, Drake, &amp; Widing 1995, ApJ, 443, 416
  and references therein). This result adds to the probability that
  emission from the solar disk transition region and corona originates
  from qualitatively different structures for values of log T {&lt;atop
  &gt;} 5.8, having different FIP effects.

Title: Sonnenradiometrie mit SUMER auf SOHO.
Authors: Hollandt, J.; Curdt, W.; Schühle, U.; Wilhelm, K.
Bibcode: 1997PhyBl..53.1101H
Altcode: 1997PhB....53.1101H
  No abstract at ADS

Title: A Coronal Spectrum in the 500--1610 Angstrom Wavelength Range
    Recorded at a Height of 21,000 Kilometers above the West Solar Limb
    by the SUMER Instrument on Solar and Heliospheric Observatory
Authors: Feldman, U.; Behring, W. E.; Curdt, W.; Schühle, U.; Wilhelm,
   K.; Lemaire, P.; Moran, T. M.
Bibcode: 1997ApJS..113..195F
Altcode:
  We present a solar coronal spectrum recorded by the extreme UV
  spectrometer SUMER on the Solar and Heliospheric Observatory. The
  spectrum was taken between 21:28 UT on 1996 June 25 and 02:47 UT on
  1996 June 26, at a height of 21,000 km above the west equatorial limb
  with the slit oriented in the north-south direction. At the time of
  the observations the Sun was rather quiet, and the west limb appeared
  ``devoid of any activity.'' The spectrum, which covers the 500-1610
  Å wavelength range, originates from plasmas with temperatures
  ranging between 1.5 × 10<SUP>4</SUP> and 1.5 × 10<SUP>6</SUP>
  K. Identification of lines originating from different temperature
  regimes is facilitated by the appearance of their intensity along the
  300" long slit. <P />Well over 800 lines have been found, many of which
  were not previously observed. We present the entire spectrum and discuss
  line identifications. A table of the wavelengths of lines observed,
  with their identifications and peak intensities, is provided. Although
  we have identified lines previously detected in laboratory plasmas and
  a number of new lines not previously observed, over 40% of the SUMER
  lines remain unidentified. Among the newly detected lines, some have
  a potential as plasma density diagnostics.

Title: Observations of Polar Plumes with the SUMER Instrument on SOHO
Authors: Hassler, D. M.; Wilhelm, K.; Lemaire, P.; Schühle, U.
Bibcode: 1997SoPh..175..375H
Altcode:
  We present new observations of O vi 1032 Å line profiles in polar
  plumes, and inter-plume regions, on the disk and above the limb in
  the north coronal hole obtained with the SUMER (Solar Ultraviolet
  Measurements of Emitted Radiation) instrument on the SOHO (Solar and
  Heliospheric Observatory) spacecraft. On 22 May 1996, a 5 x 5 arc min
  spectroheliogram was scanned above the north polar coronal hole with
  the entrance slit extending from 1.03 to 1.33 solar radii with 1.5 arc
  sec spatial resolution and ≈ 0.044 Å per pixel spectral resolution
  in the wavelength range 1020-1040 Å. Detailed plume structure in
  O vi 1032 Å can be seen extending beyond 1.3 solar radii, with
  intensities in the plume regions 10-50% brighter, but line widths
  10-15% narrower, than the inter-plume regions. Possible explanations
  for this observed anti-correlation between line width and intensity
  in the plume and inter-plume regions are discussed. We conclude that
  the source of the high-speed solar wind may not be polar plumes, but
  the inter-plume lanes associated with open magnetic field regions of
  the chromospheric network.

Title: Laboratory Identification of Temperature Diagnostic Si VII and
    S IX Lines Present in the Solar Coronal Spectra Measured by SUMER/SOHO
Authors: Kink, I.; Jupén, C.; Engström, L.; Feldman, U.; Laming,
   J. M.; Schühle, U.
Bibcode: 1997ApJ...487..956K
Altcode:
  The solar coronal spectrum between 500 and 1610 Å and at a
  height of 21,000 km above the west equatorial limb has recently
  been recorded by the SUMER instrument on SOHO. Using laboratory
  spectra obtained with the beam-foil technique, we report
  the identification of 32 lines observed in this spectrum as
  2s<SUP>2</SUP>2p<SUP>3</SUP>3s-2s<SUP>2</SUP>2p<SUP>3</SUP>3p and
  2s<SUP>2</SUP>2p<SUP>3</SUP>3p-2s<SUP>2</SUP>2p<SUP>3</SUP>3d
  transitions in Si VII and S IX. Theoretical gA-values
  and branching ratios for the observed lines, obtained from
  semiempirical configuration interaction calculations, are also
  presented. Intensity ratios between the 2s<SUP>2</SUP>2p<SUP>4</SUP>
  <SUP>3</SUP>P<SUB>1</SUB>-2s<SUP>2</SUP>2p<SUP>4</SUP>
  <SUP>1</SUP>S<SUB>0</SUB> forbidden transition and transition from
  the newly identified high-excitation lines that appear in the same
  wavelength range are temperature sensitive. Calculations of the
  intensity ratios between the forbidden line and the high-excitation
  lines for three temperatures are presented. A comparison between the
  calculations and some of the SUMER observations is provided.

Title: Radiometric calibration of SUMER: refinement of the laboratory
    results under operational conditions on SOHO
Authors: Wilhelm, Klaus; Lemaire, Philippe; Feldman, Uri; Hollandt,
   Jörg; Schühle, Udo; Curdt, Werner
Bibcode: 1997ApOpt..36.6416W
Altcode:
  No abstract at ADS

Title: Electron Density Diagnostics for the Solar Upper Atmosphere
    from Spectra Obtained by SUMER/SOHO
Authors: Laming, J. M.; Feldman, U.; Schühle, U.; Lemaire, P.; Curdt,
   W.; Wilhelm, K.
Bibcode: 1997ApJ...485..911L
Altcode:
  We evaluate the electron density in various solar regions above the
  limb observed by the Solar Ultraviolet Measurement of Emitted Radiation
  (SUMER) instrument on SOHO. We find in general good agreement among
  line ratios from Be-, B-, N-, and Mg-like ions, giving densities of
  order 10<SUP>8</SUP> cm<SUP>-3</SUP>.

Title: Turbulent Velocities and Ion Temperatures in the Solar Corona
    Obtained from SUMER Line Widths
Authors: Seely, J. F.; Feldman, U.; Schühle, U.; Wilhelm, K.; Curdt,
   W.; Lemaire, P.
Bibcode: 1997ApJ...484L..87S
Altcode:
  Turbulent plasma velocities and ion temperatures were determined from
  the line widths recorded by the Solar Ultraviolet Measurements of
  Emitted Radiation instrument on the Solar and Heliospheric Observatory
  spacecraft. From the widths of the lines of five light elements
  (Ne, Na, Mg, Si, and S) and a heavy element (Fe), it was possible
  to determine the contributions of turbulent plasma motion and ion
  thermal motion to the line widths. The results indicated that the
  turbulent velocity was approximately 22 km s<SUP>-1</SUP> at 30"
  above the limb and decreased to less than 10 km s<SUP>-1</SUP> at 109"
  and 209" above the limb. At 30" above the limb, the ion temperatures
  of the hotter lines were comparable to the electron temperatures for
  ionization equilibrium. The ion temperatures of the cooler lines were
  higher than the ionization equilibrium temperatures; at 109" and 209"
  above the limb, the ion temperatures were at least a factor of 2.5
  higher than the ionization equilibrium temperatures.

Title: Electron Densities in the Solar Polar Coronal Holes from
    Density-Sensitive Line Ratios of Si VIII and S X
Authors: Doschek, G. A.; Warren, H. P.; Laming, J. M.; Mariska, J. T.;
   Wilhelm, K.; Lemaire, P.; Schühle, U.; Moran, T. G.
Bibcode: 1997ApJ...482L.109D
Altcode:
  We derive electron densities as a function of height in the north and
  south polar coronal holes from a forbidden spectral line ratio of Si
  VIII. Si VIII is produced at about 8 × 10<SUP>5</SUP> K in ionization
  equilibrium. We also derive densities from a similar line ratio of S X
  (1.3 × 10<SUP>6</SUP> K). The spectra were obtained with the Solar
  Ultraviolet Measurements of Emitted Radiation spectrometer flown on
  the Solar and Heliospheric Observatory spacecraft. In addition to the
  primary mechanism of electron impact excitation, the derivation of
  theoretical level populations for Si VIII and S X includes both proton
  and resonance capture excitation. We compare the coronal hole results
  to quiet-Sun coronal measurements obtained outside the east and west
  limbs. We find for distances of a few arcseconds outside the solar
  limb that the average line-of-sight electron densities in the coronal
  holes are about a factor of 2 lower than in quiet-Sun regions. The
  decrease of density with height is exponential in the polar holes. We
  also confirm the result known from a variety of earlier observations
  that the temperature of most of the plasma in coronal holes does not
  exceed about 10<SUP>6</SUP> K.

Title: Translimb Spectroscopy with SOHO/SUMER
Authors: Ayres, T. R.; Lemaire, P.; Schuhle, U.; Wilhelm, K.; Ruedi,
   I.; Solanki, S.
Bibcode: 1997SPD....28.0104A
Altcode: 1997BAAS...29..879A
  We have used SUMER to obtain deep exposures of the 1300--1400 Angstroms
  spectrum, at the extreme limb and off-limb. Previous ``translimb''
  studies in the thermal infrared had revealed remarkable extensions
  of cold material (T ~ 3000 K)---traced by carbon monoxide emission
  lines---into the heart of the hot chromosphere. A main objective of
  our program was to search for corresponding far-UV signatures of the
  ``thermally-bifurcated'' low chromosphere; for example, radiatively
  fluoresced emissions of the CO A--X 4th-positive system (collisional
  excitation would be negligible in cold gas). We conducted two separate
  observing programs with SUMER. Both made use of the 1('') -diameter
  circular aperture, translated across the limb in the minimum motor
  step increments of 0.('') 375, along the central meridian in the
  Northern polar coronal hole. The first program executed for nine hours
  beginning 19UT 25 Oct 1996. The full wavelength range was 1340--1400
  Angstroms. It was recorded in two overlapping segments, placing key
  regions of the spectrum alternately on the KBr and bare parts of
  the detector, to help isolate 2nd-order features. Each segment was
  integrated for 500 s, and 32 pairs were obtained to span a 12('')
  swath centered on the optical limb. The second program was conducted
  00--09UT 01 Dec 1996. It consisted of a single wavelength setting
  (1300--1340 Angstroms) with exposure time 500 s, but twice the spatial
  coverage of the earlier series: 64 steps, for a total displacement
  of 24('') . The strong chromospheric resonance lines of atomic oxygen
  (1302--1305 Angstroms) and ionized carbon (1334--1335 Angstroms) were
  observed on the bare part of the MCP camera. We report our progress
  in cataloging the rich, diverse translimb emission spectrum; and our
  efforts to deduce fundamental properties of the thermally heterogeneous
  chromosphere. [-3mm] SOHO is a project of international cooperation;
  the participation of TRA was supported by NASA grant NAG5-3226.

Title: New Insights into the Physical Mechanisms of Polar Plumes
    with Observations from the SUMER Instrument on SOHO
Authors: Hassler, Donald M.; Wilhelm, Klaus; Lemaire, Philippe;
   Schuehle, Udo
Bibcode: 1997SPD....28.0802H
Altcode: 1997BAAS...29..912H
  SUMER (Solar Ultraviolet Measurements of Emitted Radiation)
  line profiles above the limb in coronal holes are important for
  constraining thermodynamic models governing the outflow of the solar
  wind. Observational constraints in terms of thermal and nonthermal
  velocities, and upper limits on wave velocity amplitudes can be directly
  compared with in-situ observations. We present new observations of
  line profiles in polar plumes, and inter-plume regions, above the
  limb in coronal holes obtained with the SUMER instrument on the SOHO
  spacecraft. Detailed structure can be seen extending beyond 1.5 solar
  radii (out to the edge of the SUMER field-of-view), with intensities in
  the plume regions roughly 10-50% brighter than the inter-plume regions,
  but line widths in the plumes roughly 10% narrower than the inter-plume
  regions. Possible explanations for this observed anti-correlation
  between line width and intensity, and the correspondence with observed
  in-situ solar wind signatures will be discussed.

Title: VizieR Online Data Catalog: Solar disk spectrum (660-1175A)
    (Curdt+ 1997)
Authors: Curdt, W.; Feldman, U.; Laming, J. M.; Wilhelm, K.; Schuehle,
   U.; Lemaire, P.
Bibcode: 1997yCat..41260281C
Altcode:
  The near-limb quiet-Sun spectrum recorded on January 25, 1996
  near the solar North pole is presented in tabular form and in
  graphical form. Table 1 - the line list - lists all lines found
  in the spectrum providing absolute peak intensities, measured and
  literature wavelengths, identification, and classification of the
  transition. Fig. 4 is a display the composite spectrum. The most
  prominent lines are labelled. In this figure intensities are given in
  instrumental units and logarithmic scale. (1 data file).

Title: Determination of the Formation Temperature of Si IV in the
    Solar Transition Region
Authors: Doschek, G. A.; Mariska, J. T.; Warren, H. P.; Wilhelm, K.;
   Lemaire, P.; Kucera, T.; Schühle, U.
Bibcode: 1997ApJ...477L.119D
Altcode:
  Using spectra obtained with the Solar Ultraviolet Measurements
  of Emitted Radiation (SUMER) spectrometer flown on the Solar and
  Heliospheric Observatory spacecraft, we deduce the temperature
  of formation of the Si IV ion in the solar transition region
  from the Si IV ultraviolet spectral line intensity ratio, 3p
  <SUP>2</SUP>P<SUB>3/2</SUB>-3d <SUP>2</SUP>D<SUB>3/2,5/2</SUB>/3s
  <SUP>2</SUP>S<SUB>1/2</SUB>-3p <SUP>2</SUP>P<SUB>1/2</SUB>,
  and compare the result to the temperature predicted under the
  assumption of ionization equilibrium. The wavelengths are as
  follows: <SUP>2</SUP>D<SUB>3/2,5/2</SUB>, 1128.325, 1128.340 Å
  <SUP>2</SUP>P<SUB>1/2</SUB>, 1402.770 Å. Ratios are derived for
  typical features of the quiet Sun, such as cell center and network,
  and are systematically higher than those predicted at the 6.3 ×
  10<SUP>4</SUP> K ionization equilibrium temperature of formation
  of Si IV. For most solar features the ratios imply a temperature
  of formation of about 8.5 × 10<SUP>4</SUP> K. The ratios for the
  faintest features imply a temperature of formation of up to 1.6 ×
  10<SUP>5</SUP> K. It is not clear, however, that all the discrepancies
  between the measured and theoretical ratios are due to a temperature
  effect. Accurate temperature measurements are important since a large
  discrepancy from ionization equilibrium has significant implications
  for the physics of the transition region, such as the possible presence
  of nonthermal electrons.

Title: First Results from SOHO on Waves Near the Solar Transition
    Region
Authors: Steffens, S.; Deubner, F. -L.; Fleck, B.; Wilhelm, K.;
   Schuhle, U.; Curdt, W.; Harrison, R.; Gurman, J.; Thompson, B. J.;
   Brekke, P.; Delaboudiniere, J. -P.; Lemaire, P.; Hessel, B.; Rutten,
   R. J.
Bibcode: 1997ASPC..118..284S
Altcode: 1997fasp.conf..284S
  We present first results from simultaneous observations with the
  CDS, EIT and SUMER instruments {please see Solar Physics 162 (1995)
  for a description of the instruments} onboard SOHO and the VTT at
  Tenerife. Our aim is to study the wave propagation, shock formation,
  and transmission properties of the upper chromosphere and transition
  region. The preliminary results presented here include the variation
  of velocity power spectra with height, difference in power between
  internetwork and network regions, and variations in mean flows displayed
  by different spectral lines.

Title: SUMER Observations Detecting Downward Propagating Waves in
    the Solar Transition Region
Authors: Wiskstøl, Ø.; Judge, P. G.; Hansteen, V.; Wilhelm, K.;
   Schühle, U.; Moran, T.
Bibcode: 1997ESASP.404..731W
Altcode: 1997cswn.conf..731W
  No abstract at ADS

Title: Bright Plumes and Dark Lanes as Observed in MgX 625 Å and
    NV 1239 Å in the Solar Polar Corona
Authors: Marsch, E.; Tu, C. -Y.; Wilhelm, K.; Curdt, W.; Schühle,
   U.; Dammasch, I. E.
Bibcode: 1997ESASP.404..555M
Altcode: 1997cswn.conf..555M
  No abstract at ADS

Title: A New Look at the Quiet Sun Network in the Upper Atmosphere
    During a Minimum of Activity Cycle
Authors: Lemaire, P.; Schuehle, U.; Curdt, W.; Wilhelm, K.; Poland,
   A.; Falciani, R.
Bibcode: 1997ESASP.404..517L
Altcode: 1997cswn.conf..517L
  No abstract at ADS

Title: First Results of the SUMER Telescope and Spectrometer on SOHO -
    I. Spectra and Spectroradiometry
Authors: Wilhelm, K.; Lemaire, P.; Curdt, W.; Schühle, U.; Marsch, E.;
   Poland, A. I.; Jordan, S. D.; Thomas, R. J.; Hassler, D. M.; Huber,
   M. C. E.; Vial, J. -C.; Kühne, M.; Siegmund, O. H. W.; Gabriel, A.;
   Timothy, J. G.; Grewing, M.; Feldman, U.; Hollandt, J.; Brekke, P.
Bibcode: 1997SoPh..170...75W
Altcode:
  SUMER - the Solar Ultraviolet Measurements of the Emitted Radiation
  instrument on the Solar and Heliospheric Observatory (SOHO) - observed
  its first light on January 24, 1996, and subsequently obtained a
  detailed spectrum with detector B in the wavelength range from 660
  to 1490 Å (in first order) inside and above the limb in the north
  polar coronal hole. Using detector A of the instrument, this range
  was later extended to 1610 Å. The second-order spectra of detectors
  A and B cover 330 to 805 Å and are superimposed on the first-order
  spectra. Many more features and areas of the Sun and their spectra
  have been observed since, including coronal holes, polar plumes and
  active regions. The atoms and ions emitting this radiation exist at
  temperatures below 2 × 10<SUP>6</SUP> K and are thus ideally suited
  to investigate the solar transition region where the temperature
  increases from chromospheric to coronal values. SUMER can also be
  operated in a manner such that it makes images or spectroheliograms
  of different sizes in selected spectral lines. A detailed line profile
  with spectral resolution elements between 22 and 45 mÅ is produced for
  each line at each spatial location along the slit. From the line width,
  intensity and wavelength position we are able to deduce temperature,
  density, and velocity of the emitting atoms and ions for each emission
  line and spatial element in the spectroheliogram. Because of the high
  spectral resolution and low noise of SUMER, we have been able to detect
  faint lines not previously observed and, in addition, to determine
  their spectral profiles. SUMER has already recorded over 2000 extreme
  ultraviolet emission lines and many identifications have been made on
  the disk and in the corona.

Title: SOHO observations of the north polar solar wind
Authors: Peres, G.; Ciaravella, A.; Betta, R.; Orlando, S.; Reale,
   F.; Kohl, J.; Noci, G.; Fineschi, S.; Romoli, M.; Brekke, P.; Fludra,
   A.; Gurman, J. B.; Lemaire, P.; Schuhle, U.
Bibcode: 1997ESASP.404..587P
Altcode: 1997cswn.conf..587P
  No abstract at ADS

Title: High resolution solar ultraviolet measurements
Authors: Lemaire, P.; Wilhelm, K.; Schühle, U.; Curdt, W.; Poland,
   A. I.; Jordan, S. D.; Thomas, R. J.; Hassler, D. M.; Vial, J. -C.
Bibcode: 1997AdSpR..20.2249L
Altcode:
  The increase of our understanding of the processes acting in the solar
  corona and maintaining it is strongly dependent on the quality of the
  data that are obtained to check theories. The fine structure of the
  solar atmosphere seen from the photosphere and extending to the hottest
  parts of the corona requires data with high resolution in all parameter
  space (angular, spectral and temporal). To constrain the hypotheses that
  are proposed to describe the solar corona, it is necessary to establish
  an accurate energy budget taking into account the processes which are
  acting from the chromosphere to the corona. Some requirements can be
  established and compared with the data collected so far (or about to
  be collected) with the present SUMER (Solar Utraviolet Measurements
  of Emitted Radiations) instrumentation.

Title: First Results of the SUMER Telescope and Spectrometer on SOHO -
    II. Imagery and Data Management
Authors: Lemaire, P.; Wilhelm, K.; Curdt, W.; SchÜle, U.; Marsch,
   E.; Poland, A. I.; Jordan, S. D.; Thomas, R. J.; Hassler, D. M.; Vial,
   J. C.; KÜhne, M.; Huber, M. C. E.; Siegmund, O. H. W.; Gabriel, A.;
   Timothy, J. G.; Grewing, M.
Bibcode: 1997SoPh..170..105L
Altcode:
  SUMER - Solar Ultraviolet Measurements of Emitted Radiation - is not
  only an extreme ultraviolet (EUV) spectrometer capable of obtaining
  detailed spectra in the range from 500 to 1610 Å, but, using the
  telescope mechanisms, it also provides monochromatic images over
  the full solar disk and beyond, into the corona, with high spatial
  resolution. We report on some aspects of the observation programmes
  that have already led us to a new view of many aspects of the Sun,
  including quiet Sun, chromospheric and transition region network,
  coronal hole, polar plume, prominence and active region studies. After
  an introduction, where we compare the SUMER imaging capabilities to
  previous experiments in our wavelength range, we describe the results
  of tests performed in order to characterize and optimize the telescope
  under operational conditions. We find the spatial resolution to be
  1.2 arc sec across the slit and 2 arc sec (2 detector pixels) along
  the slit. Resolution and sensitivity are adequate to provide details
  on the structure, physical properties, and evolution of several solar
  features which we then present. Finally some information is given on
  the data availability and the data management system.

Title: Building the Spectrum of a G2V Star During a Minimum of
    Activity Cycle
Authors: Lemaire, P.; Schuehle, U.; Curdt, W.; Wilhelm, K.; Hassler, D.
Bibcode: 1997ESASP.404..513L
Altcode: 1997cswn.conf..513L
  No abstract at ADS

Title: Investigation of the Dynamics of Chromosphere and Photosphere
    from Spectra Obtained by Parallel Observations using SUMER on SOHO
    and the VTT on Tenerife
Authors: Curdt, W.; Kucera, A.; Rybak, J.; Schuhle, U.; Wohl, H.
Bibcode: 1997ASPC..118..322C
Altcode: 1997fasp.conf..322C
  This is a preliminary report about parallel observations of
  chromospheric and photospheric spectra in the ultraviolet and visible
  spectral regions using SUMER on SOHO and the VTT on Tenerife performed
  begin of September 1996. The aim is to search for relations of vertical
  velocity patterns in the upper photosphere and chromosphere in the
  solar disk center. In addition temporal changes in these parts of the
  solar atmosphere are investigated.

Title: Dynamical Properties of the Chromosphere and Transition Region
in the Supergranular Network: What Precision of the Spectral Line
    Characteristics Can be Reached?
Authors: Curdt, W.; Kucera, A.; Rybák, J.; Schühle, U.; Wöhl, H.
Bibcode: 1997ESASP.404..307C
Altcode: 1997cswn.conf..307C
  No abstract at ADS

Title: Radiometric calibration of the telescope and ultraviolet
    spectrometer SUMER on SOHO
Authors: Hollandt, Jörg; Schühle, Udo; Paustian, Wolfgang; Curdt,
   Werner; Kühne, Michael; Wende, Burkhard; Wilhelm, Klaus
Bibcode: 1996ApOpt..35.5125H
Altcode:
  The prelaunch spectral-sensitivity calibration of the solar spectrometer
  SUMER (Solar Ultraviolet Measurements of Emitted Radiation) is
  described. SUMER is part of the payload of the Solar and Heliospheric
  Observatory (SOHO), which begins its scientific mission in 1996. The
  instrument consists of a telescope and a spectrometer capable of taking
  spatially and spectrally highly resolved images of the Sun in a spectral
  range from 50 to 161 nm. The pointing capabilities, the dynamic range,
  and the sensitivity of the instrument allow measurements both on
  the solar disk and above the limb as great as two solar radii. To
  determine plasma temperatures and densities in the solar atmosphere,
  the instrument needs an absolute spectral-sensitivity calibration. Here
  we describe the prelaunch calibration of the full instrument, which
  utilizes a radiometric transfer-standard source. The transfer standard
  was based on a high-current hollow-cathode discharge source. It
  had been calibrated in the laboratory for vacuum UV radiometry of
  the Physikalisch-Technische Bundesanstalt by use of the calculable
  spectral photon flux of the Berlin electron storage ring for synchrotron
  radiation (BESSY)-a primary radiometric source standard.

Title: A Solar EUV Spectral Atlas Observed with SUMER
Authors: Brekke, P.; Wilhelm, K.; Lemaire, P.; Curdt, W.; Schuhle,
   U.; Poland, A.; Kucera, T.; Hassler, D. M.; Siegmund, O. H. W.
Bibcode: 1996AAS...188.3713B
Altcode: 1996BAAS...28..879B
  We present the first solar EUV spectral atlas in the wavelength range
  500 -- 1600 { Angstroms}. The spectra were recorded with the Solar
  Ultraviolet Measurements of Emitted Radiation (SUMER) which is part
  of the ESA/NASA Solar and Heliospheric Observatory (SOHO). The solar
  spectrum below 1200 { Angstroms} is not very well known. Thus, the
  present spectral atlas, and SUMER observations in general, represents
  a new important diagnostic tool to study essential physical parameters
  of the solar atmosphere. It includes emission from atoms and ions in
  the temperature range 10(4) to 2 x 10(6) K. Thus, emission lines and
  continua emitted from the lower chromosphere to the lower corona
  can be studied. The atlas is also useful as a planning tool for
  SUMER studies to determine useful dwell times, possible blends, and
  to select proper data extraction windows. The angular resolution of
  SUMER is close to 1 arcsec, but the atlas presented here represents an
  average along part of the 1-arcsec wide slit, typically 30 arcsec. The
  spectral resolving power of the instrument is lambda /Delta lambda =
  17770-38300. For more details about the SUMER instrument we refer to
  Wilhelm et al. (Solar Physics, 162, 189, 1995). The spectral data in
  this atlas were obtained with the spectrometer slit positioned at the
  center of the solar disk with a dwell time of 300 s to bring up weak
  lines and continua. The full spectral range was put together from
  a number of exposures each covering approximately 20 { Angstroms}
  in 1st order on the coated, and therefore most sensitive, part (KrB)
  of the detector. 1st and 2nd order spectra are superimposed. The
  spectral atlas is available in a computer readable format together
  with a IDL program to read and display the data using a widget
  interface. The atlas and the programs can be obtained via the World
  Wide Web (http://hydra.mpae.gwdg.de/mpae_projects/SUMER/sumer.html)
  or by contacting one of the authors.

Title: Intercalibration and Co-Registration of the LASCO, UVCS and
    SUMER instruments on SOHO
Authors: Michels, J.; Kohl, J. L.; Noci, G.; Antonucci, E.; Tondello,
   G.; Huber, M. C. E.; Curdt, W.; Hollandt, J.; Lemaire, P.; Schuhle,
   U.; Wilhelm, K.; Korendyke, C.; Moran, T.; Raymond, J. C.; Romoli,
   M.; Benna, C.; Ciaravella, A.; Fineschi, S.; Gardner, L. D.; Giordano,
   S.; Naletto, G.; Nicolosi, P.; Siegmund, O. H. W.; Spadaro, D.; Smith,
   P. L.; Strachan, L.
Bibcode: 1996AAS...188.3706M
Altcode: 1996BAAS...28..878M
  Joint observations of equatorial streamers by three SOHO instruments
  have been used for radiometric intercalibration, co-registration and
  other spectroscopic comparisons. The results are used to track the
  stability of the radiometric calibrations of the Ultraviolet Coronagraph
  Spectrometer (UVCS) and the Solar Ultraviolet Measurements of Emitted
  Radiation (SUMER) experiment at overlapping wavelenghs. Observations
  of equatorial streamers at heliocentric heights from 1.25 to 1.5
  R_⊙ are used for the intercalibrations. The results are compared to
  pre-launch laboratory calibrations and to observations of stars. The
  first stellar observation was for 38 AQI. These UV observations are
  compared to coronal green line (Fe XIV) observations obtained with the
  Large Angle Spectrometric Coronagraph (LASCO) C1 coronagraph obtained
  in the same time frame. Intercomparisons of spectral line profiles
  among LASCO, SUMER, and UVCS are also planned. The LASCO research is
  supported by NASA Grant NDPR S92835D; the UVCS research is supported by
  NASA Contract NAS5-31250 to the Smithsonian Astrophysical Observatory,
  by the Italian Space Agency and by Switzerland, and SUMER is financially
  supported by BMFT/DARA, CNES, NASA and PRODEX (Swiss Contribution).

Title: SUMER - Solar Ultraviolet Measurements of Emitted Radiation
Authors: Wilhelm, K.; Curdt, W.; Marsch, E.; Schühle, U.; Lemaire,
   P.; Gabriel, A.; Vial, J. -C.; Grewing, M.; Huber, M. C. E.; Jordan,
   S. D.; Poland, A. I.; Thomas, R. J.; Kühne, M.; Timothy, J. G.;
   Hassler, D. M.; Siegmund, O. H. W.
Bibcode: 1995SoPh..162..189W
Altcode:
  The instrument SUMER - Solar Ultraviolet Measurements of Emitted
  Radiation is designed to investigate structures and associated dynamical
  processes occurring in the solar atmosphere, from the chromosphere
  through the transition region to the inner corona, over a temperature
  range from 10<SUP>4</SUP> to 2 × 10<SUP>6</SUP>K and above. These
  observations will permit detailed spectroscopic diagnostics of plasma
  densities and temperatures in many solar features, and will support
  penetrating studies of underlying physical processes, including plasma
  flows, turbulence and wave motions, diffusion transport processes,
  events associated with solar magnetic activity, atmospheric heating,
  and solar wind acceleration in the inner corona. Specifically, SUMER
  will measure profiles and intensities of EUV lines; determine Doppler
  shifts and line broadenings with high accuracy; provide stigmatic
  images of the Sun in the EUV with high spatial, spectral, and temporal
  resolution; and obtain monochromatic maps of the full Sun and the inner
  corona or selected areas thereof. SUMER will be flown on the Solar
  and Heliospheric Observatory (SOHO), scheduled for launch in November,
  1995. This paper has been written to familiarize solar physicists with
  SUMER and to demonstrate some command procedures for achieving certain
  scientific observations.

Title: Some design and performance features of SUMER: solar
    ultraviolet measurements of emitted radiation
Authors: Wilhelm, Klaus; Curdt, W.; Marsh, E.; Schuehle, Udo H.;
   Lemaire, Philippe; Gabriel, Alan H.; Vial, J. -C.; Grewing, Michael;
   Huber, Martin C.; Jordan, S. D.; Poland, Arthur I.; Thomas, Roger J.;
   Kuehne, Mikhael; Timothy, J. Gethyn; Hassler, Donald M.; Siegmund,
   Oswald H.
Bibcode: 1995SPIE.2517....2W
Altcode:
  The instrument SUMER (solar ultraviolet measurements of emitted
  radiation) is designed to investigate structures and associated
  dynamical processes occurring in the solar atmosphere from the
  chromosphere through the transition region to the inner corona, over a
  temperature range from 10<SUP>4</SUP> to 2 multiplied by 10<SUP>6</SUP>
  K and above. The observations will be performed, on board SOHO (solar
  and heliospheric observatory) scheduled for launch in November 1995,
  by a scanning, normal-incidence telescope/spectrometer system in
  the wavelength range from 500 to 1610 angstrom. Spatial resolution
  requirements compatible with the pointing stability of SOHO are less
  than 1000 km corresponding to about 1-arcsec angular resolution. Doppler
  observations of EUV line shifts and broadenings should permit solar
  plasma velocity measurements down to 1 km s<SUP>-1</SUP>. We report
  here on some specific features of this instrument related to its
  pointing as well as its spatial and spectral resolution capabilities.

Title: Solar Ultraviolet Measurements of Ultraviolet Radiation
(SUMER) instrument on SOHO: design, performance predictions, and
    calibration aspects
Authors: Schuehle, Udo H.
Bibcode: 1994SPIE.2283...47S
Altcode:
  The solar EUV spectrometer SUMER will operate in the wavelength
  range 500 angstrom to 1600 angstrom on the SOHO spacecraft. It will
  allow measurements of profiles, Doppler shifts, and intensities of
  solar extreme ultraviolet lines. Various mechanisms for pointing and
  focusing of the optical components contribute to the versatility of the
  instrument. The normal incidence optical design of the telescope and
  the spectrometer puts very stringent constraints on the cleanliness of
  the instrument and the mechanical design. The calibration techniques
  used, including imaging tests in the EUV, wavelength, and radiometric
  calibrations are outlined, and performance predictions are given.

Title: 'SUMER' - Solar Ultraviolet Measurements of Emitted Radiation
Authors: Wilhelm, K.; Curdt, W.; Gabriel, A. H.; Grewing, M.; Huber,
   M. C. E.; Jordan, S. D.; Kuhne, M.; Lemaire, P.; Marsch, E.; Poland,
   A. I.; Schuhle, U.; Thomas, R. J.; Timothy, J. G.; Vial, J. -C.
Bibcode: 1994scs..conf..619W
Altcode: 1994IAUCo.144..619W
  SUMER is designed for the investigations of plasma flow characteristics,
  turbulence and wave motions, plasma densities and temperatures,
  structures and events associated with solar magnetic activity in the
  chromosphere, the transition zone and the corona. The spatial and
  spectral resolution capabilities of the instrument are considered in
  some detail, and a new detector concept is introduced.

Title: SUMER - Solar Ultraviolet Measurements of Emitted Radiation
Authors: Wilhelm, K.; Curdt, W.; Marsch, E.; Schuehle, U.; Gabriel,
   A. H.; Lemaire, P.; Vial, J. -C.; Grewing, M.; Huber, M. C. E.;
   Jordan, S. D.; Poland, A. I.; Thomas, R. J.; Kuehne, M.; Timothy, J. G.
Bibcode: 1993BAAS...25.1192W
Altcode:
  No abstract at ADS

Title: The Cleanliness Control Program for SUMER/SOHO
Authors: Schühle, U.
Bibcode: 1993uxrs.conf..373S
Altcode:
  No abstract at ADS

