The Ariel space mission will characterize spectroscopically the atmospheres of a large and diverse sample of hundreds of exoplanets. Through the study of targets with a wide range of planetary parameters (mass, density, equilibrium temperature) and host star types the origin for the diversity observed in known exoplanets will be better understood. Ariel is an ESA Medium class science mission (M4) with a spacecraft bus developed by industry under contract to ESA, and a Payload provided by a consortium of national funding agencies in ESA member states, plus contributions from NASA, the CSA and JAXA. The payload is based on a 1-meter class telescope operated at below 60K, built all in Aluminium, which feeds two science instruments. A multi-channel photometer and low-resolution spectrometer instrument (the FGS, Fine Guidance System instrument) operating from 0.5 – 1.95 microns in wavelength provides both guidance information for stabilizing the spacecraft pointing as well as vital scientific information from spectroscopy in the near-infrared and photometry in the visible channels. The Ariel InfraRed Spectrometer (AIRS) instrument provides medium resolution spectroscopy from 1.95 – 7.8 microns wavelength coverage over two instrument channels. Supporting subsystems provide the necessary mechanical, thermal and electronics support to the cryogenic payload. This paper presents the overall picture of the payload for the Ariel mission. The payload tightly integrates the design and analysis of the various payload elements (including for example the integrated STOP analysis of the Telescope and Common Optics) in order to allow the exacting photometric stability requirements for the mission to be met. The Ariel payload has passed through the Preliminary Design Review (completed in Q2 2023) and is now developing and building prototype models of the Telescope, Instruments and Subsystems (details of which will be provided in other contributions to this conference). This paper will present the current status of the development work and outline the future plans to complete the build and verification of the integrated payload.
Ariel (Atmospheric Remote-Sensing Infrared Exoplanet Large Survey) is the adopted M4 mission in the framework of the ESA “Cosmic Vision” program. Its purpose is to survey the atmospheres of known exoplanets through transit spectroscopy. The launch is scheduled for 2029. The scientific payload consists of an off-axis, unobscured Cassegrain telescope feeding a set of photometers and spectrometers in the waveband 0.5-7.8 µm and operating at cryogenic temperatures (55 K). The Telescope Assembly is based on an innovative fully aluminium design to tolerate thermal variations to avoid impacts on the optical performance; it consists of a primary parabolic mirror with an elliptical aperture of 1.1 m (the major axis), followed by a hyperbolic secondary that is mounted on a refocusing system, a parabolic re-collimating tertiary and a flat folding mirror directing the output beam parallel to the optical bench. An innovative mounting system based on 3 flexure hinges supports the primary mirror on one of the optical bench sides. The instrument bay on the other side of the optical bench houses the Ariel IR Spectrometer (AIRS) and the Fine Guidance System / NIR Spectrometer (FGS/NIRSpec). The Telescope Assembly is in phase B2 towards the Critical Design Review; the fabrication of the structural and engineering models has started; some components, i.e., the primary mirror and its mounting system are undergoing further qualification activities. This paper aims to update the scientific community on the progress concerning the development, manufacturing and qualification activity of the ARIEL Telescope Assembly.
Ariel (Atmospheric Remote-sensing Infrared Exoplanet Large-survey) is an ESA M class mission aimed at the study of exoplanets. The satellite will orbit in the lagrangian point L2 and will survey a sample of 1000 exoplanets simultaneously in visible and infrared wavelengths. The challenging scientific goal of Ariel implies unprecedented engineering efforts to satisfy the severe requirements coming from the science in terms of accuracy. The most important specification – an all-Aluminum telescope – requires very accurate design of the primary mirror (M1), a novel, off-set paraboloid honeycomb mirror with ribs, edge, and reflective surface. To validate such a mirror, some tests were carried out on a prototype – namely Pathfinder Telescope Mirror (PTM) – built specifically for this purpose. These tests, carried out at the Centre Spatial de Liège in Belgium – revealed an unexpected deformation of the reflecting surface exceeding a peek-to-valley of 1µm. Consequently, the test had to be re-run, to identify systematic errors and correct the setting for future tests on the final prototype M1. To avoid the very expensive procedure of developing a new prototype and testing it both at room and cryogenic temperatures, it was decided to carry out some numerical simulations. These analyses allowed first to recognize and understand the reasoning behind the faults occurred during the testing phase, and later to apply the obtained knowledge to a new M1 design to set a defined guideline for future testing campaigns.
Ariel (Atmospheric Remote-Sensing Infrared Exoplanet Large Survey) is the adopted M4 mission in the framework of the ESA “Cosmic Vision” program. Its purpose is to conduct a survey of the atmospheres of known exoplanets through transit spectroscopy. Launch is scheduled for 2029. Ariel scientific payload consists of an off-axis, unobscured Cassegrain telescope feeding a set of photometers and spectrometers in the waveband between 0.5 and 7.8 µm and operating at cryogenic temperatures (55 K). The Telescope Assembly is based on an innovative fully-aluminum design to tolerate thermal variations avoiding impacts on the optical performance; it consists of a primary parabolic mirror with an elliptical aperture of 1.1 m of major axis, followed by a hyperbolic secondary that is mounted on a refocusing system, a parabolic re-collimating tertiary and a flat folding mirror directing the output beam parallel to the optical bench. An innovative mounting system based on 3 flexure-hinges supports the primary mirror on one side of the optical bench. The instrument bay on the other side of the optical bench houses the Ariel IR Spectrometer (AIRS) and the Fine Guidance System / NIR Spectrometer (FGS/NIRSpec). The Telescope Assembly is in phase B2 towards the Preliminary Design Review to start the fabrication of the structural model; some components, i.e., the primary mirror, its mounting system and the refocusing mechanism, are undergoing further development activities to increase their readiness level. This paper describes the design and development of the ARIEL Telescope Assembly.
The Atmospheric Remote-Sensing Infrared Exoplanet Large-survey, ARIEL, has been selected to be the next (M4) medium class space mission in the ESA Cosmic Vision programme. From launch in 2028, and during the following 4 years of operation, ARIEL will perform precise spectroscopy of the atmospheres of ~1000 known transiting exoplanets using its metre-class telescope. A three-band photometer and three spectrometers cover the 0.5 µm to 7.8 µm region of the electromagnetic spectrum.
This paper gives an overview of the mission payload, including the telescope assembly, the FGS (Fine Guidance System) - which provides both pointing information to the spacecraft and scientific photometry and low-resolution spectrometer data, the ARIEL InfraRed Spectrometer (AIRS), and other payload infrastructure such as the warm electronics, structures and cryogenic cooling systems.
Ariel, the “atmospheric remote sensing infrared exoplanet large survey” mission, is the European Space Agency’s Cosmic Vision M4 (medium-class number 4) science mission. It has recently gone through an implementation approval (“adoption”), with a planned launch in 2029. Ariel, together with two other M4 candidate missions (THOR and XIPE), was recommended in June 2015 to enter an assessment study, consisting of a Phase 0 at the ESA internal Concurrent Design Facility study followed by a Phase A with parallel industrial studies. The Phase A was concluded in March 2018 with the selection of Ariel as the M4 mission endorsed by the ESA Science Programme Committee (SPC). Phase B1 was subsequently initiated, and was concluded by the Mission Adoption Review in mid-2020, followed by the formal adoption of Ariel in November 2020 by the SPC. Ariel is a survey-type mission dedicated to the characterisation of exoplanets by performing a chemical census. Using the differential technique of transit/eclipse spectroscopic observations, Ariel will obtain transmission and/or emission spectra of the atmospheres of a large (~1000) and diverse sample of known exoplanets covering a wide range of masses, densities, equilibrium temperatures, orbital properties and host-star characteristics. This will include hot Jupiters to warm Super-Earths, orbiting A to M spectral class host stars. This paper reports on the Ariel Phase 0/A/B1 study, including the conclusions of the reviews that were conducted in 2020 to close the study and support the adoption process.
The Solar Orbiter mission [1],[2],[3], part of the Cosmic Vision Science Program of European Space Agency (ESA), to be launched in 2017, is devoted to the Sun observation. From its unique vantage point in an elliptical orbit around the Sun, and approaching as close as 60 solar radii, Solar Orbiter will provide unprecedented closeup and high-latitude observations of the Sun. The Extreme Ultraviolet Imager (EUI) instrument [4],[5],[6],[7],[8],[9] was selected as one of the 10 scientific payload instruments of the Solar Orbiter mission.
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.
PLATO (PLAnetary Transits and Oscillation of stars) is a medium-class space mission part of the ESA Cosmic vision program. Its goal is to find and study extrasolar planetary systems, emphasizing on planets located in habitable zone around solar-like stars. PLATO is equipped with 26 cameras, operating between 500 and 1000nm. The alignment of the focal plane assembly (FPA) with the optical assembly is a time consuming process, to be performed for each of the 26 cameras. An automatized method has been developed to fasten this process. The principle of the alignment is to illuminate the camera with a collimated beam and to vary the position of the FPA to search for the position which minimizes the RMS spot diameter. To reduce the total number of measurements which is performed, the alignment method is done by iteratively searching for the best focus, decreasing at each step the error on the estimated best focus by a factor 2. Because the spot size at focus is similar to the pixel, it would not be possible with this process alone to reach an alignment accuracy of less than several tens of microns. Dithering, achieved by in-plane translation of the focal plane and image recombination, is thus used to increase the sampling of the spot and decrease the error on the merit function.
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.
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.
The PROBA2 mission has been launched on 2nd November2009 with a Rockot launcher to a Sunsynchronous orbit at an altitude of 725 km. Its nominal operation duration is two years with possible extension of 2 years. PROBA2 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. The mission is tracked by the ESA Redu Mission Operation Center.
The EUV high resolution imager (HRI) channel of the Extreme Ultraviolet Imager (EUI) on-board Solar Orbiter will observe the solar atmospheric layers at 17.4 nm wavelength with a 200 km resolution.
The HRI channel is based on a compact two mirrors off-axis design. The spectral selection is obtained by a multilayer coating deposited on the mirrors and by redundant Aluminum filters rejecting the visible and infrared light. The detector is a 2k x 2k array back-thinned silicon CMOS-APS with 10 μm pixel pitch, sensitive in the EUV wavelength range.
Due to the instrument compactness and the constraints on the optical design, the channel performance is very sensitive to the manufacturing, alignments and settling errors. A trade-off between two optical layouts was therefore performed to select the final optical design and to improve the mirror mounts. The effect of diffraction by the filter mesh support and by the mirror diffusion has been included in the overall error budget. Manufacturing of mirror and mounts has started and will result in thermo-mechanical validation on the EUI instrument structural and thermal model (STM).
Because of the limited channel entrance aperture and consequently the low input flux, the channel performance also relies on the detector EUV sensitivity, readout noise and dynamic range. Based on the characterization of a CMOS-APS back-side detector prototype, showing promising results, the EUI detector has been specified and is under development. These detectors will undergo a qualification program before being tested and integrated on the EUI instrument.
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 (> 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.
J.-P. Halain, P. Rochus, E. Renotte, A. Hermans, L. Jacques, A. Mazzoli, F. Auchère, D. Berghmans, L. Harra, U. Schühle, W. Schmutz, R. Aznar Cuadrado, C. Dumesnil, M. Gyo, T. Kennedy, C. Verbeeck, P. Smith
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.
Etienne Renotte, Andres Alia, Alessandro Bemporad, Joseph Bernier, Cristina Bramanti, Steve Buckley, Gerardo Capobianco, Ileana Cernica, Vladimir Dániel, Radoslav Darakchiev, Marcin Darmetko, Arnaud Debaize, François Denis, Richard Desselle, Lieve de Vos, Adrian Dinescu, Silvano Fineschi, Karl Fleury-Frenette, Mauro Focardi, Aurélie Fumel, Damien Galano, Camille Galy, Jean-Marie Gillis, Tomasz Górski, Estelle Graas, Rafał Graczyk, Konrad Grochowski, Jean-Philippe Halain, Aline Hermans, Russ Howard, Carl Jackson, Emmanuel Janssen, Hubert Kasprzyk, Jacek Kosiec, Serge Koutchmy, Jana Kovačičinová, Nektarios Kranitis, Michał Kurowski, Michał Ładno, Philippe Lamy, Federico Landini, Radek Lapáček, Vít Lédl, Sylvie Liebecq, Davide Loreggia, Brian McGarvey, Giuseppe Massone, Radek Melich, Agnes Mestreau-Garreau, Dominique Mollet, Łukasz Mosdorf, Michał Mosdorf, Mateusz Mroczkowski, Raluca Muller, Gianalfredo Nicolini, Bogdan Nicula, Kevin O'Neill, Piotr Orleański, Marie-Catherine Palau, Maurizio Pancrazzi, Antonios Paschalis, Karel Patočka, Radek Peresty, Irina Popescu, Pavel Psota, Miroslaw Rataj, Jan Rautakoski, Marco Romoli, Roman Rybecký, Lucas Salvador, Jean-Sébastien Servaye, Cornel Solomon, Yvan Stockman, Arkadiusz Swat, Cédric Thizy, Michel Thomé, Kanaris Tsinganos, Jim Van der Meulen, Nico Van Vooren, Tomáš Vit, Tomasz Walczak, Alicja Zarzycka, Joe Zender, Andrei Zhukov
KEYWORDS: Coronagraphy, Sensors, Sun, Solar processes, Field programmable gate arrays, Light emitting diodes, Electronics, Staring arrays, Space operations, Information operations
The “sonic region” of the Sun corona remains extremely difficult to observe with spatial resolution and sensitivity sufficient to understand the fine scale phenomena that govern the quiescent solar corona, as well as phenomena that lead to coronal mass ejections (CMEs), which influence space weather. Improvement on this front requires eclipse-like conditions over long observation times. The space-borne coronagraphs flown so far provided a continuous coverage of the external parts of the corona but their over-occulting system did not permit to analyse the part of the white-light corona where the main coronal mass is concentrated. The proposed PROBA-3 Coronagraph System, also known as ASPIICS (Association of Spacecraft for Polarimetric and Imaging Investigation of the Corona of the Sun), with its novel design, will be the first space coronagraph to cover the range of radial distances between ~1.08 and 3 solar radii where the magnetic field plays a crucial role in the coronal dynamics, thus providing continuous observational conditions very close to those during a total solar eclipse. PROBA-3 is first a mission devoted to the in-orbit demonstration of precise formation flying techniques and technologies for future European missions, which will fly ASPIICS as primary payload. The instrument is distributed over two satellites flying in formation (approx. 150m apart) to form a giant coronagraph capable of producing a nearly perfect eclipse allowing observing the sun corona closer to the rim than ever before. The coronagraph instrument is developed by a large European consortium including about 20 partners from 7 countries under the auspices of the European Space Agency. This paper is reviewing the recent improvements and design updates of the ASPIICS instrument as it is stepping into the detailed design phase.
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.
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.
This paper presents predictions of space radiation parameters for four space instruments performed by the Centre Spatial
de Liège (ULg – Belgium); EUI, the Extreme Ultra-violet Instrument, on-board the Solar Orbiter platform; ESIO,
Extreme-UV solar Imager for Operations, and JUDE, the Jupiter system Ultraviolet Dynamics Experiment, which was
proposed for the JUICE platform.
For Solar Orbiter platform, the radiation environment is defined by ESA environmental specification and the
determination of the parameters is done through ray-trace analyses inside the EUI instrument.
For ESIO instrument, the radiation environment of the geostationary orbit is defined through simulations of the trapped
particles flux, the energetic solar protons flux and the galactic cosmic rays flux, taking the ECSS standard for space
environment as a guideline. Then ray-trace analyses inside the instrument are performed to predict the particles fluxes at
the level of the most radiation-sensitive elements of the instrument.
For JUICE, the spacecraft trajectory is built from ephemeris files provided by ESA and the radiation environment is
modeled through simulations by JOSE (Jovian Specification Environment model) then ray-trace analyses inside the
instrument are performed to predict the particles fluxes at the level of the most radiation-sensitive elements of the
instrument.
PROBA-3 is a mission devoted to the in-orbit demonstration of precise formation flying techniques and technologies for future ESA missions. PROBA-3 will fly ASPIICS (Association de Satellites pour l’Imagerie et l’Interferométrie de la Couronne Solaire) as primary payload, which makes use of the formation flying technique to form a giant coronagraph capable of producing a nearly perfect eclipse allowing to observe the sun corona closer to the rim than ever before. The coronagraph is distributed over two satellites flying in formation (approx. 150m apart). The so called Coronagraph Satellite carries the camera and the so called Occulter Satellite carries the sun occulter disc. This paper is reviewing the design and evolution of the ASPIICS instrument as at the beginning of Phase C/D.
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.
The Extreme Ultraviolet Imager (EUI) on-board the Solar Orbiter mission will provide image sequences of the solar atmosphere at selected spectral emission lines in the extreme and vacuum ultraviolet.
For the two Extreme Ultraviolet (EUV) channels of the EUI instrument, low noise and radiation tolerant detectors with low power consumption and high sensitivity in the 10-40 nm wavelength range are required to achieve the science objectives.
In that frame, a dual-gain 10 μm pixel pitch back-thinned 1k x 1k Active Pixel Sensor (APS) CMOS prototype has been tested during the preliminary development phase of the instrument, to validate the pixel design, the expected EUV sensitivity and noise level, and the capability to withstand the mission radiation environment.
Taking heritage of this prototype, the detector architecture has been improved and scaled up to the required 3k x 3k array. The dynamic range is increased, the readout architecture enhanced, the power consumption reduced, and the pixel design adapted to the required stitching. The detector packaging has also been customized to fit within the constraints imposed by the camera mechanical, thermal and electrical boundaries. The manufacturing process has also been adapted and back-thinning process improved.
Once manufactured and packaged, a batch of sensors will undergo a characterization and calibration campaign to select the best candidates for integration into the instrument qualification and flight cameras.
The flight devices, within their cameras, will then be embarked on the EUI instrument, and be the first scientific APSCMOS detectors for EUV observation of the Sun.
Solar Orbiter EUI instrument was submitted to a high solar flux to correlate the thermal model of the instrument. EUI, the Extreme Ultraviolet Imager, is developed by a European consortium led by the Centre Spatial de Liège for the Solar Orbiter ESA M-class mission. The solar flux that it shall have to withstand will be as high as 13 solar constants when the spacecraft reaches its 0.28AU perihelion. It is essential to verify the thermal design of the instrument, especially the heat evacuation property and to assess the thermo-mechanical behavior of the instrument when submitted to high thermal load. Therefore, a thermal balance test under 13 solar constants was performed on the first model of EUI, the Structural and Thermal Model. The optical analyses and experiments performed to characterize accurately the thermal and divergence parameters of the flux are presented; the set-up of the test, and the correlation with the thermal model performed to deduce the unknown thermal parameters of the instrument and assess its temperature profile under real flight conditions are also presented.
The SoloHI instrument for the ESA/NASA Solar Orbiter mission will track density fluctuations in the inner
heliosphere, by observing visible sunlight scattered by electrons in the solar wind. Fluctuations are associated with
dynamic events such as coronal mass ejections, but also with the “quiescent” solar wind. SoloHI will provide the
crucial link between the low corona observations from the Solar Orbiter instruments and the in-situ measurements
on Solar Orbiter and the Solar Probe Plus missions. The instrument is a visible-light telescope, based on the
SECCHI/Heliospheric Imager (HI) currently flying on the STEREO mission. In this concept, a series of
baffles reduce the scattered light from the solar disk and reflections from the spacecraft to levels below
the scene brightness, typically by a factor of 1012. The fluctuations are imposed against a much brighter
signal produced by light scattered by dust particles (the zodiacal light/F-corona). Multiple images are
obtained over a period of several minutes and are summed on-board to increase the signal-to-noise ratio
and to reduce the telemetry load. SoloHI is a single telescope with a 40⁰ field of view beginning at 5°
from the Sun center. Through a series of Venus gravity assists, the minimum perihelia for Solar Orbiter will
be reduced to about 60 Rsun (0.28 AU), and the inclination of the orbital plane will be increased to a
maximum of 35° after the 7 year mission. The CMOS/APS detector is a mosaic of four 2048 x 1930
pixel arrays, each 2-side buttable with 11 μm pixels.
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.
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.
PROBA-3 is a technology mission devoted to the in-orbit demonstration of formation flying techniques and technologies.
PROBA-3 will implement a giant coronagraph (called ASPIICS) that will both demonstrate and exploit the capabilities
and performances of formation flying. ASPIICS is distributed on two spacecrafts separated by 150m, one hosting the
external occulting disk and the other the optical part of the coronagraph. This part implements a three-mirror-anastigmat
(TMA) telescope. Its pupil is placed about 800mm in front of the primary mirror, a solution allowing an efficient baffling
and a high reduction of the stray light inside the instrument. A complete stray light analysis of the TMA has been carried
out to design the baffles and to establish the required roughness of the mirrors. The analysis has been performed in two
steps: first, by calculating the diffraction pattern behind the occulter due to an extended monochromatic source having
the diameter of the Sun; second, by propagating this diffraction pattern, through all the telescope optical components, to
the prime focal plane. The results obtained are described in this article.
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.
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 Liège (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.
The Heliospheric Imager (HI) is part of the SECCHI suite of instruments on-board the two STEREO observatories
launched in October 2006. The two HI instruments provide stereographic image pairs of solar coronal plasma and
coronal mass ejections (CME) over a field of view ranging from 13 to 330 R0.
The HI instrument is a combination of two refractive optical systems with a two stage multi-vane baffle system. The key
challenge of the instrument design is the rejection of the solar disk light by the front baffle, with total straylight
attenuation at the detector level of the order of 10-13 to 10-15. Optical systems and baffles were designed and tested to
reach the required rejection.
This paper presents the pre-flight optical tests performed under vacuum on the two HI flight models in flight temperature
conditions. These tests included an end-to-end straylight verification of the front baffle efficiency, a co-alignment and an
optical calibration of the optical systems. A comparison of the theoretical predictions of the instrument response and
performance with the calibration results is presented. The instrument in-flight photometric and stray light performance
are also presented and compared with the expected results.
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.
The Heliospheric Imager (HI) forms part of the SECCHI suite of instruments aboard the two NASA STEREO spacecraft
which were launched successfully from Cape Canaveral AFB on 25 Oct 2006 (26 Oct UTC). Following lunar swingby's
on 15 Dec and 21 Jan respectively, the two spacecraft were placed in heliocentric orbits at approximately 1 AU - one
leading and one lagging the Earth, with each spacecraft separating from the Earth by 22.5° per year.
Each HI instrument comprises two wide-angle optical cameras - HI-1 and HI-2 have 20° and 70° fields-of-view which
are off-pointed from the Sun direction by 14.0° and 53.7° respectively, with the optical axes pointed towards the ecliptic
plane. In this way the cameras will for the first time provide stereographic images of the solar corona, and in particular of
Coronal Mass Ejections (CMEs) as they propagate outwards through interplanetary space towards the Earth and beyond.
The wide-field coverage of HI enables imaging of solar ejecta from 15 to about 330 solar radii whilst the other SECCHI
instruments (2 coronagraphs and an EUV imager) provide coverage from the lower corona out to 15 solar radii.
This paper briefly reviews the design and performance requirements for the instrument. The various activation, checkout
and calibration activities before and after opening the instrument's protective cover or door (instrument 'first-light') are
then described and it is shown that the instrument has met the design requirements, including CCD and camera imaging
performance, correction for shutterless operation of the cameras, straylight rejection and thermal requirements. It is
demonstrated from observations of a CME event on 24-25 Jan 2007 that the instrument is capable of detecting CMEs at
an intensity of 1% of the coronal background. Lessons learnt during the design, development and in-orbit operation of
the instrument are discussed.
The Heliospheric Imager (HI) is part of the SECCHI suite of instruments on-board the two STEREO spacecrafts to be launched in 2006. Located on two different orbits, the two HI instruments will provide stereographic images of solar coronal plasma and coronal mass ejections (CME) over a wide field of view (~90°), ranging from 13 to 330 solar radii (R0). These observations complete the 15 R0 field of view of the solar corona obtained with the other SECCHI instruments (2 coronagraphs and an EUV imager).
The HI instrument is a combination of 2 refractive optical systems with 2 different multi-vanes baffle system. The key challenge of the instrument design is the rejection of the solar disk light, with total straylight attenuation of the order of 10-13 to 10-15. The optics and baffles have been specifically designed to reach the required rejection.
This paper presents the SECCHI/HI opto-mechanical design, with the achieved performances. A test program has been run on one flight unit, including vacuum straylight verification test, thermo-optical performance test and co-alignment test. The results are presented and compared with the initial specifications.
The MAGRITTE telescopes are part of the SHARPP instrument suite, part of the Solar Dynamics Observatory (SDO), a NASA spacecraft to be launched in a geostationnary orbit in 2007. The MAGRITTE instrument package will provide high resolution images of the solar corona at high temporal frequency simultaneously in 5 EUV and in Ly-α narrow bandpasses. The 1.4 R0 MAGRITTE common field of view complements the other SHARPP instruments, as well as its spectral coverage with 6 narrow bandpasses located within the 19.5 to 120 nm interval. The key challenges of the MAGRITTE instrument are a high angular resolution (0.66 arcsec/pixel) with a high responsivity (exposure times smaller than 8 sec), combined with restricted spacecraft resources. The design of MAGRITTE is based on a high performance off-axis Ritchey-Chretien optical system combined with a large detector (4 K x 4 K, 12 µm pixel). The tight pointing stability performance of 1.2 arcsec over the image exposure time requires an active image motion control, using pointing information of a Guide Telescope, to compensate low frequency boresight variations produced by spacecraft jitter. The thermomechanical design and the mirror polishing are highly critical issues in the instrument design. This paper presents the MAGRITTE design concept with the expected performances based on a realistic error budget. The mirror polishing concept and performances are discussed.
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.
The Heliospheric Imager (HI) is part of the SECCHI suite of instruments on-board the two STEREO spacecrafts to be launched in 2005. The two HI instruments will provide stereographic image pairs of solar coronal plasma and coronal mass ejections (CME) over a wide field of view (~90°), ranging from 13 to 330 R0. These observations compliment the 15 R0 field of view of the solar corona obtained by the other SECCHI instruments (2 coronagraphs and an EUV imager).
The key challenge of the instrument design is the rejection of the solar disk light, with total straylight attenuation of the order of 10-13 to 10-15. A multi-vane diffractive baffle system has been theoretically optimized to achieve the lower requirement (10-13 for HI-1) and is combined with a secondary baffling system to reach the 10-15 rejection performance in the second camera system (HI-2).
This paper presents the last updates of the SECCHI/HI design concept, with the expected performance. A verification program is currently in progress. The on-going stray-light verification tests are discussed. A set of tests has been conducted in air, and under vacuum. The results are presented and compared with the expected theoretical data.
The Heliospheric Imager (HI) is part of the SECCHI suite of instruments on-board the two STEREO spacecrafts to be launched in 2005. The two HI instruments will provide stereographic image pairs of solar coronal plasma and address the observational problem of very faint coronal mass ejections (CME) over a wide field of view (~90 degree(s)) ranging from 13 to 330 R0. The key element of the instrument design is to reject the solar disk light, with straylight attenuation of the order of 10-13 to 10-15 in the camera systems. This attenuation is accomplished by a specific design of straylight baffling system, and two separate observing cameras with complimentary FOV's cover the wide FOV. A multi-vane diffractive system has been theoretically optimized to achieve the lower requirement (10-13 for HI-1) and is combined with a secondary baffling system to reach the 10-15 rejection performance in the second camera system (HI-2). This paper presents the design concept of the HI optics and baffles, and the preparation of verification tests that will demonstrate the instrument straylight performances. The baffle design has been optimized according to accommodation constrains on the spacecraft, and the optics were studied to provide adequate light gathering power and image quality. Straylight has been studied in the complete configuration, including the lens barrels and the focal plane assemblies. A specific testing facility is currently being studied to characterize the effective straylight rejection of the HI baffling. An overview of the developments for those tests is presented.
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