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See detailDesign status of ASPIICS, an externally occulted coronagraph for PROBA-3
Renotte, Etienne ULg; Alia, A.; Bemporad, A. et al

in Proc. SPIE Volume 9604 Solar Physics and Space Weather Instrumentation VI (2015, September 21)

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 ... [more ▼]

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 ~1.15 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. [less ▲]

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See detailThermal Balance Test of Solar Orbiter EUI Instrument Structural and Thermal Model with 13 Solar Constants
Jacques, Lionel ULg; Halain, Jean-Philippe ULg; Rossi, Laurence ULg et al

Scientific conference (2015, March 26)

Developed by a European consortium led by the Centre Spatial de Liège in Belgium, the Extreme Ultraviolet Imager (EUI) is an instrument onboard the Solar Orbiter ESA M-class mission. At its 0.28AU ... [more ▼]

Developed by a European consortium led by the Centre Spatial de Liège in Belgium, the Extreme Ultraviolet Imager (EUI) is an instrument onboard the Solar Orbiter ESA M-class mission. At its 0.28AU perihelion, the spacecraft will be exposed to a 13 solar constants solar flux. EUI is protected behind the spacecraft heat shield but for three apertures for its telescopes looking at the Sun in the Extreme-UV. To better reject the unwanted visible light and protect 150nm thick EUV filters, Aluminum coated carbon-fiber-reinforced plastics entrance baffles are located at the front of the instrument. The residual absorbed heat by the entrance filters and baffles is evacuated through heat pipes to a dedicated spacecraft thermal interface. To verify its thermal design, the instrument structural and thermal model has been tested in a vacuum chamber with a solar simulator providing the 13 solar constants solar flux at the three entrance apertures and dedicated heaters to model the spacecraft heat shield feedthroughs. To assess the off-pointing performance of the entrance baffles, the instrument was mounted onto a rotating structure inside the chamber. The test setup, results and the thermal model correlation will be presented as well as the calibration of the solar simulator divergence and intensity. [less ▲]

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See detailThe extreme UV imager telescope on-board the Solar Orbiter mission: overview of phase C and D
Halain, Jean-Philippe ULg; Rochus, Pierre ULg; Renotte, Etienne ULg et al

in SPIE Optical Engineering+ Applications (2015)

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 ... [more ▼]

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 thermo-mechanical 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. [less ▲]

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See detailThe extreme ultraviolet imager of solar orbiter: optical design and alignment scheme
Halain, Jean-Philippe ULg; Mazzoli, Alexandra ULg; Meining, S. et al

in SPIE Optical Engineering+ Applications (2015)

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See detailNew Monolithic High Solar Rejection EUV Transmission Filter
Fleury-Frenette, Karl ULg; Renotte, Etienne ULg; Lenaerts, Cedric ULg et al

Conference (2014, August)

New Monolithic High Solar Rejection EUV Transmission Filter Fleury-Frenette, Karl; Renotte, Etienne; Lenaerts, C.; Rossi, Laurence; Jacques, Lionel; Halain, Jean-Philippe; Rochus, Pierre 40th COSPAR ... [more ▼]

New Monolithic High Solar Rejection EUV Transmission Filter Fleury-Frenette, Karl; Renotte, Etienne; Lenaerts, C.; Rossi, Laurence; Jacques, Lionel; Halain, Jean-Philippe; Rochus, Pierre 40th COSPAR Scientific Assembly. Held 2-10 August 2014, in Moscow, Russia, Abstract D2.3-22-14. A new high solar rejection transmission filter for the extreme UV has been developed for the Solar Orbiter Extreme Ultraviolet Imager (EUI). To provide enhanced resilience to high thermal load, a monolithic architecture approach has been taken in order to limit the thermal contact resistance between the filtering sub-micron thin film, its supporting mesh, and holding frame. Some aspects of the manufacturing process involving thin film deposition and photolithography will be presented along with optical performance and space environmental test results. New avenues for improving the thermo-optical properties of the filter will also be discussed. [less ▲]

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See detailSpace radiation parameters for EUI and the Sun Sensor of Solar Orbiter, ESIO and JUDE instruments
Rossi, Laurence ULg; Jacques, Lionel ULg; Halain, Jean-Philippe ULg et al

in Proceedings of SPIE (2014, June 18)

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 ... [more ▼]

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. [less ▲]

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See detailSolar simulation test up to 13 solar constants for the thermal balance of the Solar Orbiter EUI instrument
Rossi, Laurence ULg; zhukova, Maria; Jacques, Lionel ULg et al

in Proceedings of SPIE (2014, June 18)

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 ... [more ▼]

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. [less ▲]

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See detailASPIICS: an externally occulted coronagraph for PROBA-3.Design evolution.
Renotte, Etienne ULg; Carmen Baston, Elena; Bemporad, Alessandro et al

in SPIE 9143, Space Telescopes and Instrumentation 2014: Optical, Infrared, and Millimeter Wave (2014)

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 ... [more ▼]

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. [less ▲]

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See detailThe Extreme UV Imager of Solar Orbiter – From detailed design to Flight Model
Halain, Jean-Philippe ULg; Rochus, Pierre ULg; Renotte, Etienne ULg et al

in Proceedings of SPIE (2014), 9144

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 ... [more ▼]

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. [less ▲]

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See detailThe dual-gain 10 µm back-thinned 3k x 3k CMOS-APS detector of the Solar Orbiter Extreme UV Imager
Halain, Jean-Philippe ULg; Debaize, Arnaud ULg; Gillis, Jean-Marie ULg et al

in Proceedings of SPIE (2014), 9144

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 ... [more ▼]

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 APS-CMOS detectors for EUV observation of the Sun. [less ▲]

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See detailThe solar orbiter imager (SoloHI) instrument for the Solar Orbiter mission
Howard, R. A.; Vourlidas, A.; Korendyke, C. M. et al

in Proceedings of SPIE - The International Society for Optical Engineering (2013)

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 ... [more ▼]

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. [less ▲]

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See detailOn-Orbit Degradation of Solar Instruments
BenMoussa, A.; Gissot, S.; Schühle, U. et al

in Solar Physics (2013)

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 ... [more ▼]

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. [less ▲]

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See detailThe SWAP EUV Imaging Telescope. Part II: In-flight Performance and Calibration
Halain, Jean-Philippe ULg; Berghmans, David; Seaton, Dan et al

in Solar Physics (2013), 286

The Sun Watcher with Active Pixel System detector and Image Processing (SWAP) telescope was launched on 2 November 2009 onboard the ESA PROBA2 technological mission and has acquired images of the solar ... [more ▼]

The Sun Watcher with Active Pixel System detector and Image Processing (SWAP) telescope was launched on 2 November 2009 onboard the ESA PROBA2 technological mission and has acquired images of the solar corona every one to two minutes for more than two years. The most important technological developments included in SWAP are a radiation-resistant CMOS-APS detector and a novel onboard data-prioritization scheme. Although such detectors have been used previously in space, they have never been used for long-term scientific observations on orbit. Thus SWAP requires a careful calibration to guarantee the science return of the instrument. Since launch we have regularly monitored the evolution of SWAP’s detector response in-flight to characterize both its performance and degradation over the course of the mission. These measurements are also used to reduce detector noise in calibrated images (by subtracting dark-current). Because accurate measurements of detector dark-current require large telescope off-points, we also monitored straylight levels in the instrument to ensure that these calibration measurements are not contaminated by residual signal from the Sun. Here we present the results of these tests and examine the variation of instrumental response and noise as a function of both time and temperature throughout the mission. [less ▲]

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See detailThe SWAP EUV Imaging Telescope Part I: Instrument Overview and Pre-Flight Testing
Seaton, Daniel; Berghmans, David; Nicula, Bogdan et al

in Solar Physics (2013), 286

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 ... [more ▼]

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-weatherrelevant 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. [less ▲]

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See detailDiffractive straylight rejection system for wide field imagers. Design, performance and application to the STEREO solar space mission.
Halain, Jean-Philippe ULg

Doctoral thesis (2012)

Space-born wide field imagers have become a new tool used in the frame of Solar Physics and in particular in the field of Space Weather. One particular application is the tracking of coronal mass ejection ... [more ▼]

Space-born wide field imagers have become a new tool used in the frame of Solar Physics and in particular in the field of Space Weather. One particular application is the tracking of coronal mass ejection (CME), generated by violent eruptions on the sun’s surface, that propagates in the heliosphere. The CME brightness however rapidly decreases with the distance from the Sun. To reach a sufficient signal to noise ratio and follow CME away from the Sun, a high sensitivity is therefore required and the unwanted parasitic light (so called straylight) must be minimized. In particular, the Sun disk brightness must be occulted by a highly rejecting baffle system. A multi-edge diffractive baffle can provide a very high level of straylight attenuation for nearly collimated light source. A model of the multi-edge diffractive rejection has been implemented on the basis of the Fresnel diffraction theory. It allows the design and optimisation of such diffractive baffle as function of the instrument and observing geometries. The model was validated on a diffractive baffle mock-up, providing rejection down to an un-precedent level of 10-10 of the input flux. The model of multi-edge diffractive baffle has been applied to the specific configuration of the Heliospheric Imager (HI), on-board the NASA scientific Solar Terrestrial Relations Observatory (STEREO) mission, as part of its overall straylight reduction. The STEREO-HI baffle performance has been validated on a prototype and during the final end-to-end calibration of the flight instrument. After launch, the in-flight straylight level has been quantified, showing a very good correspondence with the on-ground measurements. The straylight evolution has also been shown to be stable during the mission, showing the baffle efficiency does not degrade with the space environment. The STEREO-HI instrument achieves a 10-13 rejection level, or greater, of the solar brightness at the detector pixel level. This instrument is the first wide field space imager viewing from outside the Sun-Earth line, and therefore able to directly follow the propagation of CME from the Sun to the Earth with a high accuracy and sensitivity. Since its launch, it provides unprecedented images and information on solar wind and CME propagation and evolution in the heliosphere. The next generation of wide-field solar imagers are under development for the ESA Solar Orbiter and NASA Solar Probe Plus missions. Their concept benefits from of the STEREO-HI front diffractive baffle system and is based on a multi-edge diffractive baffle to protect their cameras from solar disk brightness. The straylight calibration of these two instruments is in preparation and will be performed at the Centre Spatial de Liège with the tools and methods developed in the frame of the present work. [less ▲]

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See detailEUV high resolution imager on-board Solar Orbiter: optical design and detector performances.
Halain, Jean-Philippe ULg; Mazzoli, Alexandra ULg; Rochus, Pierre ULg et al

Poster (2012, October)

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 ... [more ▼]

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. [less ▲]

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See detailThe EUI instrument on board the Solar Orbiter mission: from breadboard and prototypes to instrument model validation
Halain, Jean-Philippe ULg; Rochus, Pierre ULg; Renotte, Etienne ULg et al

in Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series (2012, June)

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 ... [more ▼]

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. [less ▲]

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See detailUltrathin EUV Filters Testing and Characterization under High Flux (13 SC) for Solar Orbiter EUI Instrument
Jacques, Lionel ULg; Halain, Jean-Philippe ULg; Rossi, Laurence ULg et al

Conference (2011, October 07)

The test setup and characterization parameters of ultrathin EUV filters under high solar flux are presented. These 150nm thick aluminium filters are used at the entrance of the Extreme Ultraviolet Imager ... [more ▼]

The test setup and characterization parameters of ultrathin EUV filters under high solar flux are presented. These 150nm thick aluminium filters are used at the entrance of the Extreme Ultraviolet Imager (EUI) payload, which is developed at the Centre Spatial de Liège for the Solar Orbiter ESA M-class mission. The solar flux that they shall have to withstand will be as high as 13 solar constants when the spacecraft reach its 0.28AU perihelion. A specific design based on additional ribs has therefore been developed to enhance the thermal behaviour and heat evacuation while preserving its optical properties. It is essential to assess the design performances under the Solar Orbiter high solar flux. Therefore, thermal vacuum test under 13 solar constants will be performed. The filters temperature profiles will be measured during the tests through infrared imaging. A thermal correlation of the test will then be performed to deduce the filters actual thermal properties to be used in the global instrument geometrical and thermal mathematical models. [less ▲]

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See detailStraylight-Rejection Performance of the STEREO HI Instruments
Halain, Jean-Philippe ULg; Rochus, Pierre ULg; Defise, Jean-Marc ULg et al

in Solar Physics (2011)

The SECCHI Heliospheric Imager (HI) instruments on-board the STEREO spacecraft have been collecting images of solar wind transients, including coronal mass ejections, as they propagate through the inner ... [more ▼]

The SECCHI Heliospheric Imager (HI) instruments on-board the STEREO spacecraft have been collecting images of solar wind transients, including coronal mass ejections, as they propagate through the inner heliosphere since the beginning of 2007. The scientific use of the images depends critically on the performance of the instruments and its evolution over time. One of the most important factors affecting the performance of the instrument is the rejection of straylight from the Sun and from other bright objects located both within and outside the HI fields of view. This paper presents an analysis of the evolution of the straylight-rejection performance of the HI instrument on each of the two STEREO spacecraft over the three first years of the mission. The straylight level has been evaluated and expressed in mean solar brightness units, in which such scientific observations are usually quoted, using photometric conversion factors. [less ▲]

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See detailFilter failure analysis for the SWAP instrument on-board of PROBA2
Jonckheere, Stijn; Bergen, Bart; Halain, Jean-Philippe ULg et al

in COMPDYN (2011, May)

During its intensive testing campaign, SWAP (Sun Watcher using Active Pixel System detector and image Processing), an optical instrument developed by Centre Spatiale de Liege (CSL) and mounted onto the ... [more ▼]

During its intensive testing campaign, SWAP (Sun Watcher using Active Pixel System detector and image Processing), an optical instrument developed by Centre Spatiale de Liege (CSL) and mounted onto the Belgian satellite PROBA2, was subjected to a multitude of load cases to verify the integrity of the instrument during and after the launch and during the operational phase. The front and rear filters of SWAP, 200 nm thin films, survived intensive vibration tests on the qualification model and acceptance tests on the flight model, both at an instrument level. During the acoustic test on the spacecraft, the front filter exploded while the rear one was undamaged. A new, strengthened filter, coated with a very fine metal mesh was mounted in the instrument. However, this new filter has less good optical properties due to optical diffraction. Therefore a profound analysis of the filter failure is necessary to provide the best possible optical accuracy for future missions with similar equipment. Three load cases are further studied in this paper: the acceleration of the rocket, the instrument depressurisation and the vibro-acoustic behaviour under the large sound and vibration levels. The acceleration and depressurisation are studied together in a two-level computational fluid dynamics (CFD) analysis to assess the effect of the venting of the instrument on the differential pressure over the filter. The main focus of this paper is on a numerical vibro-acoustic analysis, following the procedures used by CSL and ESTEC (European Space Research and Technology Centre). This analysis needs special attention because of the presence of a stochastic excitation (diffuse field) and the very nonlinear behaviour of the filter itself due to its small thickness. Also, an additional postprocessing step based on filter displacements, rather than differential pressure, as done in the ESTEC procedure, is discussed. [less ▲]

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