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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 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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See detailThe Lyman-alpha telescope of the extreme ultraviolet imager on Solar Orbiter
Schühle, Udo; Halain, Jean-Philippe ULg; Meining, Stefan et al

in Proceedings of SPIE (2011), 8148

On the Solar Orbiter mission, the Extreme Ultraviolet Imager (EUI) set of filtergraph-telescopes consists of two high-resolution imagers (HRI) and one dual-band full Sun imager (FSI) that will provide ... [more ▼]

On the Solar Orbiter mission, the Extreme Ultraviolet Imager (EUI) set of filtergraph-telescopes consists of two high-resolution 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 one 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. [less ▲]

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See detailIN-FLIGHT PERFORMANCE OF THE SOLAR UV RADIOMETER LYRA / PROBA-2
Stockman, Yvan ULg; Defise, Jean-Marc ULg; Halain, Jean-Philippe ULg et al

(2010, October 05)

LYRA is a solar radiometer, part of the PROBA-2 micro-satellite payload. The PROBA-2 mission has been launched on 02 November 2009 with a Rockot launcher to a Sun-synchronous orbit at an altitude of 725 ... [more ▼]

LYRA is a solar radiometer, part of the PROBA-2 micro-satellite payload. The PROBA-2 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. LYRA monitors the solar irradiance at a high cadence (> 20Hz) 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. LYRA benefits from wide bandgap detectors based on diamond. It is the first space assessment of these revolutionary UV detectors for astrophysics. [less ▲]

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See detailThe technical challenges of the Solar-Orbiter EUI instrument
Halain, Jean-Philippe ULg; Rochus, Pierre ULg; Renotte, Etienne ULg et al

in Proceedings - Society of Photo-Optical Instrumentation Engineers (2010), 7732(26),

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 ... [more ▼]

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. [less ▲]

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See detailFirst light of SWAP on-board PROBA2
Halain, Jean-Philippe ULg; Defise, Jean-Marc ULg; Rochus, Pierre ULg et al

in Proceedings of SPIE (2010), 7732

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 ... [more ▼]

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 PTB-Bessy 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. [less ▲]

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See detailStray light analysis and optimization of the ASPIICS/PROBA-3 Formation Flying solar coronagraph
Mazzoli, Alexandra ULg; Landini, Federico; Vivès, Sébastien et al

in SPIE, Space Telescopes and Instrumentation 2010 : Optical, Infrared and Millimeter Wave (San Diego, 27 juin-2 juillet) (2010)

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 ... [more ▼]

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. [less ▲]

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See detailThe Heliospheric Imagers Onboard the STEREO Mission
Eyles, C. J.; Harrison, R. A.; Davis, C. et al

in Solar Physics (2009), 254

Mounted on the sides of two widely separated spacecraft, the two Heliospheric Imager (HI) instruments onboard NASA's STEREO mission view, for the first time, the space between the Sun and Earth. These ... [more ▼]

Mounted on the sides of two widely separated spacecraft, the two Heliospheric Imager (HI) instruments onboard NASA's STEREO mission view, for the first time, the space between the Sun and Earth. These instruments are wide-angle visible-light imagers that incorporate sufficient baffling to eliminate scattered light to the extent that the passage of solar coronal mass ejections (CMEs) through the heliosphere can be detected. Each HI instrument comprises two cameras, HI-1 and HI-2, which have 20° and 70° fields of view and are off-pointed from the Sun direction by 14.0° and 53.7°, respectively, with their optical axes aligned in the ecliptic plane. This arrangement provides coverage over solar elongation angles from 4.0° to 88.7° at the viewpoints of the two spacecraft, thereby allowing the observation of Earth-directed CMEs along the Sun -- Earth line to the vicinity of the Earth and beyond. Given the two separated platforms, this also presents the first opportunity to view the structure and evolution of CMEs in three dimensions. The STEREO spacecraft were launched from Cape Canaveral Air Force Base in late October 2006, and the HI instruments have been performing scientific observations since early 2007. The design, development, manufacture, and calibration of these unique instruments are reviewed in this paper. Mission operations, including the initial commissioning phase and the science operations phase, are described. Data processing and analysis procedures are briefly discussed, and ground-test results and in-orbit observations are used to demonstrate that the performance of the instruments meets the original scientific requirements. [less ▲]

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See detailThe DynaMICCS perspective. A mission for a complete and continuous view of the Sun dedicated to magnetism, space weather and space climate
Turck-Chièze, S.; Lamy, P.; Carr, C. et al

in Experimental Astronomy (2009), 23

The DynaMICCS mission is designed to probe and understand the dynamics of crucial regions of the Sun that determine solar variability, including the previously unexplored inner core, the radiative ... [more ▼]

The DynaMICCS mission is designed to probe and understand the dynamics of crucial regions of the Sun that determine solar variability, including the previously unexplored inner core, the radiative/convective zone interface layers, the photosphere/chromosphere layers and the low corona. The mission delivers data and knowledge that no other known mission provides for understanding space weather and space climate and for advancing stellar physics (internal dynamics) and fundamental physics (neutrino properties, atomic physics, gravitational moments...). The science objectives are achieved using Doppler and magnetic measurements of the solar surface, helioseismic and coronographic measurements, solar irradiance at different wavelengths and in-situ measurements of plasma/energetic particles/magnetic fields. The DynaMICCS payload uses an original concept studied by Thalès Alenia Space in the framework of the CNES call for formation flying missions: an external occultation of the solar light is obtained by putting an occulter spacecraft 150 m (or more) in front of a second spacecraft. The occulter spacecraft, a LEO platform of the mini sat class, e.g. PROTEUS, type carries the helioseismic and irradiance instruments and the formation flying technologies. The latter spacecraft of the same type carries a visible and infrared coronagraph for a unique observation of the solar corona and instrumentation for the study of the solar wind and imagers. This mission must guarantee long (one 11-year solar cycle) and continuous observations (duty cycle > 94%) of signals that can be very weak (the gravity mode detection supposes the measurement of velocity smaller than 1 mm/s). This assumes no interruption in observation and very stable thermal conditions. The preferred orbit therefore is the L1 orbit, which fits these requirements very well and is also an attractive environment for the spacecraft due to its low radiation and low perturbation (solar pressure) environment. This mission is secured by instrumental R and D activities during the present and coming years. Some prototypes of different instruments are already built (GOLFNG, SDM) and the performances will be checked before launch on the ground or in space through planned missions of CNES and PROBA ESA missions (PICARD, LYRA, maybe ASPIICS). [less ▲]

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See detailTHE EXTREME ULTRAVIOLET IMAGER (EUI) ONBOARD THE SOLAR ORBITER MISSION
Rochus, Pierre ULg; Halain, Jean-Philippe ULg; Renotte, Etienne ULg et al

in A3. 4. Space-based Astronomy (2009)

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See detailSun Earth Connection Coronal and Heliospheric Investigation (SECCHI)
Howard, R. A.; Moses, J. D.; Vourlidas, A. et al

in Space Science Reviews (2008), 136

The Sun Earth Connection Coronal and Heliospheric Investigation (SECCHI) is a five telescope package, which has been developed for the Solar Terrestrial Relation Observatory (STEREO) mission by the Naval ... [more ▼]

The Sun Earth Connection Coronal and Heliospheric Investigation (SECCHI) is a five telescope package, which has been developed for the Solar Terrestrial Relation Observatory (STEREO) mission by the Naval Research Laboratory (USA), the Lockheed Solar and Astrophysics Laboratory (USA), the Goddard Space Flight Center (USA), the University of Birmingham (UK), the Rutherford Appleton Laboratory (UK), the Max Planck Institute for Solar System Research (Germany), the Centre Spatiale de Leige (Belgium), the Institut d'Optique (France) and the Institut d'Astrophysique Spatiale (France). SECCHI comprises five telescopes, which together image the solar corona from the solar disk to beyond 1 AU. These telescopes are: an extreme ultraviolet imager (EUVI: 1 1.7 R[SUB]o[/SUB]), two traditional Lyot coronagraphs (COR1: 1.5 4 R[SUB]o[/SUB] and COR2: 2.5 15 R[SUB]o[/SUB]) and two new designs of heliospheric imagers (HI-1: 15 84 R[SUB]o[/SUB] and HI-2: 66 318 R[SUB]o[/SUB]). All the instruments use 2048×2048 pixel CCD arrays in a backside-in mode. The EUVI backside surface has been specially processed for EUV sensitivity, while the others have an anti-reflection coating applied. A multi-tasking operating system, running on a PowerPC CPU, receives commands from the spacecraft, controls the instrument operations, acquires the images and compresses them for downlink through the main science channel (at compression factors typically up to 20×) and also through a low bandwidth channel to be used for space weather forecasting (at compression factors up to 200×). An image compression factor of about 10× enable the collection of images at the rate of about one every 2 3 minutes. Identical instruments, except for different sizes of occulters, are included on the STEREO-A and STEREO-B spacecraft. [less ▲]

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See detailCMOS-APS Detectors for Solar Physics: Lessons Learned during the SWAP Preflight Calibration
De Groof, Anik; Berghmans, David; Nicula, Bogdan et al

in Solar Physics (2008)

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See detailSWAP: a novel EUV telescope for space weather
Defise, Jean-Marc ULg; Halain, Jean-Philippe ULg; Berghmans, David et al

in Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series (2007, September 01)

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 ... [more ▼]

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. [less ▲]

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See detailSTEREO: Heliospheric Imager design, pre-flight, and in-flight response comparison
Halain, Jean-Philippe ULg; Mazy, Emmanuel ULg; Defise, Jean-Marc ULg et al

in Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series (2007, September 01)

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 ... [more ▼]

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 R[SUB]0[/SUB]. 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[SUP]-13[/SUP] to 10[SUP]-15[/SUP]. 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. [less ▲]

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See detailIn-orbit verification, calibration, and performance of the Heliospheric Imager on the STEREO mission
Eyles, Chris; Davis, Chris; Harrison, Richard et al

in Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series (2007)

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 ... [more ▼]

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. [less ▲]

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