References of "Mazzoli, Alexandra"
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See detailDevelopment of VUV multilayer coatings for SMILE-UVI instrument
Loicq, Jerôme ULiege; Fleury-Frenette, Karl ULiege; Blain, Pascal ULiege et al

in International Conference on Space Optics — ICSO 2018 (2019, July 12)

he Ultraviolet Imager (UVI) instrument is a very challenging imager developed in the frame of the SMILE-ESA mission. The UV camera will consist of a single imaging system targeted at a portion of the ... [more ▼]

he Ultraviolet Imager (UVI) instrument is a very challenging imager developed in the frame of the SMILE-ESA mission. The UV camera will consist of a single imaging system targeted at a portion of the Lyman-Birge-Hopfield (LBH) N2 wavelength band. The baseline design of the imager meets the requirements to record snapshots of auroral dynamics with sufficient spatial resolution to measure cusp processes (100 km) under fully sunlit conditions from the specified apogee of the spacecraft. To achieve this goal, the UVI instrument utilizes a combination of four on-axis mirrors with an intensified FUV CMOS based camera. The mirrors will be coated with spectral selective interferometric layers to provide most of the signal filtering. The objective of these filters is to select the scientific waveband between 160 and 180 nm. The combined four mirrors have to give an out-of-band rejection ratio as high as possible to reject light from solar diffusion, dayglow and unwanted atomic lines in a range of 10-8 – 10-9. Different multilayer coatings are considered and optimized according to the π- multilayer equation for different H/L ratio and for different angles of incidence. Our theoretical evaluation shows a least a modification of the reflectance spectrum as a function of the angle of incidence, so that the optical beams hitting the different mirrors can have different optical properties depending on the optical fields and the distribution of the rays on the pupil. In this paper the effect of fields and coating homogeneity on the spectral throughput of the UVI instrument will be assessed and described. [less ▲]

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See detailWater Vapor Vertical Profiles on Mars in Dust Storms Observed by TGO/NOMAD
Aoki, Shohei ULiege; Vandaele, A. C.; Daerden, F. et al

in Journal of Geophysical Research: Planets (2019), 124(12), 3482-3497

It has been suggested that dust storms efficiently transport water vapor from the near-surface to the middle atmosphere on Mars. Knowledge of the water vapor vertical profile during dust storms is ... [more ▼]

It has been suggested that dust storms efficiently transport water vapor from the near-surface to the middle atmosphere on Mars. Knowledge of the water vapor vertical profile during dust storms is important to understand water escape. During Martian Year 34, two dust storms occurred on Mars: a global dust storm (June to mid-September 2018) and a regional storm (January 2019). Here we present water vapor vertical profiles in the periods of the two dust storms (Ls = 162–260° and Ls = 298–345°) from the solar occultation measurements by Nadir and Occultation for Mars Discovery (NOMAD) onboard ExoMars Trace Gas Orbiter (TGO). We show a significant increase of water vapor abundance in the middle atmosphere (40–100 km) during the global dust storm. The water enhancement rapidly occurs following the onset of the storm (Ls~190°) and has a peak at the most active period (Ls~200°). Water vapor reaches very high altitudes (up to 100 km) with a volume mixing ratio of ~50 ppm. The water vapor abundance in the middle atmosphere shows high values consistently at 60°S-60°N at the growth phase of the dust storm (Ls = 195°–220°), and peaks at latitudes greater than 60°S at the decay phase (Ls = 220°–260°). This is explained by the seasonal change of meridional circulation: from equinoctial Hadley circulation (two cells) to the solstitial one (a single pole-to-pole cell). We also find a conspicuous increase of water vapor density in the middle atmosphere at the period of the regional dust storm (Ls = 322–327°), in particular at latitudes greater than 60°S. [less ▲]

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See detailMethane on Mars: New insights into the sensitivity of CH 4 with the NOMAD/ExoMars spectrometer through its first in-flight calibration
Liuzzi, G.; Villanueva, G. L.; Mumma, M. J. et al

in Icarus (2019), 321

The Nadir and Occultation for MArs Discovery instrument (NOMAD), onboard the ExoMars Trace Gas Orbiter (TGO) spacecraft was conceived to observe Mars in solar occultation, nadir, and limb geometries, and ... [more ▼]

The Nadir and Occultation for MArs Discovery instrument (NOMAD), onboard the ExoMars Trace Gas Orbiter (TGO) spacecraft was conceived to observe Mars in solar occultation, nadir, and limb geometries, and will be able to produce an outstanding amount of diverse data, mostly focused on properties of the atmosphere. The infrared channels of the instrument operate by combining an echelle grating spectrometer with an Acousto-Optical Tunable Filter (AOTF). Using in-flight data, we characterized the instrument performance and parameterized its calibration. In particular: an accurate frequency calibration was achieved, together with its variability due to thermal effects on the grating. The AOTF properties and transfer function were also quantified, and we developed and tested a realistic method to compute the spectral continuum transmitted through the coupled grating and AOTF system. The calibration results enabled unprecedented insights into the important problem of the sensitivity of NOMAD to methane abundances in the atmosphere. We also deeply characterized its performance under realistic conditions of varying aerosol abundances, diverse albedos and changing illumination conditions as foreseen over the nominal mission. The results show that, in low aerosol conditions, NOMAD single spectrum, 1σ sensitivity to CH 4 is around 0.33 ppbv at 20 km of altitude when performing solar occultations, and better than 1 ppbv below 30 km. In dusty conditions, we show that the sensitivity drops to 0 below 10 km. In Nadir geometry, results demonstrate that NOMAD will be able to produce seasonal maps of CH 4 with a sensitivity around 5 ppbv over most of planet's surface with spatial integration over 5 × 5° bins. Results show also that such numbers can be improved by a factor of ~10 to ~30 by data binning. Overall, our results quantify NOMAD's capability to address the variable aspects of Martian climate. © 2018 Elsevier Inc. [less ▲]

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See detailUtilisation of Acktar Black coatings in space applications
Plesseria, Jean-Yves ULiege; Marquet, Benoit ULiege; Mazy, Emmanuel ULiege et al

in International Sumposion on Materials in the Space Envrionment (ISMSE) 2018 (2018, September)

Black coatings proposed by the company Acktar present very high light absorbance in a broad wavelength range (13 nm to 14 µm). Various types exist presenting their own advantages and characteristics. For ... [more ▼]

Black coatings proposed by the company Acktar present very high light absorbance in a broad wavelength range (13 nm to 14 µm). Various types exist presenting their own advantages and characteristics. For 2 separate projects, CSL implemented the Fractal Black™ coating from Acktar on flight hardware in order to reach the expected straylight suppression performances. The first project is the S1 mission of the European Space Agency named CHEOPS. This instrument is observing exoplanets via the transit method in order to determine with high accuracy their characteristics. The small telescope is protected from straylight by a baffle, whose design and manufacturing are under responsibility of CSL. In order to reach the high suppression requirement, the Fractal Black™ coating by Acktar was selected as blackening solution for some of the internal surfaces. The size and the presence of a sharp edge challenged the provider but excellent results were achieved. In the frame of this project, samples have been coated and several optical measurements have been performed. Rapid thermal cycling and adhesion tests have also been performed on edge samples in order to confirm the coating adhesion in thermal environment. All these results will be presented in the paper. This baffle has passed all qualification steps at subsystem level and instrument level. CHEOPS will be ready for launch end 2018. The second instrument is the embedded calibration assembly of the UVN instrument of Sentinel-4. Sentinel-4 is part of the Copernicus programme of the European Space Agency that will observe from space the atmosphere pollutants. The calibration assembly, which is under responsibility of CSL, will provide calibration references of the instrument at regular intervals. The reference is obtained from sun-light scattered by a stack of diffusers and illuminating the instrument. The calibration system is preceded by a baffle that should attenuate the stray-light from external sources and mainly Earth limb that will be close to the field of view. On the other hand, it shall avoid any impact of the baffle to the absolute transmission of the diffusers and so it shall reject the light from the Sun which will inevitably scatter inside the baffle. Straylight analyses performed at CSL showed that if a large part of the baffle can use classical black coatings, the last conical sections as well as the diffusers holders need to be darker. Different coatings were considered but Fractal Black™ was again a better candidate for this purpose and this solution was selected. The coating was applied by Acktar on these parts. A first qualification model was submitted, among others, to a straylight test which confirms the rejection performance of the overall assembly. The full qualification campaign has also been run successfully on the calibration assembly and acceptance test are completed on 2 flight models. The results of the straylight analyses and of the straylight tests on various models will be presented in the paper. [less ▲]

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See detailDevelopment of VUV multilayer coatings for SMILE-UVI instrument: theoretical study
Loicq, Jerôme ULiege; baron, Damien; Fleury-Frenette, Karl ULiege et al

in SPIE Conference Proceedings (2018, June)

The Ultraviolet Imager (UVI) instrument is a very challenging imager developed in the frame of the SMILE-ESA mission. The UV camera will consist of a single imaging system targeted at a portion of the ... [more ▼]

The Ultraviolet Imager (UVI) instrument is a very challenging imager developed in the frame of the SMILE-ESA mission. The UV camera will consist of a single imaging system targeted at a portion of the Lyman-Birge-Hopfield (LBH) N2 wavelength band. The baseline design of the imager meets the requirements to record snapshots of auroral dynamics with sufficient spatial resolution to measure cusp processes (100 km) under fully sunlit conditions from the specified apogee of the spacecraft. To achieve this goal, the UVI instrument utilizes a combination of four on-axis mirrors with an intensified FUV CMOS based camera. The mirrors will be coated with spectral selective interferometric layers to provide most of the signal filtering. The objective of these filters is to select the scientific waveband between 160 and 180 nm. The combined four mirrors have to give an out-of-band rejection ratio as high as possible to reject light from solar diffusion, dayglow and unwanted atomic lines in a range of 10-8 – 10-9. Different multilayer coatings are considered and optimized according to the π-multilayer equation for different H/L ratio and for different angles of incidence. Our theoretical evaluation shows a modification of the reflectance spectrum as a function of the angle of incidence, so that the optical beams hitting the different mirrors can have different optical properties depending on the optical fields and the distribution of the rays on the pupil. We will evaluate the effect of fields on the spectral throughput of the UVI instrument based on its optical design. This analysis will be done using the Code V ray-trace software and proprietary scripts. [less ▲]

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See detailOptical alignment of the Solar Orbiter EUI flight instrument
Mazzoli, Alexandra ULiege; Halain, Jean-Philippe; Auchère, Frédéric et al

in ICSO 2018 - International Conference on Space Optics (2018)

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See detailOptical design and optical properties of a VUV spectrographic imager for ICON mission
Loicq, Jerôme ULiege; Kintziger, Christian ULiege; Mazzoli, Alexandra ULiege et al

in Proceedings of SPIE: The International Society for Optical Engineering (2016, June)

In the frame of the ICON (Ionospheric Connection Explorer) mission of NASA led by UC Berkeley, CSL and SSL Berkeley have designed in cooperation a new Far UV spectro-imager. The instrument is based on a ... [more ▼]

In the frame of the ICON (Ionospheric Connection Explorer) mission of NASA led by UC Berkeley, CSL and SSL Berkeley have designed in cooperation a new Far UV spectro-imager. The instrument is based on a Czerny-Turner spectrograph coupled with two back imagers. The whole field of view covers [± 12° vertical, ± 9° horizontal]. The instrument is surmounted by a rotating mirror to adjust the horizontal field of view pointing by ± 30°. To meet the scientific imaging and spectral requirements the instrument has been optimized. The optimization philosophy and related analysis are presented in the present paper. PSF, distortion map and spectral properties are described. A tolerance study and alignment cases were performed to prove the instrument can be built and aligned. Finally straylight and out of band properties are discussed. [less ▲]

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See detailDesign and modelisation of ASPIICS optics
Galy, Camille ULiege; Fineschi, S.; Galano, D. et al

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

In the framework of development of ASPIICS (Association of Spacecraft for Polarimetric and Imaging Investigation of the Corona of the Sun), the Centre Spatial de Liege is responsible of the optical design ... [more ▼]

In the framework of development of ASPIICS (Association of Spacecraft for Polarimetric and Imaging Investigation of the Corona of the Sun), the Centre Spatial de Liege is responsible of the optical design of the coronagraph and the optics will be manufactured by TOPTEC. The particularity of this coronagraph is to have an external occulter located 150 m ahead of the first imaging lens. This external occulter is re-imaged on an internal occulter which function is - as in a classical externally occulted Lyot coronagraph - to block the sun light diffracted by the external occulter and to reduce the straylight on the detector. The selection of this configuration is driven by the requirement to observe the corona as close as possible to the solar limb (i.e. 1 RSun) without imaging the limb itself. A requirement of 1.08 RSun is specified at optical design level to grant 1.2 Rsun at instrument level. The coronograph instrument is designed to have a field of view of 1.6° x 1.6° with a resolution of less than 6 arcsec. Its performances are limited by diffraction in a 530 – 590 nm wavelength range. This paper presents the optical design and demonstrates that by design the requirements are fulfilled within the misalignment, manufacturing and thermo-elastic error contributions. [less ▲]

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See detailThermal Balance Test of Solar Orbiter EUI Instrument Structural and Thermal Model with 13 Solar Constants
Jacques, Lionel ULiege; Halain, Jean-Philippe ULiege; Rossi, Laurence ULiege 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 ultraviolet imager of solar orbiter: optical design and alignment scheme
Halain, Jean-Philippe ULiege; Mazzoli, Alexandra ULiege; Meining, S. et al

in SPIE Optical Engineering+ Applications (2015)

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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 ULiege; zhukova, Maria; Jacques, Lionel ULiege et al

in Proceedings of SPIE: The International Society for Optical Engineering (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 ULiege; 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 ULiege; Rochus, Pierre ULiege; Renotte, Etienne ULiege et al

in Proceedings of SPIE: The International Society for Optical Engineering (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 detailStudy of a solar concentrator for space based on a diffractive/refractive optical combination
Michel, Céline ULiege; Loicq, Jerôme ULiege; Mazzoli, Alexandra ULiege et al

Poster (2013, April 16)

This paper presents a new design of a planar solar concentrator for space applications focusing on two spatially separated PV cells, allowing independent control of output power of each cell. It has the ... [more ▼]

This paper presents a new design of a planar solar concentrator for space applications focusing on two spatially separated PV cells, allowing independent control of output power of each cell. It has the advantages of both spectral splitting and solar concentration by the combination of a blaze transmission diffraction grating and a flat cylindrical Fresnel lens. An optical optimization has been realized and two variations of configuration have been developed to improve tracking tolerance: first, a design completed by secondary reflective concentrators and second, a symmetrical configuration composed of two lenses. First numerical results are presented, highlighting the possibility to design a concentrator at about 10×, with an electrical output power about 290W/m² lens and less than 10% losses for tracking errors lower than ±0.9°. [less ▲]

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See detailThe SWAP EUV Imaging Telescope. Part II: In-flight Performance and Calibration
Halain, Jean-Philippe ULiege; 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 detailStudy of a solar concentrator for space based on a diffractive/refractive optical combination
Michel, Céline ULiege; Loicq, Jerôme ULiege; Languy, Fabian ULiege et al

in AIP Conference Proceedings (2013), (1556), 97-100

This paper presents a new design of a planar solar concentrator for space applications focusing on two spatially separated PV cells, allowing independent control of output power of each cell. It has the ... [more ▼]

This paper presents a new design of a planar solar concentrator for space applications focusing on two spatially separated PV cells, allowing independent control of output power of each cell. It has the advantages of both spectral splitting and solar concentration by the combination of a blaze transmission diffraction grating and a flat cylindrical Fresnel lens. An optical optimization has been realized and two variations of configuration have been developed to improve tracking tolerance: first, a design completed by secondary reflective concentrators and second, a symmetrical configuration composed of two lenses. First numerical results are presented, highlighting the possibility to design a concentrator at about 10×, with an electrical output power about 290W/m² lens and less than 10% losses for tracking errors lower than ±0.9°. [less ▲]

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See detailStudy of a solar concentrator for space based on a diffractive/refractive optical combination
Michel, Céline ULiege; Loicq, Jerôme ULiege; Languy, Fabian ULiege et al

Conference (2012, November 12)

This paper presents a new design of a planar solar concentrator at 10× with spectral splitting focusing on two separated PV cells, allowing independent control. Optical elements, blazed diffraction ... [more ▼]

This paper presents a new design of a planar solar concentrator at 10× with spectral splitting focusing on two separated PV cells, allowing independent control. Optical elements, blazed diffraction grating and Fresnel lens, are optimized. [less ▲]

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See detailEUV high resolution imager on-board Solar Orbiter: optical design and detector performances.
Halain, Jean-Philippe ULiege; Mazzoli, Alexandra ULiege; Rochus, Pierre ULiege 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 detailA Target Projector for Videogrammetry under Vacuum Conditions
Roose, Stéphane ULiege; Mazzoli, Alexandra ULiege; Barzin, Pascal ULiege et al

Scientific conference (2012, March 21)

Videogrammetry is a 3-dimensional co-ordinate measuring technique that (now) uses digital image capture as the recording method. Images are taken from at least two different locations and the light-rays ... [more ▼]

Videogrammetry is a 3-dimensional co-ordinate measuring technique that (now) uses digital image capture as the recording method. Images are taken from at least two different locations and the light-rays from the camera to the measurement object are intersected by triangulation into 3D point coordinates. With a large number of images, the camera orientation and 3D point locations are accurately determined with the use of a full mathematical model (bundle adjustment). Adhesive targets are commonly used for point materialization. Those targets consist of a retro-reflective material, with an adhesive backing for sticking to the structure under investigation. A drawback of these types of targets is that they can lose their adhesion and shape during thermal vacuum cycling, especially when cryogenic temperatures are involved. In addition the operation of placing and removing targets is a critical procedure that can lead to undesirable contamination and damage to the test item. Because they require to be physically attached to the surface to be measured, this can also compromise the quality assurance of the test object. Such problems were encountered during cryogenic thermal vacuum qualification testing of the ESA Planck Surveyor mission telescope reflectors. In the development described here the aim was to replace the use of adhesive targets by projected dots. The idea is not fundamentally new. Indeed a US company, Geodetic Systems Inc. (GSI) proposes already a commercial target projector for videogrammetry which uses a flashlamp and is adequate for workshop and laboratory applications. Dot projection videogrammetry is also suggested as a shape measurement method of Gossamer structures, membrane reflectors, etc…Note that there are fundamental differences in use and applications of retro-reflective targets and dot projection: • Retro-reflective targets are materialized on the test article. They appear as fiducials attached to the test article. Any relative distortion of the materialized point can be tracked with respect to the test article itself. • Projected dots are not materialized on the object. Practically a specific point cannot be tracked by this method. The dense cloud of projected dots allows sampling the surface or the shape in an arbitrary way.The Target Projector System (TPS), described here (Fig.1), was designed and manufactured to operate in the Large Space Simulator (LSS) of ESAof ESA under thermal vacuum conditions and to have a minimized temperature exchange with its environment. It is operational over a temperature range of 90K to 350 K, and has a wavelength of 808 nm.Qualification tests and results under vacuum, along with an assessment of the videogrammetric accuracy achievable for various configurations of this unique device are presented. [less ▲]

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See detailJupiter system Ultraviolet Dynamics Explorer (JUDE), an instrument proposed for the ESA-JUICE mission
Grodent, Denis ULiege; Bunce, Emma J.; Renotte, Etienne ULiege et al

Report (2012)

In the proposal that follows we present a detailed concept for the science case, instrument requirements, technical design, calibration and operations, management structure, and financial plan for the ... [more ▼]

In the proposal that follows we present a detailed concept for the science case, instrument requirements, technical design, calibration and operations, management structure, and financial plan for the Jupiter system Ultraviolet Dynamics Experiment (JUDE), which will provide an outstanding solution to the UV instrumentation requirements for the JUICE mission. The JUDE instrument will represent a novel technical capability in UV instrumentation for planetary science, and will deliver the first true UV imaging capability beyond Earth orbit. The JUDE instrument design consists of two separate channels – the imaging channel (ImaC) and the spectrograph channel (SpeC), neither of which has any moving parts. This simple combination of two autonomous channels allows a true image and a spectrum at FUV wavelengths to be obtained simultaneously, allowing science goals to be realised which are not possible with a traditional scanning-slit imaging-spectrograph design The international consortium assembled to build the JUDE instrument is formed of two institutes from two European countries, and one from the United States. Prof. Denis Grodent (Université de Liège, Belgium) will act as the PI for the entire instrument team and the ULg/CSL team will provide a substantial hardware contribution to the instrument in the form of the optics, coatings, and Data Processing Unit (DPU). Dr Emma Bunce (University of Leicester, UK) will act as Co-PI for the instrument and the UoL team will supply the Micro-Channel Plate (MCP) detectors and read-out electronics. Prof. John Clarke (Co-I) of Boston University, USA will provide the grating element for the spectral channel of the instrument, in addition to instrument calibration activities. The science Co-Is are gathered from multiple institutes/nations including Belgium, UK, Germany, Italy, and the United States (see Part 1 for the full team list). Collectively, the team have decades of expertise in the areas of outer planet magnetospheres, planetary auroral and atmospheric emissions and surface UV observations from multiple platforms including Cassini UVIS, Juno UVS, Hubble Space Telescope, and numerous terrestrial missions. The team also have roles on non-UV instruments which will maximise the interpretation of the JUDE data. The two instrument channels are built on proven and robust technology with much flight heritage (e.g. Juno, Cassini, BepiColombo, IMAGE, ROSAT, Chandra, Voyager, Freja, DE-1, Swift). More specifically, the optics and focal plane detector proposed for the JUDE instrument are widely based on previous designs by CSL, at the ULg and UoL, for the FUV Spectro-Imager on the NASA IMAGE spacecraft, the UV Spectrograph on the NASA Juno mission to Jupiter, and the ROSAT Wide Field Camera. The data return from the instrument will greatly benefit the European and international science communities in planetary and terrestrial sciences, and the knowledge obtained will be generally applicable to broader astrophysics disciplines (e.g. extrasolar planetary physics). In answering the UV science objectives for the JUICE mission the JUDE instrument will clearly address the ESA Cosmic Vision Themes 1: What are the conditions for planet formation and the emergence of life? and 2: How does the Solar System work? The JUDE images (in particular) provide a clear path towards a high-level related programme of education and public outreach which the JUDE team are well equipped and keen to exploit. The JUDE instrument will contribute to all of the UV-related science objectives of JUICE, plus additional science objectives not listed in the Science Requirements Matrix. - At Ganymede and other moons (Europa and Callisto) JUDE will contribute directly to breakthroughs in the following scientific areas: 1) the characterisation of local environment, specifically through the first investigation of the morphology and variation of Ganymede’s aurora. A clear understanding of the auroral and atmospheric emissions at Ganymede will provide vital information on their formation mechanisms and will contribute to studies of the interaction of the Ganymede magnetosphere with Jupiter’s magnetosphere; 2) the first detailed observations of the satellites’ atmospheric (exosphere/ionosphere) composition and structure through measurements of their atmospheric emission and absorption spectra during multiple stellar occultation opportunities; and 3) the study of the satellites surface composition using surface reflectance measurements. The measurements at UV wavelengths are essential because they allow the study of the relationship between the satellites’ surface weathering, their atmospheres and the external environment which is mainly affected by the surrounding Jovian magnetosphere. By carefully studying processes at the surface and in the satellites’ atmospheres together, JUDE will provide the information required to distinguish between two classes of compositional heterogeneities at the satellites’ surfaces: 1) heterogeneities that arise from interaction with the external environment; 2) heterogeneities that arise from dynamical interaction with the subsurface. - With respect to Jupiter, JUDE will: 1) provide “state of the art” measurements of the Jovian atmospheric dynamics and transport through high temporal and spatial resolution auroral imaging; 2) allow a new understanding of the Jovian magnetosphere as a fast rotator through interpretation of the Jovian aurora as direct evidence for the 3D magnetosphere dynamics – a view which is continuously available in the planet’s upper atmosphere (independent of the spacecraft location within the magnetosphere); 3) investigate the magnetosphere as a giant accelerator through observations of the field-aligned current systems responsible for acceleration of electrons (and production of aurora); 4) discover the plasma sources and sinks of the moons through auroral imaging of the moon footprints in Jupiter’s atmosphere as a witness of the electromagnetic interactions taking place; 5) obtain new information on Jupiter’s atmospheric structure and composition through multiple stellar occultation opportunities. In addition, JUDE will make remote observations of the Io torus emissions and will provide the first in situ observation of the variability of the torus, over the lifetime of the mission, providing important information about the internal activity of the moon. JUDE offers a unique opportunity to obtain the first concurrent datasets of the different coupled elements of the Jupiter system: Io's atmosphere, aurora, the plasma torus, the Jovian plasma sheet and the Jovian aurora. The JUDE imaging and spectral channels are both designed to capture FUV lines from sulphur ions in the Io plasma torus. Finally, JUDE’s remote sensing capability offers an exciting opportunity to discover the Europa “plume” activity that may be present, through limb observations during flybys and from more distant observing locations. The Ganymede-focused and moon related science objectives will be addressed in the Ganymede orbit phase and during the multiple moon flybys, whilst the Jupiter science will be predominantly achieved during the Jupiter Equatorial Phases and during the high-inclination phase. The JUDE UV imager and spectrograph will produce discovery level science at Ganymede and the first true 2D UV images from Jupiter orbit. The exceptional JUICE trajectory affords many opportunities for breakthrough science discoveries in accordance with the SciRD; in addition to those, it provides unprecedented opportunities to directly witness the electromagnetic connection between Ganymede and Jupiter by making the first simultaneous UV observations of the respective atmospheres within the JUDE field-of-view. This is possible as a direct consequence of the JUDE true imaging capability. To successfully meet the science requirements outlined above, the JUDE ImaC has a spatial resolution of 20 arcsec over a circular field-of-view with 6˚ diameter, which allows a 100 km spatial resolution on Jupiter from Ganymede orbital distances (and 20 m resolution on Ganymede from 200 km, for example). JUDE’s ImaC mirrors and detector window will be covered with multilayer coatings which efficiently select a narrow bandpass from 130 to 143 nm, to allow measurements of the faint Oxygen lines at 130.4 nm and 135.6 nm in Ganymede’s (and other moon’s) atmosphere. This bandpass also allows observations of the SIV lines (between 140.5 and 142.4 nm) emitted within the Io plasma torus and in Io’s atmosphere. The bright Jovian emissions will also be suppressed within this bandpass which will necessarily limit the count rate to an acceptable level. The Ly-α line at 122 nm will be largely excluded as will the reflected sunlight longward of 150 nm. The sensitivity of the ImaC is 50 Rayleigh (at 3-sigma). The SpeC has a spectral resolution of 0.5 nm in order to meet the requirements of the SciRD, and has a field-of-view which is a 6˚ x 0.1˚ slit co-aligned with, and centred on, the ImaC circular field-of-view. The lower wavelength of the SpeC bandpass is set to ~110 nm in order to include the bright Ly-α line (useful to study the H corona) in a region of reduced transmission. The upper wavelength limit, ~195 nm, is such that transmission is slowly decreasing in the 180-195 nm spectral region, allowing measurements of the moon’s albedos beyond 165 nm, as well as the detection of compounds such as CO2, SO2, O2, O3, H2CO3 and H2O2 by comparing JUDE reflectance spectra to those obtained in laboratory studies. FUV emission lines from S and O are also observable within the bandpass and B-type stars emitting within this waveband will allow occultation experiments to be performed, to determine the composition and structure of the moon’s atmospheres and the detection of a possible Europa plume. The same is true for the Jovian atmosphere for which attenuation by H2 and hydrocarbons allows determination of the atmospheric structure. The sensitivity of the SpeC is 10 R/nm (at 3-sigma). The JUDE instrument channels: ImaC and the co-aligned SpeC, are both operating within the 110–195 nm range. Each channel has independent optics and detector elements, providing a level of redundancy such that loss of either imager or spectrograph does not constitute an entire loss of science. In contrast to more conventional (e.g. scanning or pushbroom) imaging spectrographs, JUDE can provide high time resolution (<1 second) high throughput images over a wide field of view (6° diameter) with no time variation across the field – a capability which is critical in gaining a better understanding of the complex dynamical processes taking place in the Jovian magnetosphere. The primary optic in each channel is a multilayer-coated mirror operating at normal incidence, with flight heritage in the form of the scan mirror in the Ultraviolet Spectrograph (UVS) now en-route to Jupiter onboard JUNO. The imaging channel uses a secondary mirror to of a similar type to focus the image onto the focal plane detector, while in the spectrograph channel, the secondary is a spherical, holographic grating. The spectrograph design is simple, with heritage in airglow spectrographs flown on terrestrial UV missions, and the Imaging UV Spectrograph for MAVEN. The grating element is produced by Jobin-Yvon, who have produced diffraction gratings for major missions including SOHO and HST. Each channel includes an identical microchannel plate (MCP) detector with the robust, radiation-tolerant performance required for a mission in the formidable environment of Jupiter. Such detectors are well proven, having flown on many missions including ROSAT (UoL heritage). They have also operated in the vicinity of Jupiter, in the focal plane of the UV spectrograph onboard the Voyager probes. The detector readout is a new type of capacitive division image charge readout (C-DIR; invented by Dr Jon Lapington) which offers, simultaneously, high spatial resolution and high count rate performance. Adaptive signal processing capabilities allow JUDE to accommodate the very wide dynamic range expected, from observations of Jupiter’s auroral ovals which emit with intensities of mega Rayleighs, to the weak (few tens of Rayleigh) emissions found at Ganymede. The readout structure is simple and robust, and has already been demonstrated in laboratory trials, while the electronics chain has its heritage in particle physics detectors, and has therefore been designed with radiation tolerance as a primary consideration. Pre-launch and in-flight calibrations will be implemented to assure that the JUDE data are suitable for quantitative scientific analysis. The proposed JUDE configuration successfully meets the scientific objectives of the JUICE mission. Our decision to implement an imaging channel instead of covering the MUV waveband increases the whole mission’s scientific output while remaining compliant with the MPDD. Due to its high-temporal resolution read-out system, JUDE is capable of producing volumes of data that are incompatible with the limited telemetry allocated to the UV instrument, even after a modest compression factor is applied. We therefore have proposed a mode of operation (the JUDE reference mode) which takes 1 minute snapshots over an observation opportunity (for example during a flyby sequence). Using this reference mode, and taking the maximum count rate estimates for the various targets, we find that the JUDE data volume is compliant with the tight allocation for the UV instrumentation of 40 GBytes/year The JUDE design presented in this proposal is above the mass allocation. We believe that all components of our design are necessary to reach the scientific goals of JUICE mission and that any major changes (such as the descope of a channel) will be at the considerable expense of the expected science return. However, further optimisation will be performed during the Phase A to bring JUDE into the allocated mass envelope while compromising its scientific return only slightly. We propose an efficient management structure with clearly delineated responsibilities. The Principal Investigator, Prof. Denis Grodent (Be) will take on the responsibilities as specified in the JUICE payload Announcement of Opportunity, supported closely by the Co-PI Dr Emma Bunce (UK) and by the team of Co-Investigators. The contribution of each country is represented by lead Co-Investigators: Prof. John Clarke (Boston University), Dr. Candy Hansen (PSI), and Dr Xianzhe Jia (University of Michigan), and Dr Nigel Bannister (UK) as CoI and Instrument Scientist (see Figure 1 below). The philosophy has been to assign well-defined tasks to each institute with an overall project manager to coordinate the efforts. The Consortium Project Manager (Etienne Renotte, CSL) will execute the managerial tasks relevant to the instrument development. The Product and Quality Assurance management will be implemented by all hardware contributors. Each consortium institute has a local project manager for their respective work packages, reporting to the Consortium Project Manager. The outreach potential of JUDE’s instantaneous wide field images is enormous. The potential PhD students of 2030 who we hope to educate and inspire with JUDE images and spectra are currently 3 years old; their supervisors are in secondary school. The team regards the educational aspects of the instrument and data as particularly important, and we plan a comprehensive JUDE/JUICE programme of outreach to schools and to the public, as part of the project and one which will be initiated upon selection. The national funding agency of Belgium serves as the Lead Funding Agency (LFA) for the JUDE instrument. The letters of endorsement from Belgium and United Kingdom are included in this proposal. Although the agencies endorse their respective national contributions, funding will be secured after the selection of the instrument proposal, according to the usual procedure. [less ▲]

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