Publications of Jerôme Loicq
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See detailSolution uniqueness and noise impact in a static spectropolarimeter based on birefringent prisms for full Stokes parameter retrieval
Vasilescu, Bogdan ULiege; Loicq, Jerôme ULiege; Nazé, Yaël ULiege

in Journal of Astronomical Telescopes, Instruments, and Systems (2020), 6(2),

An innovative model of a static spectropolarimeter able to cover the entire Stokes vector is discussed. The optical layout is based on a birefringent modulator formed by two antiparallel prisms stuck ... [more ▼]

An innovative model of a static spectropolarimeter able to cover the entire Stokes vector is discussed. The optical layout is based on a birefringent modulator formed by two antiparallel prisms stuck together with the help of an intermediary part of the same material. This optical model has the advantage of being extremely compact. It avoids any movable parts or rotating components. By its architecture, the device induces a complete modulation on the vertical direction of any incoming polarized light, facilitating the determination of the entire Stokes vector through a single measurement. Because the modulation is also wavelength-dependent, spectral dependencies of the polarization states can be derived. The behavior of the model was first investigated in noise-free conditions. The existence of a unique solution was proven in the absence of noise and for any Stokes vector configuration. Under noisy conditions, the uncertainty on the Stokes parameters and the efficiency of the modulation scheme were evaluated as a function of the analyzer’s angle and for two different configurations of the modulator. The simulations show that an almost ideal efficiency is reachable, qualifying the concept for the high-precision measurement of the polarization. [less ▲]

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See detailOpal-Like Photonic Structuring of Perovskite Solar Cells Using a Genetic Algorithm Approach
Lobet, Michaël ULiege; Mayer, Alexandre; Maho, Anthony ULiege et al

in Applied Sciences (2020)

Light management is an important area of photovoltaic research, but little is known about it in perovskite solar cells. The present work numerically studies the positive effect of structuring the photo ... [more ▼]

Light management is an important area of photovoltaic research, but little is known about it in perovskite solar cells. The present work numerically studies the positive effect of structuring the photo-active layer of perovskite material. This structuration consists of a hybrid absorbing layer made of an uniform part and an opal-like part. A genetic algorithm approach allows us to determine the optimal combination among more than 1.4 􀵈 10􀬽 potential combinations. The optimal combination provides an internal quantum efficiency of 98.1%, nearly 2% higher than for an equivalent unstructured photo-active layer. The robustness of the optimum against potential experimental deviations, as well as the angular dependency of the proposed structure, are examined in the present study. [less ▲]

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See detailTechnological challenges for the Large Interferometer For Exoplanets (LIFE)
Defrere, Denis ULiege; Quanz, Sascha; Absil, Olivier ULiege et al

Scientific conference (2019, November 04)

LIFE is a project initiated in 2017 and officially kicked-off in 2019 to develop the science, technology and a roadmap for an ambitious space mission that will allow mankind for the first time to detect ... [more ▼]

LIFE is a project initiated in 2017 and officially kicked-off in 2019 to develop the science, technology and a roadmap for an ambitious space mission that will allow mankind for the first time to detect and characterize the atmospheres of dozens of warm, terrestrial extrasolar planets. Thanks to NASA's Kepler mission and dedicated, long-term exoplanet searches from the ground, we know that rocky exoplanets are ubiquitous in the Milky Way and very likely also in the immediate Solar neighbourhood. Detecting these nearest planets, understanding the (atmospheric) diversity of other worlds and searching for indications of habitability and biological activity is a cornerstone of 21st century astrophysics and will provide us a new perspective on our place in this Universe. After a brief introduction on the scientific objectives, we present in this talk the recent technology developments required for LIFE and present the main technological challenges to tackle before launching such a mission. [less ▲]

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See detailUsing a cubesat to improve irrigation: an innovative thermal imager
Laborde, Victor ULiege; Loicq, Jerôme ULiege; Habraken, Serge ULiege et al

Conference (2019, September 11)

Water management has become one of the most important issues since 70% of the fresh water available on Earth is used for irrigation. The growing food demand and the scarcity of water resources lead to the ... [more ▼]

Water management has become one of the most important issues since 70% of the fresh water available on Earth is used for irrigation. The growing food demand and the scarcity of water resources lead to the need to carefully monitor water use, considering agricultural fields of thousands of km². The intrinsic hydric stress of crops is an indicator of their water needs. Better water management and crops healthiness could be achieved if this stress could be measured quickly. Hydric stress can be retrieve by comparing the ground temperature (reference) and the leaf surface temperature (LST) which also depends on the transpiration ability of the plant. Yet, this measure is very unpractical without airborne/spaceborn sensors with good resolution. This finding has led to the birth of the OUFTI-NEXT mission. The recent advances in the field of nanosatellites and the rising attention they get from the space agencies have convinced the University of Liege to develop its own CubeSat mission to image the LST with thermal infrared light above extensive crops to provide data for irrigation schedule. The aim of the long term mission will be to fly a constellation of CubeSats to ensure daily coverage over various fields with resolution of 50m. In addition, hot singular events data can be retrieved such as forest fire, volcanoes activity, pollutant leaking, etc… Each CubeSat is a dual-band imager in both the middle wave infrared (MWIR) and the long wave infrared (LWIR). The scientific value of combining these bands is huge since LWIR gives accurate temperature measurements around 300K but with bad contrast, the latter being compensated by the MWIR which allows fine resolution. Each band is also sensitive to different atmosphere condition (humidity, clouds) and using both brings robustness to the mission. The current step of this ambitious project is to fly a single band 3U technology demonstrator to validate the use of MWIR technologies without space heritage and the scientific value of MWIR images for LST determination. This spectral band is very challenging, as it hardly allows diffraction-limited performances: it requires fast optics, more sensitive to aberrations. For this demonstrator, resolution of 100m without daily coverage is chosen, resulting from is a trade-off between science demonstration and mission size. The “new” infrared technologies include: high operating temperature detector, compact optics, passive athermalization and recent infrared materials. Solutions to make this challenging mission feasible are promising: The MWIR camera achieved diffraction-limited performances and uses compact hybrid lenses made of chalcogenide materials to reduce thermals effects and manufacturing costs. A very wide range of suitable detectors have been reviewed and the possibility to customize their integration is studied with their manufacturers. The orbit is sun-synchronous to optimize the thermal design and in accordance with both the radiometric budget and the observation strategy. [less ▲]

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See detailFeasibility study of an interferometric CubeSat for exoplanet science
Dandumont, Colin ULiege; Loicq, Jerôme ULiege; Defrere, Denis ULiege et al

Conference (2019, September 11)

Every week, new exoplanets are discovered mostly by the transit method (77.1% of all discoveries according to NASA). Even if this method is efficient at detecting planets, it is limited to a small ... [more ▼]

Every week, new exoplanets are discovered mostly by the transit method (77.1% of all discoveries according to NASA). Even if this method is efficient at detecting planets, it is limited to a small fraction of the whole expected exoplanets population due to the low probability of planetary transit. Therefore, a direct method is needed to detect and characterize exoplanets around the nearest stars. In this case, the planet and the star are angularly separated and photons are distinguished. It leads to the detection of the planet. Moreover, it allows the possible characterization of the planet surface or its atmosphere. One way to detect them through direct method is to use interferometry. With at least two sub-pupils (Bracewell interferometer), coherent light from the target is recombined to form interference patterns. The angular resolution depends on the baseline (distance between the two sub-pupils) and not on the diameter of each sub-pupil. Instead of using a single large telescope (around 60 cm diameter), which does not fit into a CubeSat, one can use two small and well separated apertures (around 10 cm each) to synthesize this large telescope. Therefore, it increases drastically the resolution power of CubeSats. In order to detect an exoplanet and get the direct light coming from it, the light from the star must be mitigated. It is called nulling interferometry. Thanks to a pi phase shift induced in one arm of the interferometer, destructive interferences are produced on the line-of-sight in order to suppress the light of the star. The exoplanet, which is on constructive interferences (white fringes), is unveiled. The Centre Spatial de Liège of the University is developing a space-based interferometer with a CubeSat. Goals are twofold: observe the nearest stars and demonstrate this technology in space, which will be a premiere. It is the first step towards a future large interferometry space-based mission which has the ambition to spectrally characterize Earth-like planets. The CubeSat will demonstrate light injection to optical fibers, recombination of the two beams, control of the delay-lines and detection. CubeSats offer low-cost demonstrator capabilities with a fixed baseline and with no free-flying concept. Aside the technical challenges, the second part of our researches is focused on the detection possibilities with this type of nanosatellite. We estimate by numerical simulations the possible science return for such an instrument. [less ▲]

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See detailAtmospheric characterization of terrestrial exoplanets in the mid-infared: biosignatures, habitability & diversity
Quanz, Sascha P.; Absil, Olivier ULiege; Angerhausen, Daniel et al

E-print/Working paper (2019)

Exoplanet science is one of the most thriving fields of modern astrophysics. A major goal is the atmospheric characterization of dozens of small, terrestrial exoplanets in order to search for signatures ... [more ▼]

Exoplanet science is one of the most thriving fields of modern astrophysics. A major goal is the atmospheric characterization of dozens of small, terrestrial exoplanets in order to search for signatures in their atmospheres that indicate biological activity, assess their ability to provide conditions for life as we know it, and investigate their expected atmospheric diversity. None of the currently adopted projects or missions, from ground or in space, can address these goals. In this White Paper we argue that a large space-based mission designed to detect and investigate thermal emission spectra of terrestrial exoplanets in the MIR wavelength range provides unique scientific potential to address these goals and surpasses the capabilities of other approaches. While NASA might be focusing on large missions that aim to detect terrestrial planets in reflected light, ESA has the opportunity to take leadership and spearhead the development of a large MIR exoplanet mission within the scope of the "Voyage 2050'' long-term plan establishing Europe at the forefront of exoplanet science for decades to come. Given the ambitious science goals of such a mission, additional international partners might be interested in participating and contributing to a roadmap that, in the long run, leads to a successful implementation. A new, dedicated development program funded by ESA to help reduce development and implementation cost and further push some of the required key technologies would be a first important step in this direction. Ultimately, a large MIR exoplanet imaging mission will be needed to help answer one of mankind's most fundamental questions: "How unique is our Earth?'' [less ▲]

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See detailDevelopment of a space-based nulling interferometer to detect and characterize exoplanets
Schifano, Luca; Defrere, Denis ULiege; Absil, Olivier ULiege et al

in Proceedings of SPIE: The International Society for Optical Engineering (2019, July 12)

The development of small space-based platforms for nulling interferometric observations could be the pathfinder of a new era in exoplanetology. While planetary transit and radial velocity are the most ... [more ▼]

The development of small space-based platforms for nulling interferometric observations could be the pathfinder of a new era in exoplanetology. While planetary transit and radial velocity are the most productive ways to detect exoplanets, such techniques are indirect detections. For deeper characterization of exoplanets, direct detection techniques should be developed. By injecting direct light coming from exoplanets into spectrometers, we could study their chemical composition, search for biosignatures, and possibly infer the presence of life. The low number of photons to be gathered from the planets, high contrast with the star and small angular resolution are the major difficulties for a direct detection. However, nulling interferometry seems to be a solution to tackle these challenges. By combining the light of two or more telescopes, we would considerably increase the angular resolution, and thus could potentially lead to the detection of Earth-size rocky exoplanets around Solar-type stars. Moreover, with a π- phase shift between the two interferometer arms, the starlight is reduced which allows the detection of much fainter objects around the star. In this paper it will be presented the development of a new mission based on nulling interferometry and dedicated to the Alpha Centauri system. As our nearest stellar system, it is a prime target to investigate for the research of new worlds. Monte-Carlo simulations about potential exoplanet yield of such an interferometer will be described, for different assumptions such as the detection wavelength and telescope size. Single-mode fibers and integrated optics will also be investigated for this mission. This could lead to low-cost type missions with a high potential of scientific return. [less ▲]

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See detailTopography and Longitudinal Chromatic Aberration characterizations of Refractive-Diffractive Multifocal IOLs
Loicq, Jerôme ULiege; Willet, Nicolas ULiege; Gatinel, Damien

in Journal of Cataract and Refractive Surgery (2019)

Purpose Most optical systems present chromatic aberration quantified along the optical axis by the longitudinal chromatic aberration (LCA). LCA is controlled by the biomaterial Abbe number combined with ... [more ▼]

Purpose Most optical systems present chromatic aberration quantified along the optical axis by the longitudinal chromatic aberration (LCA). LCA is controlled by the biomaterial Abbe number combined with diffractive effects, driven by the IOL topography. This paper experimentally aims at describing in vitro the effect of LCA in diffractive multifocal IOLs, with the help of dedicated optical benches and topographic characterization. Setting Centre Spatial de Liege. Design Optical and topology analysis of various Multifocal diffractive intraocular lenses. Methods Seven diffractive multifocal lenses, available on the market and exhibiting different diffractive profiles, made from various biomaterials, were characterized under different wavelengths. Results Through-focus Modulation Transfer Function (MTF) curves and IOL diffraction efficiency depends on the incident light wavelength. In this paper, we investigated the topology properties of various Multifocal intraocular lenses and correlated their characteristics to their optical behavior for various wavelengths. Chromatic properties and their origins were then compared. As expected, diffractive and refractive effects were found to act in opposite ways, and could be partially or completely compensated. Conclusions The longitudinal chromatic aberration of each of the lenses was evaluated in vitro. In most of the MIOLs studied, some of the foci were found to be refractive, while others were diffractive. Although the results were not extrapolated to clinical relevance , it was shown, in some of the cases, that LCA could be fully compensated. [less ▲]

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See detailOpal-like CH3NH3PbI3 perovskite solar cells : effect of the 3D structuration on the conversion efficiency
Dewalque, Jennifer ULiege; Daem, Nathan ULiege; Spronck, Gilles ULiege et al

Poster (2019, May 13)

In this work, the 3D structuration of perovskite films is studied in order to highlight the effect of a periodic porous structure on the optical properties of the films (light harvesting, optical ... [more ▼]

In this work, the 3D structuration of perovskite films is studied in order to highlight the effect of a periodic porous structure on the optical properties of the films (light harvesting, optical coloration, semi-transparency…) and on the PV efficiency, in comparison with dense perovskite films usually used in planar solar cells configuration. The opal-like perovskite scaffold is obtained from templating fabrication method, with polystyrene beads as structuring agent. Five PS bead diameters are studied: 300 nm, 540 nm, 810 nm, 1.0 µm and 2.1 µm, to highlight the effect of the PS bead diameter on the optical properties of the films and on the PV efficiency. PbI2/CH3NH3I 0.7M in DMSO leads to the most covering, homogeneous and overlayer-free porous films. The PV efficiency of the corresponding cells increases with the bead diameter. A significant improvement in the PV conversion efficiency is observed thanks to the 3D structuration compared to a dense reference, due to the improvement of charge separation at the Spiro-OMeTAD/perovskite interface and thus to the reduction of charge recombination. In addition, CH3NH3PbI3 porous films prepared with 810 nm, 1000 nm and 2100 nm PS bead diameter respectively, are coloured, which is very interesting for building-integrated applications (BIPV). [less ▲]

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See detailCharacterizing the atmosphere of Proxima b with a space-based mid-infrared nulling interferometer
Defrere, Denis ULiege; Léger, A.; Absil, Olivier ULiege et al

in Proceedings of SPIE: The International Society for Optical Engineering (2018, July 09), 10701

Proxima b is our nearest potentially rocky exoplanet and represents a formidable opportunity for exoplanet science and possibly astrobiology. With an angular separation of only 35 mas (or 0.05 AU) from ... [more ▼]

Proxima b is our nearest potentially rocky exoplanet and represents a formidable opportunity for exoplanet science and possibly astrobiology. With an angular separation of only 35 mas (or 0.05 AU) from its host star, Proxima b is however hardly observable with current imaging telescopes and future space-based coronagraphs. One way to separate the photons of the planet from those of its host star is to use an interferometer that can easily resolve such spatial scales. In addition, its proximity to Earth and its favorable contrast ratio compared with its host M dwarf (approximately 10-5 at 10 microns) makes it an ideal target for a space-based nulling interferometer with relatively small apertures. In this paper, we present the motivation for observing this planet in the mid-infrared (5-20 microns) and the corresponding technological challenges. Then, we describe the concept of a space-based infrared interferometer with relatively small (<1m in diameter) apertures that can measure key details of Proxima b, such as its size, temperature, climate structure, as well as the presence of important atmospheric molecules such as H2O, CO2, O3, and CH4. Finally, we illustrate the concept by showing realistic observations using synthetic spectra of Proxima b computed with coupled climate chemistry models. © 2018 SPIE. [less ▲]

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See detailNƎSIE: a fiber-fed near-infrared spectrograph for TIGRE telescope
Kintziger, Christian ULiege; Rauw, Grégor ULiege; Desselle, Richard ULiege et al

in Evans, Christopher; Simard, Luc; Takami, Hideki (Eds.) Proceedings Volume 10702, Ground-based and Airborne Instrumentation for Astronomy VII (2018, July 06)

Our contribution intends to present the obtained performances of the NƎSIE instrument, a new near-infrared fiber-fed spectrograph developed at the University of Liège. This instrument was developed ... [more ▼]

Our contribution intends to present the obtained performances of the NƎSIE instrument, a new near-infrared fiber-fed spectrograph developed at the University of Liège. This instrument was developed, aligned and tested at the Centre Spatial de Liège and first light was achieved in October 2017. This paper will go through the alignment process and optical performance verification to eventually introduce the first light observations. The final location of NƎSIE will be the TIGRE telescope located in La Luz, Mexico. The observational data provided by this instrument will help several research groups from the University of Liège to study massive stars. In particularly, evolution models will be improved through the comparison of the collected spectra with theoretical models. This collaboration will therefore contribute to a better understanding of massive stars and the mechanisms that take place within these extraordinary objects. [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 detailLight-harvesting capabilities of dielectric sphere multilayers
Baron, Damien ULiege; Dewalque, Jennifer ULiege; Henrist, Catherine ULiege et al

in Proceedings of SPIE: The International Society for Optical Engineering (2018, March), 10541

Self-assembled synthetic opals are suitable for integration into solution-processed thin film solar cells. In this work, finite-difference time-domain simulations are carried out to tailor optical ... [more ▼]

Self-assembled synthetic opals are suitable for integration into solution-processed thin film solar cells. In this work, finite-difference time-domain simulations are carried out to tailor optical properties of monolayer and multilayers of semiconductor spheres to trap light when these structures are incorporated into thin film solar cells. In particular, architectures in which spheres are filled with a photoactive material and embedded in a lower refractive index medium are examined. Based on spectra and field intensity maps, this study demonstrates that opal-like photonic crystals obtained from colloidal templates and filled with light-absorbing material can significantly harvest light by exploiting photonic band resonances. [less ▲]

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See detailOUFTI-Next: the second cubesat of the university of Liège
Werner, Xavier ULiege; Habraken, Serge ULiege; Kerschen, Gaëtan ULiege et al

in Advances in the Astronautical Sciences (2018)

the ULiège selected the concept of an earth observation 3U CubeSat and corresponding ground segment to produce images in the mid-wave infrared (MWIR), dedicated to measure the hydric stress of vegetation ... [more ▼]

the ULiège selected the concept of an earth observation 3U CubeSat and corresponding ground segment to produce images in the mid-wave infrared (MWIR), dedicated to measure the hydric stress of vegetation. This monitoring would allow farmers to provide optimal irrigation to their crops and thus will lead to spare drinkable water. [less ▲]

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See detailThe Far Ultra-Violet Imager on the Icon Mission
Mende, Stephen; Frey, Harald; Rider, Kodi et al

in Space Science Reviews (2017)

ICON Far UltraViolet (FUV) imager contributes to the ICON science objectives by providing remote sensing measurements of the daytime and nighttime atmosphere/ ionosphere. During sunlit atmospheric ... [more ▼]

ICON Far UltraViolet (FUV) imager contributes to the ICON science objectives by providing remote sensing measurements of the daytime and nighttime atmosphere/ ionosphere. During sunlit atmospheric conditions, ICON FUV images the limb altitude profile in the shortwave (SW) band at 135.6 nm and the longwave (LW) band at 157 nm perpendicular to the satellite motion to retrieve the atmospheric O/N2 ratio. In conditions of atmospheric darkness, ICON FUV measures the 135.6 nm recombination emission of O+ ions used to compute the nighttime ionospheric altitude distribution. ICON Far Ultra- Violet (FUV) imager is a Czerny–Turner design Spectrographic Imager with two exit slits and corresponding back imager cameras that produce two independent images in separate wavelength bands on two detectors. All observations will be processed as limb altitude profiles. In addition, the ionospheric 135.6 nm data will be processed as longitude and latitude spatial maps to obtain images of ion distributions around regions of equatorial spread F. The ICON FUV optic axis is pointed 20 degrees below local horizontal and has a steering mirror that allows the field of view to be steered up to 30 degrees forward and aft, to keep the local magnetic meridian in the field of view. The detectors are micro channel plate (MCP) intensified FUV tubes with the phosphor fiber-optically coupled to Charge Coupled Devices (CCDs). The dual stack MCP-s amplify the photoelectron signals to overcome the CCD noise and the rapidly scanned frames are co-added to digitally create 12-second integrated images. Digital on-board signal processing is used to compensate for geometric distortion and satellite motion and to achieve data compression. The instrument was originally aligned in visible light by using a special grating and visible cameras. Final alignment, functional and environmental testing and calibration were performed in a large vacuum chamber with a UV source. The test and calibration program showed that ICON FUV meets its design requirements and is ready to be launched on the ICON spacecraft. [less ▲]

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See detailCalibration and testing of wide-field UV instruments
Frey, Harald; Mende, Stephen; Loicq, Jerôme ULiege et al

in Journal of Geophysical Research. Space Physics (2017), 122

As with all optical systems the calibration of wide-field ultraviolet (UV) systems includes three main areas: sensitivity, imaging quality, and imaging capability. The one thing that makes UV calibrations ... [more ▼]

As with all optical systems the calibration of wide-field ultraviolet (UV) systems includes three main areas: sensitivity, imaging quality, and imaging capability. The one thing that makes UV calibrations difficult is the need for working in vacuum substantially extending the required time and effort compared to visible systems. In theory a ray tracing and characterization of each individual component of the optical system (mirrors, windows, and grating) should provide the transmission efficiency of the combined system. However, potentially unknown effects (contamination, misalignment, and measurement errors) can make the final error too large and unacceptable for most applications. Therefore, it is desirable to test and measure the optical properties of the whole system in vacuum and compare the overall response to the response of a calibrated photon detector. A proper comparison then allows the quantification of individual sources of uncertainty and ensures that the whole instrument performance is within acceptable tolerances or pinpoints which parts fail to meet requirements. Based on the experience with the IMAGE Spectrographic Imager, the Wide-band Imaging Camera, and the ICON Far Ultraviolet instruments, we discuss the steps and procedures for the proper radiometric sensitivity and passband calibration, spot size, imaging distortions, flatfield, and field of view determination. [less ▲]

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See detailConception of a near-infrared spectrometer for ground-based observations of massive stars
Kintziger, Christian ULiege; Desselle, Richard ULiege; Loicq, Jerôme ULiege et al

in Journal of Astronomical Telescopes, Instruments, and Systems (2017), 3(1), 015002

In our contribution, we outline the different steps in the design of a fiber-fed spectrographic instrument for stellar astrophysics. Starting from the derivation of theoretical relationships from the ... [more ▼]

In our contribution, we outline the different steps in the design of a fiber-fed spectrographic instrument for stellar astrophysics. Starting from the derivation of theoretical relationships from the scientific requirements and telescope characteristics, the entire optical design of the spectrograph is presented. Specific optical elements, such as a toroidal lens, are introduced to improve the instrument’s efficiency. Then the verification of predicted optical performances is investigated through optical analyses, such as resolution checking. [less ▲]

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See detailA 100 M GROUND RESOLUTION GLOBAL DAILY COVERAGE EARTH OBSERVATION MISSION
Loicq, Jerôme ULiege; Clermont, Lionel ULiege; Dierckx, Wouter et al

in Proceedings of SPIE: The International Society for Optical Engineering (2017), Proc. of SPIE Vol. 10563

PROBA-V has been successfully launched on 7th May 2013 and is providing a global monitoring in the continuity of the SPOT-VEGETATION mission. The progress in terms of ground resolution between Spot VGT ... [more ▼]

PROBA-V has been successfully launched on 7th May 2013 and is providing a global monitoring in the continuity of the SPOT-VEGETATION mission. The progress in terms of ground resolution between Spot VGT and PROBA-V is a factor 3 (1 km to 1/3 km ground resolution product). The User Community requirements for the next generation of global monitoring are a 100 m ground resolution product. This means an additional factor 3 improvement, but in a short time frame (5 years). After success of the PROBA-V mission, the Belgian Science Policy (BELSPO) initiates a PROBA-V Successor feasibility study. This study was undertaken by VITO and CSL to identify potential tracks to achieve a follow-on mission which is expected to be relevant for the User Community. The mission analyses for each of these tracks was evaluated. Today the PROBA-V mission lifetime is expected to expire by mid of 2018. Since the interest for global land monitoring is expected to continue in the future, this study proposes mission requirements and a shortlist of optimal mission scenarios for a follow-on mission in this short time frame. The goal of such a new PROBA-V mission is clear: it should ensure the data continuity of global vegetation monitoring, while taking the opportunity to further improve the data quality. Data continuity is essential for understanding long term trends of land use that may affect the global equilibrium of the planet (in the context of scarcity for land or food, natural disasters, climate change). As for added value, a fine example is the improvement of spatial resolution when comparing PROBA-V with the spatial resolution in SPOT-VEGETATION products. An improvement in spatial resolution towards a full 100m product is considered by the user community as the main target for a PROBA-V follow-on mission. [less ▲]

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See detailWaveguide solar concentrator design with spectrally separated light
Michel, Céline ULiege; Blain, Pascal ULiege; Clermont, Lionel ULiege et al

in Solar Energy (2017), 157

In this article, we propose a new solar concentrator based on spectral splitting of sunlight. Spectral splitting has the objective to collect different spectra onto spectrally adapted solar cells for a ... [more ▼]

In this article, we propose a new solar concentrator based on spectral splitting of sunlight. Spectral splitting has the objective to collect different spectra onto spectrally adapted solar cells for a more efficient use of the Sun’s spectrum. Its combination with solar concentration makes an alternative to classical technologies. The proposed concentrator is composed of a diffractive/refractive optical element that spectrally splits and focuses the light onto a waveguide. The light is then conducted by total internal reflection towards the two specific solar cells. The optical concept and optimization of each element is presented in this paper. An adaptation for dye sensitized solar cells is performed. A geometrical factor around 5× is reached. Finally, theoretical optical efficiency, the manufacturing process and experimental testing with a collimated Sun simulator are presented. [less ▲]

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