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Schmutz W.,PMOD WRC | Shapiro A.I.,PMOD WRC | Kretzschmar M.,University of Orléans | Zhukov A.N.,Moscow State University | And 2 more authors.
Solar Physics | Year: 2013

The Large Yield Radiometer (LYRA) is an XUV-EUV-MUV (soft X-ray to mid-ultraviolet) solar radiometer onboard the European Space Agency Project for On-Board Autonomy 2 (PROBA2) mission, which was launched in November 2009. LYRA acquires solar-irradiance measurements at a high cadence (nominally 20 Hz) in four broad spectral channels, from soft X-ray to MUV, which have been chosen for their relevance to solar physics, space weather, and aeronomy. We briefly review the design of the instrument, give an overview of the data products distributed through the instrument website, and describe how the data are calibrated. We also briefly present a summary of the main fields of research currently under investigation by the LYRA consortium. © 2013 Springer Science+Business Media Dordrecht.


Alexeenko I.,Institute For Technische Optik | Vandenrijt J.-F.,Center Spatial Of Liege | Georges M.,Center Spatial Of Liege | Pedrini G.,Institute For Technische Optik | And 3 more authors.
Applied Mechanics and Materials | Year: 2010

We show how digital holographic interferometry in the Long Wave InfraRed spectral range (LWIR) can be used for the investigation of mechanical structures. The 10.6 μm radiation is produced by a CO 2 Laser. Experimental results showing that the method can be used to locate defects in a panel are presented and advantages and disadvantages of this approach are discussed. © (2010) Trans Tech Publications, Switzerland.


Mathis F.,University of Liège | Bodu P.,French National Center for Scientific Research | Dubreuil O.,Center Spatial Of Liege | Salomon H.,University of Liège
Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms | Year: 2014

Les Bossats, near Ormesson, France, is a newly discovered late Mousterian open air site dated to around 47,000 years ago by thermoluminescence. The archaeological level, fossilized by loess, revealed a rich industry based on the discoid mode, associated with numerous fragments of red and yellow iron oxide-rich rocks showing clear traces of powder production (abrasion, striation, scraping), which are exceptional remains for this remote period. Archeological material and geological samples from the close environment were studied by PIXE and by petrographical observations made on thin sections. The geological sources were identified by means of PIXE analyses on two IBA facilities: AGLAE (2 MV tandem) at the C2RMF in Paris and the cyclotron of the IPNAS (University of Liège). We paid particular attention to the comparison of results obtained on both installations by using the same set of geological standards and by a fine evaluation of the limit of detection relative to each trace elements of interest for both experimental set ups. The elemental fingerprint of one geological source of iron-rich concretions corresponds clearly with the archaeological collection. At least, this investigation demonstrates that the colouring materials were minutely selected in the close neighbouring of the site by the Neanderthals. © 2014 Elsevier B.V. All rights reserved.


Mazy E.,Center Spatial of Liege | Hellin M.L.,Center Spatial of Liege
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2012

In the framework of instrument calibration, straylight issues are a critical aspect that can deteriorate the optical performances of instrument. To cope with this, a new facility is designed dedicated for in-field and far field straylight characterization: up to 10-8 for in-field and up to 10-10 for far field straylight in the visible to NIR spectral ranges. Moreover, from previous straylight test performed at CSL, vacuum conditions are needed for reaching the 10-10 rejection requirement mainly to avoid air/dust diffusion. The major constrains are to design a straylight facility either for in-field and out-field straylight measurements. That requires high dynamic range at source level and a high radiance point source allowing small diverging collimated beam. Moreover, the straylight facility has to be implemented into a limited envelope and has to be built with vacuum compatible materials and black coating. As checking the facility performance requires an instrument better than the facility itself, that is no easy to find, so that the performances have been estimated through a modelisation into a non sequential optical software. This modelisation is based on CAD importation of mechanical design, on BRDF characteristics of black coating and on statistical averaging of ray tracing at instrument entrance. © 2012 SPIE.


De Rauw D.,Center Spatial Of Liege | Barbier C.,Center Spatial Of Liege
2014 International Radar Conference, Radar 2014 | Year: 2014

Multi-Chromatic or spectral Analysis (MCA) of SAR images consists in splitting wide band SAR signals into sub-bands to generate several lower resolution images from a single acquisition. This splitting allows performing a spectral analysis of observed scatterers. Spectral coherence is derived by computing the coherence between sub-images issued from a single SAR acquisition. It was shown that in the presence of a random distribution of surface scatterers, spectral coherence is proportional to sub-band intersection of sub-images. This model is fully verified when observing spectral coherence on open seas areas. If the scatterers distribution departs from this distribution, like for manmade structures, spectral coherence may be preserved to a certain degree. We investigated the spectral coherence to perform vessel detection on a sea background by using spotlight images acquired on the Venice Lagoon. Sea background tends to lead to very low spectral coherence while this latter is preserved on the targeted vessels, even for very small ones. A first analysis shows that all vessels observable in intensity images are easily detected in the spectral coherence images which can be used as a complementary information channel to constrain vessel detection © 2014 IEEE.


Derauw D.,Center Spatial Of Liege | Derauw D.,Belgium Royal Military Academy | Orban A.,Center Spatial Of Liege | Barbier C.,Center Spatial Of Liege
Remote Sensing Letters | Year: 2010

Range resolution of SAR images is determined by transmitted radar signal bandwidth. Most recent SAR sensors use wide band signals in order to achieve metric range resolution, whereas metric azimuth resolution can be achieved in spotlight mode. As an example, ENVISAT ASAR sensor uses a 15-MHz bandwidth chirp whereas TerraSAR-X spotlight mode uses signals having a 150-MHz bandwidth leading to a potentially 10 times higher resolution. One can also take advantage of wide band to split the full band into sub-bands and generate several lower resolution images from a single acquisition, each being centred on slightly different frequencies. These sub-images can then be used in a classical interferometric process to measure inter-band coherence of a given scene. This inter-band coherence reveals scatterers keeping a stable-phase behaviour along with frequency shift. A simple coherence model derived from Zebker model for randomly distributed surface scatterers is proposed. Examples are presented, showing that scatterers can have a behaviour that deviates from the model, leading to a new information channel.


Michel C.,Center Spatial Of Liege | Loicq J.,Center Spatial Of Liege | Languy F.,University of Liège | Habraken S.,Center Spatial Of Liege | Habraken S.,University of Liège
Solar Energy Materials and Solar Cells | Year: 2014

This paper presents a new design of a planar solar concentrator for space applications. The concentrator focuses light onto two spatially separated photovoltaic cells, allowing for independent control of the output power of each cell. Thanks to a blazed diffraction grating superimposed on a Fresnel lens, advantages of both spectral splitting and light focusing can be combined. The theoretical model of the optical design is presented, with the optimization of either element. Moreover, configuration improvement is proposed: a symmetrical configuration composed of two lenses. First numerical results are presented, highlighting the possibility to design a concentrator at about 10× for each cell, with an optical efficiency of about 75% and less than 10% of losses for tracking errors lower than ±0.9 © 2013 Elsevier B.V.


Roose S.,Center Spatial Of Liege | Stockman Y.,Center Spatial Of Liege | Sodnik Z.,European Space Agency
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2013

The Coarse Lateral Sensor (CLS) is a system able to measure the lateral position between two satellites. It bridges the gap between the coarse alignment accuracy achievable with radio frequency metrology or global positioning systems (GPS), and the alignment accuracy required to start higher-precision optical metrology systems based on interferometry. The system is a standalone unit. Once connected to an unregulated 28V power-supply, it delivers, the lateral position of a corner cube retro-reflector and tracks this position at a rate of 10 Hz. The system is operational with the sun in its field-of-view. The coarse lateral sensor has successfully undergone thermal qualification (40 C and -30 °C), and vibration test (highlevel sinus, random and shock test in the 3-axis). © 2013 SPIE.


Simar J.F.,Center Spatial Of Liege | Stockman Y.,Center Spatial Of Liege | Surdej J.,University of Liège
Applied Optics | Year: 2015

Space observations of fainter and more distant astronomical objects constantly require telescope primary mirrors with larger sizes. The diameters of monolithic primary mirrors are restricted to 10 m because of manufacturing limitations. For space telescopes, the primary mirrors are limited to less than 5 m due to fairing capacity. Segmented primary mirrors thus constitute an alternative solution to deal with the steady increase of primary mirror size. The optical path difference between the individual segments must be close to 0 (a few nanometers) in order to be diffraction-limited. In this paper, we propose a new intersegment piston sensor based on the coherence measurement of a star image. This sensor is intended to be used in the co-phasing system of future segmented mirrors. © 2015 Optical Society of America.


Languy F.,University of Liège | Lenaerts C.,Center Spatial Of Liege | Loicq J.,Center Spatial Of Liege | Thibert T.,Center Spatial Of Liege | Habraken S.,University of Liège
Solar Energy Materials and Solar Cells | Year: 2013

A primary optics for solar concentrator made of an achromatic Fresnel doublet has been designed and manufactured. The achromatic Fresnel doublet combines the advantages of plastic lenses without being affected by chromatic aberrations. The performance has been determined experimentally using a homemade continuous solar simulator and compared to paraxial theory and ray-tracing simulations. Experimental results are in good agreement with theory and show that the achromatic Fresnel doublet is tolerant to manufacturing errors and uncertainty on the dispersion of the refractive index: the concentration factor remains above 1600× with an f-number of 2. © 2012 Elsevier B.V. All rights reserved.

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