Last 7 days
Bookmark and Share    
Full Text
See detailOPSE metrology system onboard of the PROBA3 mission of ESA
Loreggia, D.; Bemporad, A.; Capobianco, G. et al

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

In recent years, ESA has assessed several mission involving formation flying (FF). The great interest in this topics is mainly driven by the need for moving from ground to space the location of next ... [more ▼]

In recent years, ESA has assessed several mission involving formation flying (FF). The great interest in this topics is mainly driven by the need for moving from ground to space the location of next generation astronomical telescopes overcoming most of the critical problems, as example the construction of huge baselines for interferometry. In this scenario, metrology systems play a critical role. PROBA3 is an ESA technology mission devoted to in-orbit demonstration of the FF technique, with two satellites, an occulter and a main satellite housing a coronagraph named ASPIICS, kept at an average inter-distance by about 144m, with micron scale accuracy. The guiding proposal is to test several metrology solution for spacecraft alignment, with the important scientific return of having observation of Corona at never reached before angular field. The Shadow Position Sensors (SPS), and the Optical Position Emitters Sensors (OPSE) are two of the systems used for FF fine tracking. The SPS are finalized to monitor the position of the two spacecraft with respect to the Sun and are discussed in dedicated papers presented in this conference. The OPSE will monitor the relative position of the two satellites and consists of 3 emitters positioned on the rear surface of the occulter, that will be observed by the coronagraph itself. By following the evolution of the emitters images at the focal plane the alignment of the two spacecrafts is retrieved via dedicated centroiding algoritm. We present an overview of the OPSE system and of the centroiding approach. [less ▲]

Detailed reference viewed: 16 (4 ULg)
Full Text
See detailThe Shadow Positioning Sensors (SPS) for formation flying metrology on-board the ESA-PROBA3 mission
Bemporad, A.; Baccani, C.; Capobianco, G. et al

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

PROBA3 is an ESA technology mission devoted to in-orbit demonstration of the formation flight (FF) technique, with two satellites kept at an average inter-distance by about 144 m. The ASPIICS instrument ... [more ▼]

PROBA3 is an ESA technology mission devoted to in-orbit demonstration of the formation flight (FF) technique, with two satellites kept at an average inter-distance by about 144 m. The ASPIICS instrument on-board PROBA3 will be the first ever space-based coronagraph working on one satellite and having the external occulter located on the second satellite, thus allowing observations of the inner solar corona with unprecedented reduction of stray light. During the observational periods, the FF configuration will be maintained with very high precision and two different techniques will be implemented: the use of Shadow Positioning Sensors (SPS) located on the Coronagraph Spacecraft (diodes measuring the penumbral light intensity on the entrance pupil plane) and the use of Occulter Position Sensor LEDs (OPSE) located on the back side of the Occulter Spacecraft. This paper will review the main instrumental requirements on the SPS needed to determine the 3-dimensional relative positioning of the two PROBA3 satellites with the high precision and frequency. [less ▲]

Detailed reference viewed: 19 (5 ULg)
Full Text
See detailFormation flying metrology for the ESA-PROBA3 mission: the Shadow Position Sensors (SPS) silicon photomultipliers (SiPMs) readout electronics
Focardi, M.; Bemporad, A.; Buckley, S. et al

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

The European Space Agency (ESA) is planning to launch in 2018 the PROBA3 Mission, designed to demonstrate the inorbit formation flying (FF) attitude capability of its two satellites and to observe the ... [more ▼]

The European Space Agency (ESA) is planning to launch in 2018 the PROBA3 Mission, designed to demonstrate the inorbit formation flying (FF) attitude capability of its two satellites and to observe the inner part of the visible solar corona as the main scientific objective. The solar corona will be observed thanks to the presence on the first satellite, facing the Sun, of an external occulter producing an artificial eclipse of the Sun disk. The second satellite will carry on the coronagraph telescope and the digital camera system in order to perform imaging of the inner part of the corona in visible polarized light, from 1.08 Rsun up to about 3 Rsun. One of the main metrological subsystems used to control and to maintain the relative (i.e. between the two satellites) and absolute (i.e. with respect to the Sun) FF attitude is the Shadow Position Sensor (SPS) assembly. It is composed of eight micro arrays of silicon photomultipliers (SiPMs) able to measure with the required sensitivity and dynamic range the penumbral light intensity on the Coronagraph entrance pupil. In the following of the present paper we describe the overall SPS subsystem and its readout electronics with respect to the capability to satisfy the mission requirements, from the light conversion process on board the silicon-based SPS devices up to the digital signal readout and sampling. [less ▲]

Detailed reference viewed: 17 (5 ULg)
Full Text
See detailDesign and modelisation of ASPIICS optics
Galy, Camille ULg; 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 ▲]

Detailed reference viewed: 31 (16 ULg)
Full Text
See detailSignificance of the occulter diffraction for the PROBA3/ASPIICS formation flight metrology
Landini, F.; Bemporad, A.; Focardi, M. et al

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

PROBA-3/ASPIICS is a formation Flying coronagraph selected by ESA and currently in its C/D phase. It is constituted by two spacecrafts (OSC, Occulter SpaceCraft, carrying the occulter, diameter 142 cm ... [more ▼]

PROBA-3/ASPIICS is a formation Flying coronagraph selected by ESA and currently in its C/D phase. It is constituted by two spacecrafts (OSC, Occulter SpaceCraft, carrying the occulter, diameter 142 cm, and CSC, Coronagraph SpaceCraft, with the telescope) separated by ~144 m, kept in strict alignment by means of an active custom system. The alignment active system most critical components are the Shadow Positioning Sensors (SPS), a series of Si-PM (Silicon Photomultiplier) measuring the penumbra generated by the occulter. The arrangement of the SPSs around the telescope entrance aperture is defined as a trade-off between mechanical constraints and maximum sensitivity to misalignments. The signal detected by the SPSs can be approximately simulated with a geometrical analysis based on the variation of the penumbra generated by the external occulter. The stray light generated by the diffraction from the external occulter may affect the SPSs signal. It is mandatory to carefully evaluate its level in order to refine the active alignment adjustment algorithm. This work is dedicated to the description of the preliminary investigation performed in order to evaluate the impact of the diffraction on the SPSs signal. [less ▲]

Detailed reference viewed: 14 (4 ULg)
Full Text
See detailDesign status of ASPIICS, an externally occulted coronagraph for PROBA-3
Renotte, Etienne ULg; Alia, A.; Bemporad, A. et al

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

The “sonic region” of the Sun corona remains extremely difficult to observe with spatial resolution and sensitivity sufficient to understand the fine scale phenomena that govern the quiescent solar corona ... [more ▼]

The “sonic region” of the Sun corona remains extremely difficult to observe with spatial resolution and sensitivity sufficient to understand the fine scale phenomena that govern the quiescent solar corona, as well as phenomena that lead to coronal mass ejections (CMEs), which influence space weather. Improvement on this front requires eclipse-like conditions over long observation times. The space-borne coronagraphs flown so far provided a continuous coverage of the external parts of the corona but their over-occulting system did not permit to analyse the part of the white-light corona where the main coronal mass is concentrated. The proposed PROBA-3 Coronagraph System, also known as ASPIICS (Association of Spacecraft for Polarimetric and Imaging Investigation of the Corona of the Sun), with its novel design, will be the first space coronagraph to cover the range of radial distances between ~1.15 and 3 solar radii where the magnetic field plays a crucial role in the coronal dynamics, thus providing continuous observational conditions very close to those during a total solar eclipse. PROBA-3 is first a mission devoted to the in-orbit demonstration of precise formation flying techniques and technologies for future European missions, which will fly ASPIICS as primary payload. The instrument is distributed over two satellites flying in formation (approx. 150m apart) to form a giant coronagraph capable of producing a nearly perfect eclipse allowing observing the sun corona closer to the rim than ever before. The coronagraph instrument is developed by a large European consortium including about 20 partners from 7 countries under the auspices of the European Space Agency. This paper is reviewing the recent improvements and design updates of the ASPIICS instrument as it is stepping into the detailed design phase. [less ▲]

Detailed reference viewed: 43 (17 ULg)
Full Text
See detailCeci n’est pas un conseil !
Choffray, Jean-Marie ULg

E-print/Working paper (2015)

La « Grande Récession de 2008 » a un mérite. Un seul ! Elle a rendu public le fait que personne ne savait exactement ce qui s’était passé, ni ce qui se passait. Pourquoi une telle crise de confiance avait ... [more ▼]

La « Grande Récession de 2008 » a un mérite. Un seul ! Elle a rendu public le fait que personne ne savait exactement ce qui s’était passé, ni ce qui se passait. Pourquoi une telle crise de confiance avait-elle vu le jour ? Quelles en seraient les conséquences ? Toutes et tous se sont trompés, y compris les meilleurs. Même celles et ceux qui étaient convaincus d’avoir raison ! Plus que jamais, l’incertitude, la saine et souveraine incertitude, garantit la liberté de l’investisseur... et du professeur ! [less ▲]

Detailed reference viewed: 1937 (122 ULg)
Full Text
See detailArabie saoudite et Etats-Unis: un divorce annoncé
Hermans, Michel ULg; Ernst, Damien ULg

Article for general public (2015)

Detailed reference viewed: 121 (11 ULg)
See detailPathways of recurrent high-grade squamous intraepithelial lesions of the cervix
Herfs, Michael ULg

Conference (2015, September 20)

Detailed reference viewed: 9 (1 ULg)
Full Text
See detailMarkets flash graphs
Choffray, Jean-Marie ULg

E-print/Working paper (2015)

A graph is worth a hundred words... A good graph may suggest some new heuristics. And…, a series of excellent graphs may provide the backbone of a theory! The goal of this paper is to share a set of ... [more ▼]

A graph is worth a hundred words... A good graph may suggest some new heuristics. And…, a series of excellent graphs may provide the backbone of a theory! The goal of this paper is to share a set of graphs from multiple sources that offer as many flashes on current and past market conditions. Inevitably, these graphs reflect my own biases and questionings. They are not meant to induce any action aside, maybe, from their integration in a personal Information System. The Great Recession of 2008, whose consequences are still unfolding, has been for each of us a powerful invitation to modesty. We live in a world where improbable, unthinkable and impossible events happen every day... More than ever, it’s time to sit down, shut up, watch out, build graphs, and think… hard! [less ▲]

Detailed reference viewed: 195 (30 ULg)
See detailLa consultation pour troubles du comportement à l'adolescence : importance du timing pubertaire
Glowacz, Fabienne ULg

Scientific conference (2015, September 19)

Detailed reference viewed: 13 (0 ULg)
Peer Reviewed
See detailNon-invasive markers: the role of G-CSF?
Munaut, Carine ULg

Conference (2015, September 19)

Detailed reference viewed: 4 (0 ULg)
Full Text
Peer Reviewed
See detailEFFECT OF TRUNK MOTOR CONTROL TRAINING IN ELITE SOCCER PLAYERS WITH LOW BACK PAIN
GROSDENT, Stéphanie ULg; Demoulin, Christophe ULg; Rodriguez de la Cruz, Carlos ULg et al

Poster (2015, September 18)

Background and aims: The purpose of this study was to examine the effect of a motor control training program on the lumbopelvic motor control (LMC) in elite soccer players with a history of low back pain ... [more ▼]

Background and aims: The purpose of this study was to examine the effect of a motor control training program on the lumbopelvic motor control (LMC) in elite soccer players with a history of low back pain (LBP). Methods: Twenty-four male elite soccer players (mean age of 18.3 years) filled in questionnaires related to LBP and were divided into two groups: 12 players with a history of LBP (LBP group) and 12 players without a history of LBP (no LBP group). Then, they performed five LMC tests [the Bent Knee Fall Out test (BKFO), the Knee Lift Abdominal Test (KLAT), the Sitting Knee Extension Test (SKET), the Waiter’s Bow (WB) and the test of the transversus abdominis (TrA)] which were conducted and scored (0=failed, 1=correct) by a physiotherapist, blinded to the medical history of the participants. The total LMC score (ranging from 0 to 5) was calculated by adding the score at each test. During the following 10 weeks, the no LBP group conducted a soccer training as usual while LBP group performed an additional specific core stability program (1h/week). Results: At baseline, the participants of the LBP group had a worse LMC than the no LBP group (mean LMC score of 1.1 vs 3.1, p<0.01). The between-groups difference was particularly marked for the BKFO (p<0.01), KLAT (p<0.01) and SKET (p<0.05) tests. At the end of the intervention program, the LMC score of the players with a history of LBP increased significantly (p<0.0001) and was similar to the score of the players without a history of LBP (mean LMC score of 3.2 vs 3.3, p=1.00). Conclusions: LMC can be decreased in elite active soccer players with a history of LBP. Specific core stability program is effective to improve LMC in these players. [less ▲]

Detailed reference viewed: 79 (4 ULg)
Full Text
See detailThe importance of physical educators’ representations about physical activity
Cloes, Marc ULg

Conference (2015, September 18)

Physical education (PE) teachers need to develop clear representaitons about physical activity (PA). In fact, they have to promote an active lifestyle among their pupils/students and it will not be ... [more ▼]

Physical education (PE) teachers need to develop clear representaitons about physical activity (PA). In fact, they have to promote an active lifestyle among their pupils/students and it will not be possible without developing an extended knowledge about physical activity. This presentation has been designed in order to make the PE teachers and their trainers that their representations about PA could be worse than they believe. Moreover, the interactive way of this presentation will provide an interesting example of an approach that could be used on the field. [less ▲]

Detailed reference viewed: 41 (2 ULg)
See detailEntre sympathie pour la cause et passage à l'acte: analyse du processus de dérive radicale
Garcet, Serge ULg

Scientific conference (2015, September 18)

Detailed reference viewed: 21 (2 ULg)
See detailImpact des attentes identitaires sur la nature de l'engagement individuel et la radicalisation
Garcet, Serge ULg

Scientific conference (2015, September 18)

Detailed reference viewed: 41 (3 ULg)
Full Text
See detailInnovation in Veterinary Education. Innovative tools to teach pregnancy and parturition in the horse.
Hanzen, Christian ULg; Govaere, Jan

Conference (2015, September 18)

Detailed reference viewed: 77 (2 ULg)
See detailNid de coucou. De quelques performances filmées dans l'espace public.
Hamers, Jérémy ULg

Conference (2015, September 18)

Detailed reference viewed: 22 (1 ULg)