Gaia Data Release 2 Hambly, N. C.; Cropper, M.; Boudreault, S. ...
Astronomy and astrophysics (Berlin),
08/2018, Letnik:
616
Journal Article
Recenzirano
Odprti dostop
Context.
The European Space Agency’s
Gaia
satellite was launched into orbit around L2 in December 2013. This ambitious mission has strict requirements on residual systematic errors resulting from ...instrumental corrections in order to meet a design goal of sub-10 microarcsecond astrometry. During the design and build phase of the science instruments, various critical calibrations were studied in detail to ensure that this goal could be met in orbit. In particular, it was determined that the video-chain offsets on the analogue side of the analogue-to-digital conversion electronics exhibited instabilities that could not be mitigated fully by modifications to the flight hardware.
Aims.
We provide a detailed description of the behaviour of the electronic offset levels on short (<1 ms) timescales, identifying various systematic effects that are known collectively as “offset non-uniformities”. The effects manifest themselves as transient perturbations on the gross zero-point electronic offset level that is routinely monitored as part of the overall calibration process.
Methods.
Using in-orbit special calibration sequences along with simple parametric models, we show how the effects can be calibrated, and how these calibrations are applied to the science data. While the calibration part of the process is relatively straightforward, the application of the calibrations during science data processing requires a detailed on-ground reconstruction of the readout timing of each charge-coupled device (CCD) sample on each device in order to predict correctly the highly time-dependent nature of the corrections.
Results.
We demonstrate the effectiveness of our offset non-uniformity models in mitigating the effects in
Gaia
data.
Conclusions.
We demonstrate for all CCDs and operating instrument/modes on board
Gaia
that the video-chain noise-limited performance is recovered in the vast majority of science samples.
Gaia Data Release 2 Hambly, N. C.; Cropper, M.; Boudreault, S. ...
Astronomy & astrophysics,
08/2018, Letnik:
616
Journal Article
Recenzirano
Odprti dostop
Context. The European Space Agency’s Gaia satellite was launched into orbit around L2 in December 2013. This ambitious mission has strict requirements on residual systematic errors resulting from ...instrumental corrections in order to meet a design goal of sub-10 microarcsecond astrometry. During the design and build phase of the science instruments, various critical calibrations were studied in detail to ensure that this goal could be met in orbit. In particular, it was determined that the video-chain offsets on the analogue side of the analogue-to-digital conversion electronics exhibited instabilities that could not be mitigated fully by modifications to the flight hardware. Aims. We provide a detailed description of the behaviour of the electronic offset levels on short (<1 ms) timescales, identifying various systematic effects that are known collectively as “offset non-uniformities”. The effects manifest themselves as transient perturbations on the gross zero-point electronic offset level that is routinely monitored as part of the overall calibration process. Methods. Using in-orbit special calibration sequences along with simple parametric models, we show how the effects can be calibrated, and how these calibrations are applied to the science data. While the calibration part of the process is relatively straightforward, the application of the calibrations during science data processing requires a detailed on-ground reconstruction of the readout timing of each charge-coupled device (CCD) sample on each device in order to predict correctly the highly time-dependent nature of the corrections. Results. We demonstrate the effectiveness of our offset non-uniformity models in mitigating the effects in Gaia data. Conclusions. We demonstrate for all CCDs and operating instrument/modes on board Gaia that the video-chain noise-limited performance is recovered in the vast majority of science samples.
Emission times of proton-induced traps and optical spot profiles have been measured at temperatures around -110/spl deg/C for large format charge-coupled devices (CCDs), representative of those to be ...used for the Gaia mission. There are at least seven trap species involved, with emission times in the range 0.3 /spl mu/s to 130 s and there is evidence for charge re-trapping by fast traps. Trap filling using a charge injection gate is discussed.
The European Space Agency Gaia satellite was launched into orbit around L2 in December 2013. This ambitious mission has strict requirements on residual systematic errors resulting from instrumental ...corrections in order to meet a design goal of sub-10 microarcsecond astrometry. During the design and build phase of the science instruments, various critical calibrations were studied in detail to ensure that this goal could be met in orbit. In particular, it was determined that the video-chain offsets on the analogue side of the analogue-to-digital conversion electronics exhibited instabilities that could not be mitigated fully by modifications to the flight hardware. We provide a detailed description of the behaviour of the electronic offset levels on microsecond timescales, identifying various systematic effects that are known collectively as offset non-uniformities. The effects manifest themselves as transient perturbations on the gross zero-point electronic offset level that is routinely monitored as part of the overall calibration process. Using in-orbit special calibration sequences along with simple parametric models, we show how the effects can be calibrated, and how these calibrations are applied to the science data. While the calibration part of the process is relatively straightforward, the application of the calibrations during science data processing requires a detailed on-ground reconstruction of the readout timing of each charge-coupled device (CCD) sample on each device in order to predict correctly the highly time-dependent nature of the corrections. We demonstrate the effectiveness of our offset non-uniformity models in mitigating the effects in Gaia data. We demonstrate for all CCDs and operating instrument and modes on board Gaia that the video-chain noise-limited performance is recovered in the vast majority of science samples.
This paper discusses the modalities of learning among young users of digitalinterfaces. Following Auray (2016), we deepen the analysis of skills to masterdigital environments by taking up and ...discussing the 4 skills typology heelaborates. Among them, the geographical one gathers 2 sub-skills: thetopological one, a tactical action adjusted from near to near and the cartographicone, a strategic and overhanging action taking account of exhaustive knowledgeon a situation. In order to carry out this comparative work, we cross-referencelearning in two institutionalized fields: university and health. Empirical datafrom two surveys conducted in these contexts make it possible to complete theanalysis of social inequalities toward digital technology with that of cognitivedisabilities related to autism and physical disabilities related to chronic pain.
Cette contribution questionne les modalités d'apprentissage des jeunes utilisateurs d'interfaces numériques. À la suite d'Auray (2016), nous analysons les aptitudes à maîtriser les environnements numériques, en discutant la typologie en 4 compétences qu'il propose. Parmi elles, nous nous focalisions surtout sur la compétence dite géographique. Elle regroupe 2 sous-compétences : topologique, une position d'action tactique réorientée de proche en proche et cartographique, une position d'action stratégique et surplombante envisagée en présence de connaissances exhaustives sur une situation. Pour mener ce travail comparatif, nous croisons les apprentissages inscrits dans deux domaines institutionnalisés : l'université et la santé. Des données empiriques issues de deux enquêtes menées dans ces contextes permettent de compléter l'analyse des inégalités sociales face au numérique par celle des handicaps cognitifs liés à l'autisme et physiques liés à des douleurs chroniques.
Cette investigation caractérise les opérations de cadrages, telles qu’elles sont décrites par Goffman, afin de documenter précisément les arnaques subies lors d’échanges marchands d’objets virtuels ...au sein d’un jeu en ligne. L’enjeu est de montrer les apports et les limites de ces cadrages pour expliquer la situation confrontationnelle d’une arnaque. Une ethnographie du virtuel (Hine, 2000) du jeu Dofus nous permet d’appréhender cette situation à partir d’une théorie pragmatique des affects attentive à des contextes sociotechniques élargis, ceci afin de reconnecter les cadrages dans un jeu en ligne à des enjeux de design et de morale.
Branched structures are present in a diverse set of problems, from modeling branch pipe connections to simulating tree dynamics. Soft corals like the Bipinnate sea plume, have a branched geometry and ...are soft enough to bend under the waves. Due to their circular cross section, a vortex street forms in the coral’s wake inducing vibrations of its branches. Despite extensive studies on VIV in straight geometries, the three-dimensional (3D) dynamics of flexible branched structures remains uninvestigated. In this numerical and experimental study, we develop a novel formulation for the accurate computation of in-line and cross-flow VIV of frame structures undergoing large deformation. The finite element approach is used to model arbitrarily complex geometries of branched frame structures. Our formulation allows to model complex geometries with forks or sharp angles. The consistent 3D corotational formulation for frame elements computes the internal, inertial and hydrodynamic forces. A wake-oscillator approach models the near wake dynamics with fluctuating fluid forces on the structure in the in-line and cross-flow directions. The drag and lift coefficients follow distributed Van der Pol oscillators. Moreover, we implement the numerical resolution procedure in the open-source library ONSAS. The present formulation and numerical resolution procedure is validated by solving three examples, including comparisons with an analytical solution, a wake-oscillator, and experimental data from the literature. We also conduct experiments of a flexible and elastic cylinder clamped inside a water tunnel under a constant uniform flow. Amplitudes and power spectral density of the tip transverse displacements are compared with the model prediction. Finally, the proposed formulation is applied on a cylinder with two branches. The simulations demonstrate a multi-frequency response with higher amplitudes of displacements when additional branches are incorporated onto the cylinder, emphasizing the significance of considering VIV in nature and engineering applications for such geometries.
Le jeu au prisme de la matérialité Vétel, Bruno; Turquier, Barbara
Tracés (Lyons, France),
05/2015, Letnik:
1, Številka:
28
Journal Article
Recenzirano
Odprti dostop
Le jeu a été généralement étudié au regard des règles, de l'imaginaire ou de la narration ludiques. Aujourd'hui les dimensions tangibles du jeu bénéficient d'un nouvel intérêt, auquel ce numéro de ...Tracés entend contribuer. Il accueille des approches et disciplines diverses s'intéressant au rôle de la matérialité, explorant la complexité de la notion ainsi que les limites de sa vertu heuristique. Les textes interrogent le rapport entre le jeu et la notion de matérialité, prise dans une acception large qui intègre les matériaux de confection, les objets, les interfaces et infrastructures, ainsi que les dimensions corporelles indissociables du jeu. Elles font apparaître des enjeux industriels, politiques, esthétiques et symboliques, et permettent de repenser les finalités non ludiques parfois assignées aux jeux. Les textes montrent aussi que les éléments tangibles jouent un rôle décisif dans l'engagement des joueurs et contribuent à délimiter les contours des expériences ludiques, autant qu'à créer et à maintenir une forme de contrat social partagé par les joueurs.
Context The European Space Agency's Gaia satellite was launched into orbit around L2 in December 2013. This ambitious mission has strict requirements on residual systematic errors resulting from ...instrumental corrections in order to meet a design goal of sub-10 microarcsecond astrometry. During the design and build phase of the science instruments, various critical calibrations were studied in detail to ensure that this goal could be met in orbit. In particular, it was determined that the video-chain offsets on the analogue side of the analogue-to-digital conversion electronics exhibited instabilities that could not be mitigated fully by modifications to the flight hardware. Aims We provide a detailed description of the behaviour of the electronic offset levels on short (<<1 ms) timescales, identifying various systematic effects that are known collectively as 'offset non-uniformities'. The effects manifest themselves as transient perturbations on the gross zero-point electronic offset level that is routinely monitored as part of the overall calibration process. Methods Using in-orbit special calibration sequences along with simple parametric models, we show how the effects can be calibrated,and how these calibrations are applied to the science data. While the calibration part of the process is relatively straightforward, the application of the calibrations during science data processing requires a detailed on-ground reconstruction of the readout timing of each charge-coupled device (CCD) sample on each device in order to predict correctly the highly time-dependent nature of the corrections. Results We demonstrate the effectiveness of our offset non-uniformity models in mitigating the effects in Gaia data. Conclusions We demonstrate for all CCDs and operating instrumentmod es on board Gaia that the video-chain noise-limited performance is recovered in the vast majority of science sample
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