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Gaia Data Release 2. Calibration and mitigation of electronic offset effects in the data

Research output: Contribution to journalArticle

  • Mark Cropper
  • Steve Boudreault (Member of Consortium)
  • Cian Crowley
  • Ralf Kohley (Member of Consortium)
  • Jos de Bruijne (Member of Consortium)
  • Chris Dolding (Member of Consortium)
  • Claus Fabricius
  • George seabroke
  • Nicholas Rowell (Member of Consortium)
  • Juanma Fleitas (Member of Consortium)
  • Steven Baker (Member of Consortium)
  • Mike Smith (Member of Consortium)
  • Paola Satoretti (Member of Consortium)
  • Olivier Marchal (Member of Consortium)
  • David Katz (Member of Consortium)
  • Francesca de Angeli (Member of Consortium)
  • Giorgia Busso (Member of Consortium)
  • Marco Riello (Member of Consortium)
  • Carlos Allende Prieto (Member of Consortium)
  • Sebastian Els (Member of Consortium)
  • Leonardo Corcione (Member of Consortium)
  • Eduardo Masana (Member of Consortium)
  • Xavier Luri (Member of Consortium)
  • F Chassat
  • F Fusero
  • J Pasquier (Member of Consortium)
  • C Vetel (Member of Consortium)
  • G Sarri (Member of Consortium)
  • P Gare (Member of Consortium)

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Original languageEnglish
JournalAstronomy & astrophysics
DOIs
Publication statusPublished - 27 Apr 2018

Abstract

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 (<<1ms) 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.

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