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The impact of CCD radiation damage on Gaia astrometry - II. Effect of image location errors on the astrometric solution

Holl, Berry LU ; Prod'homme, T.; Lindegren, Lennart LU and Brown, A. G. A. (2012) In Monthly Notices of the Royal Astronomical Society 422(4). p.2786-2807
Abstract
Gaia, the next astrometric mission of the European Space Agency, will use a camera composed of 106 CCDs to collect multiple observations for one billion stars. The astrometric core solution of Gaia will use the estimated location of the stellar images on the CCDs to derive the astrometric parameters (position, parallax and proper motion) of the stars. The Gaia CCDs will suffer from charge transfer inefficiency (CTI) mainly caused by radiation damage. CTI is expected to significantly degrade the quality of the collected images which ultimately affects the astrometric accuracy of Gaia. This paper is the second and last in a study aiming at characterizing and quantifying the impact of CCD radiation damage on Gaia astrometry. Here we focus on... (More)
Gaia, the next astrometric mission of the European Space Agency, will use a camera composed of 106 CCDs to collect multiple observations for one billion stars. The astrometric core solution of Gaia will use the estimated location of the stellar images on the CCDs to derive the astrometric parameters (position, parallax and proper motion) of the stars. The Gaia CCDs will suffer from charge transfer inefficiency (CTI) mainly caused by radiation damage. CTI is expected to significantly degrade the quality of the collected images which ultimately affects the astrometric accuracy of Gaia. This paper is the second and last in a study aiming at characterizing and quantifying the impact of CCD radiation damage on Gaia astrometry. Here we focus on the effect of the image location errors induced by CTI on the astrometric solution. We apply the Gaia Astrometric Global Iterative Solution (AGIS) to simulated Gaia-like observations for 1 million stars including CTI-induced errors as described in the first paper. We show that a magnitude-dependent image location bias is propagated in the astrometric solution, biasing the estimation of the astrometric parameters as well as decreasing its precision. We demonstrate how the Gaia scanning law dictates this propagation and the ultimate sky distribution of the CTI-induced errors. The possibility of using the residuals of the astrometric solution to improve the calibration of the CTI effects is investigated. We also estimate the astrometric errors caused by (faint) disturbing stars preceding the stellar measurements on the CCDs. Finally, we show that, for single stars, the overall astrometric accuracy of Gaia can be preserved to within 10 per cent of the CTI-free case for all magnitudes by appropriate modelling at the image location estimation level and using the solution residuals. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
instrumentation: detectors, methods: analytical, methods: numerical, space vehicles, astrometry
in
Monthly Notices of the Royal Astronomical Society
volume
422
issue
4
pages
2786 - 2807
publisher
Wiley-Blackwell
external identifiers
  • wos:000304246100004
  • scopus:84861234298
ISSN
1365-2966
DOI
10.1111/j.1365-2966.2012.20429.x
language
English
LU publication?
yes
id
ee5a1fca-6255-4d0b-8708-444ab94c6cb8 (old id 2799748)
date added to LUP
2012-06-25 11:27:05
date last changed
2017-01-08 03:16:38
@article{ee5a1fca-6255-4d0b-8708-444ab94c6cb8,
  abstract     = {Gaia, the next astrometric mission of the European Space Agency, will use a camera composed of 106 CCDs to collect multiple observations for one billion stars. The astrometric core solution of Gaia will use the estimated location of the stellar images on the CCDs to derive the astrometric parameters (position, parallax and proper motion) of the stars. The Gaia CCDs will suffer from charge transfer inefficiency (CTI) mainly caused by radiation damage. CTI is expected to significantly degrade the quality of the collected images which ultimately affects the astrometric accuracy of Gaia. This paper is the second and last in a study aiming at characterizing and quantifying the impact of CCD radiation damage on Gaia astrometry. Here we focus on the effect of the image location errors induced by CTI on the astrometric solution. We apply the Gaia Astrometric Global Iterative Solution (AGIS) to simulated Gaia-like observations for 1 million stars including CTI-induced errors as described in the first paper. We show that a magnitude-dependent image location bias is propagated in the astrometric solution, biasing the estimation of the astrometric parameters as well as decreasing its precision. We demonstrate how the Gaia scanning law dictates this propagation and the ultimate sky distribution of the CTI-induced errors. The possibility of using the residuals of the astrometric solution to improve the calibration of the CTI effects is investigated. We also estimate the astrometric errors caused by (faint) disturbing stars preceding the stellar measurements on the CCDs. Finally, we show that, for single stars, the overall astrometric accuracy of Gaia can be preserved to within 10 per cent of the CTI-free case for all magnitudes by appropriate modelling at the image location estimation level and using the solution residuals.},
  author       = {Holl, Berry and Prod'homme, T. and Lindegren, Lennart and Brown, A. G. A.},
  issn         = {1365-2966},
  keyword      = {instrumentation: detectors,methods: analytical,methods: numerical,space vehicles,astrometry},
  language     = {eng},
  number       = {4},
  pages        = {2786--2807},
  publisher    = {Wiley-Blackwell},
  series       = {Monthly Notices of the Royal Astronomical Society},
  title        = {The impact of CCD radiation damage on Gaia astrometry - II. Effect of image location errors on the astrometric solution},
  url          = {http://dx.doi.org/10.1111/j.1365-2966.2012.20429.x},
  volume       = {422},
  year         = {2012},
}