Abstract
The European Space Agency's Gaia satellite was launched into orbit
around L2 in December 2013 with a payload containing 106 large-format
scientific CCDs. The primary goal of the mission is to repeatedly obtain
high-precision astrometric and photometric measurements of one thousand
million stars over the course of five years. The scientific value of the
down-linked data, and the operation of the onboard autonomous detection
chain, relies on the high performance of the detectors. As Gaia slowly
rotates and scans the sky, the CCDs are continuously operated in a mode
where the line clock rate and the satellite rotation spin-rate are in
synchronisation. Nominal mission operations began in July 2014 and the
first data release is being prepared for release at the end of Summer
2016. In this paper we present an overview of the focal plane, the
detector system, and strategies for on-orbit performance monitoring of
the system. This is followed by a presentation of the performance
results based on analysis of data acquired during a two-year window
beginning at payload switch-on. Results for parameters such as readout
noise and electronic offset behaviour are presented and we pay
particular attention to the effects of the L2 radiation environment on
the devices. The radiation-induced degradation in the charge transfer
efficiency (CTE) in the (parallel) scan direction is clearly diagnosed;
however, an extrapolation shows that charge transfer inefficiency (CTI)
effects at end of mission will be approximately an order of magnitude
less than predicted pre-flight. It is shown that the CTI in the serial
register (horizontal direction) is still dominated by the traps inherent
to the manufacturing process and that the radiation-induced degradation
so far is only a few per cent. Finally, we summarise some of the
detector effects discovered on-orbit which are still being investigated.
Original language | English |
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Journal | Astronomy & Astrophysics |
Volume | 595 |
Issue number | A6 |
Early online date | 24 Nov 2016 |
DOIs | |
Publication status | Published - 25 Nov 2016 |
Keywords / Materials (for Non-textual outputs)
- Astrophysics - Instrumentation and Methods for Astrophysics
- Astrophysics - Astrophysics of Galaxies
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Nigel Hambly
- School of Physics and Astronomy - Senior Researcher
Person: Academic: Research Active (Research Assistant)