Journal
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Volume 430, Issue 4, Pages 3155-3170Publisher
OXFORD UNIV PRESS
DOI: 10.1093/mnras/stt121
Keywords
instrumentation: detectors; methods: laboratory; methods: numerical; space vehicles: instruments; astrometry; galaxies: general
Categories
Funding
- STFC Gaia Data Flow System grant
- European Marie-Curie research training network ELSA [MRTN-CT-2006-033481]
- ESA Research Fellowship
- UK Space Agency [ST/K00056X/1, ST/I000852/1, ST/K000756/1, PP/D006570/1] Funding Source: researchfish
Ask authors/readers for more resources
The European Space Agency (ESA) Gaia satellite has 106 CCD image sensors which will suffer from increased charge transfer inefficiency (CTI) as a result of radiation damage. To aid the mitigation at low signal levels, the CCD design includes supplementary buried channels (SBCs, otherwise known as 'notches') within each CCD column. We present the largest published sample of Gaia CCD SBC full well capacity (FWC) laboratory measurements and simulations based on 13 devices. We find that Gaia CCDs manufactured post-2004 have SBCs with FWCs in the upper half of each CCD that are systematically smaller by two orders of magnitude (<= 50 electrons) compared to those manufactured pre-2004 (thousands of electrons). Gaia's faint star (13 <= G <= 20 mag) astrometric performance predictions by Prod'homme et al. and Holl et al. use pre-2004 SBC FWCs as inputs to their simulations. However, all the CCDs already integrated on to the satellite for the 2013 launch are post-2004. SBC FWC measurements are not available for one of our five post-2004 CCDs but the fact that it meets Gaia's image location requirements suggests that it has SBC FWCs similar to pre-2004. It is too late to measure the SBC FWCs onboard the satellite and it is not possible to theoretically predict them. Gaia's faint star astrometric performance predictions depend on knowledge of the onboard SBC FWCs but as these are currently unavailable, it is not known how representative of the whole focal plane the current predictions are. Therefore, we suggest that Gaia's initial in-orbit calibrations should include measurement of the onboard SBC FWCs. We present a potential method to do this. Faint star astrometric performance predictions based on onboard SBC FWCs at the start of the mission would allow satellite operating conditions or CTI software mitigation to be further optimized to improve the scientific return of Gaia.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available