Paper detail

Ageing of a space-based CCD: photometric performance development of the low Earth orbiting detectors of the CoRoT mission

In this thesis we have analysed the time evolution of the photometric precision achieved by the space-based exoplanet-hunting mission CoRoT during its flight phase (2007-2012). This study of the noise level of CoRoT light curves has been based on a previous paper by Aigrain et al. 2009, where they found a gradual degradation of the photometric performance over time for the first 14 months of data. Here we have analysed the anti-center runs IRa01 (2007), LRa01 (2008), LRa03 (2010) and LRa06 (2012). The two first runs were studied by Aigrain as well, so we are able to compare our results. The two last runs allowed us to evaluate the trend of photometric degradation over more than 5 years. We obtain low observational point-to-point noise, although a factor 3 bigger than the source photon noise. We find effects showing the ageing of the CoRoT CCDs. On 2h time scales we notice a receding photometric performance, with a noise increase of about 2.1 times across the four analysed runs, corresponding to a 15% increase per year. Correlated noise becomes more important than white uncorrelated noise for the two last studied runs, LRa03 and LRa06. The strongest degradation, however, occurs during the first year of operations, with a 30% noise increase, opening up a two-ageing-timescales scenario.