Evolution of the integration time of the full CCD dark frames that are available for generating the desired dark signal model. The dark frame integration time pattern was not regular during the first year of the mission, until end of August 2011, since which time three dark frames are recorded each day with an integration time equal to 0.9, 7.4, and 16.4 s. Before June 2011, most days and many weeks exhibit no alternation of the dark frame integration time.