Instrument Science Report 2008-02:
Evolution of WFPC2 Superbiases
D. Thatte and J. Biretta
May 29, 2008
We examine the evolution of the WFPC2 superbiases from 1996 to 2007. Relatively little change is seen, implying generally good stability of the readout electronics during the 14+ years of WFPC2 mission. Most of the observed change results from the evolution of the dark current contained in the bias frames. The 2007 superbias also shows reduced row-to-row fluctuations in the WF4 CCD, which is a side-effect of the software used to remove the horizontal streaks associated with the WF4 anomaly.
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