Instrument Science Report 2008-02:

Evolution of WFPC2 Superbiases

D. Thatte and J. Biretta

May 29, 2008

Abstract:

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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