WFPC2 Technical Instrument Report 98-02:
Analysis of the Excess Charge in WFPC2 Overscans
-Mutchler, O'Dea, and Biretta
We report an increase in the relative amount of excess charge in WFPC2 overscans over the instruments lifetime (1994 to 1998). We characterize the excess charge and discuss possible explanations for the increasing trend, including the possibility that it is deferred charge caused by a declining charge transfer efficieny (CTE) in the WFPC2 serial registers.