WF/PC INSTRUMENT SCIENCE REPORT 93-01:
The Evolution and Treatment of Hot Pixels in the WF/PC
by John Biretta, Christine E. Ritchie, and John MacKenty
February, 1993
Abstract excerpted from the report:
We examine the history of hot pixels in the WF/PC-1, and suggest improvements to the present dark calibration scheme. While new hot pixels continually appear (at ~30 per month per CCD), a substantial fraction (10 to 30%) are also lost during safings and decontaminations. For long exposures of faint targets, substantial improvement in dark calibrations can be obtained by using calibration data taken near the time of the science data. Calibrating with dark observations taken within one month of science observations reduces the number of residual hot pixels by a factor ~7 over the present pipeline reduction. Beginning in Spring 1993 dark calibration images will be taken at a rate of ~10 per month, which should give a large improvement (factor ~20) for future science observations where the dark calibration is an important limiting factor. Improvements related to "darktime" calculations and preflash calibration are also discussed.
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