Read Times and Dark Current Calibration in
ACCUM Mode
Because of the effects of shading, and the possibility that the underlying dark current may vary with time since reset, the removal of dark current (for calibration purposes, we implicitly assume shading and amplifier glow is a part of the time variable "dark current") from NICMOS data is more complicated than for many other instruments. The most accurate way to remove the dark current from any observation is a measurement of the dark current with an identical integration time and at the same detector temperature. For ACCUM observations we will make dark current calibration observations for a set of 8 exposure times for a single initial and final read below and 14 exposure times for 9 initial and final read. See Table 8.2 below.
Table 8.2: Exposure Times with Dark Current Calibration
Time (seconds) (NREAD=1) |
Time (seconds) (NREAD=9) |
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