There are a number of issues relating to the detector dark current that require investigation. We need to determine if the dark rate is linear in time at a given temperature. We need to determine if the dark rate is constant at a given temperature. We need to determine if the 2-D properties of the dark-current are significant and, if they are, if they are stable.
These considerations led to the following strategy: I obtained sets of Dark and Bias frames on four nights from 2004 January through 2004 June. On each of these nights, I obtained frames at a set of four temperatures, with temperature increments of 5 degrees C. For each temperature set, I obtained four dark frames with exposure times of 5, 10, 20 and 30 minutes. I also obtained a total of 13 bias frames at each temperature; five at the beginning of the set, five at the end, and one between each dark frame. On 16 January 2005 I obtained an additional sequence of Bias and Dark frames at T ~ -40 degrees C. The range of temperatures encompassed by this set of tests is
Future users are encouraged to obtain Dark sequences at T < -40 degrees C if the conditions present themselves.
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