On May 27, 2003 CAP 843 was used to cool the ACA CCD from -11C to -12C. This cooling is the second step in a ten week process of reducing the temperature from -10C to -15C. Feasibility analysis was done by RAC and is posted in a 17-Feb-2003 report. This report details the intermediate results.
Monitor windows selected to track specific regions of the CCD have been scheduled into perigee pass observations since the APR2803 week. Below are pre-cool and post-cool histograms of warm pixels (>100 e-/s) in an 8x8 region of the CCD centered on y-angle=2306, z-angle=-1290 (row = -254.5, col = -494.5).
Also of interest are the pre- and post-cool temperatures of the ACA and the CCD, as well as the TEC set point. The plots below are constructed from monitor window data during the weeks immediately before and during the cooling process. No unexpected changes are evident.
No large scale effect on the spacecraft bus current was expected, as the increase in power consumption is very low (a few Watts). This has been checked and verified. The bus current is essentially unchanged.
The next step in the cooling process (from -12C to -13C) is expected to proceed on Thursday, Jun 11th.
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Email: Brett Unks |