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Image name: Open_Open_UV_Flood_1.png (click image to enlarge)
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Date submitted: 22-Apr-1997
RESULTS OF OPEN/OPEN UV FLOOD OF CCD
During the orbit '22-APR-97 08:17:21', '22-APR-97 09:45:19' a series
of 8 one-minute open/open exposures were taken. The purpose of this
experiment was to see if an open/open flood, which permits the entire solar
spectrum to reach the CCD through the leaks in the entrance filter, would
remove some of the radiation damage from the CCD.
First, it does not appear that this exposure had any adverse effects on the
device.
Second, the positive effect on the CCD was minor although probably real.
In the case of the diffuser signal, it seems that the change in total
signal of the 3 images is dominated by the orbital time from FMS rather
than by effects of the open/open flood. This is illustrated in the top
curve. However, the inset (a ratio of diffuser image 2 divided by image 0)
indicates some recovery, about 1 percent, of visible light signal in the
radiation damaged areas. The very worst damaged areas do not seem to have
been helped.
The lower curve indicates about a 2 percent decrease in the DPE=13 QR dark
signal of the SLD monitor image which may be related to the open/open
flood. It is possible that at least some of this change is orbital also.
Unfortunately, the pfi fixed-pointing images intended to look for changes
in "dark pixels" was not properly located on the CCD Either I got these
wrong or they were somehow changed in table processing. However, the pfis
which were observed showed no obvious changes from the open/open flood.
After further evaluation of this experiment and the darkcal that followed
it we may decide it is worth experimenting with a longer open/open flood.
Loren Acton
4/22/97
