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Hubble Space Telescope
NICMOS Safing Recovery Advisory

The NICMOS Team made several tests of the instrument on February 2-3, 2007 and confirmed that NICMOS is back to its nominal operational status. In particular, the functionality of the filter wheels was tested and verified through a set of flat exposures. The flats also provided a comparison of the count-rates, which were found to be the same as for pre-safing flats. A direct comparison of the biases before and after the recent safing shows that there is no significant change in any of the three cameras. The dark current was characterized by comparing the post-safing data for each camera with results from the regular calibration program. The ratios are all found to be within the statistical error.

Darks:

This is a comparison between the nicmos darks taken before and after the safing. The results are based on the first darks data set only.

To investigate if there is a systematic difference between the 'new' and the 'old' darks, we create images of the ratio between pre and post safing data. We thereafter use the mean of these ratio images to measure the deviation from unity.

As Table 1 shows, there is no systematic difference when comparing the new and the old darks and the deviation from unity is within statistical errors. A similar scatter is seem when comparing new and old darks separately.

This comparison is based on the first post-saving data only, when additional data becomes available during the coming days, more detailed tests will be made.

Table 1: Mean of Ratio Between Dark Images
NEW-NEW NEW-OLD OLD-OLD
NIC 1 0.93 0.08 1.04 0.08 1.00 0.08
NIC 2 1.07 0.09 0.96 0.09 1.08 0.10
NIC 3 0.92 0.09 1.08 0.09 0.96 0.08