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I have an observation with frame repeats, and the repeated frames are full of weird (usually column-wise) structure. What can I do to fix these data?
Posted by Seppo Laine on 15 March 2010 05:08 PM
The first frame correction in the pipeline has not worked
well for such data. This was sometimes true for channel 3 data
in the cryogenic mission and this is currently always true for warm
IRAC data. The first-order mitigation is fairly simple. Take a median
average with outlier rejection of the difference images between
the first repeat and a given repeat, for example, median-average
the difference between the first and the second repeat frames (and
similarly, but separately, median-average the difference between the
first and the third repeat frames, etc.) Then add these median
difference images to your individual (C)BCD frames. For example, you
would add the median difference of the first and second repeat frames
to each second repeat frame.

An IDL code to perform this "delta-dark" correction is available
in the Spitzer Contributed software section at


http://ssc.spitzer.caltech.edu/dataanalysistools/tools/contributed/irac/repeatdeltadark/
.