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LIRIS Data Storage Modes
LIRIS data can be saved in three different ways using the storemode command.
The bias and dark level of near-IR detectors is usually not stable over time so a bias image (the so-called pre-read) is taken immediately before the actual exposure (the post-read). There is nothing one can do with the pre-read apart from subtracting it from the post-read, so the recommended setting for the store mode is diff:
SYS> storemode liris diff
Saves a FITS file with one extension. It contains the difference between the post-read and the pre-read, i.e. the "bias-subtracted" image only is stored. This is the recommended storemode.
SYS> storemode liris diff_pre
Saves a FITS file with two extensions. The first contains the difference between the post-read and the pre-read (i.e. what you would get using storemode diff), the second one the pre-read itself (i.e. a separate "bias").
SYS> storemode liris pre_post
Saves a FITS file with two extensions. The first contains the pre-read and the second the post-read.
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