IRS Short-Low (Both) Mapping has non-0 bit-flags in PBCD tune.tbl
Posted by Tim Brooke on 25 July 2016 03:32 PM

This is a note about "tune.tbl" files for Spitzer IRS SL1+SL2 (Both)
5.2-14.5 micron spectral mapping, i.e. when the centering was between
the SL1 and SL2 active areas to record the spectra of both ranges
simultaneosly (rather than centering SL1 on a source, then SL2).  The
keyword for this mode is FOVNAME = 'IRS_Short-Lo_Module_Center'.  In
the Spitzer Heritage Archive Post-BCD tune.tbl files, points can be
"overmasked" in the bit-flags for this mode.  For example, many points
in SPITZER_S0_14587392_0346_8_E7446070_tune.tbl have bit-flag = 12416
= bits 7,12,13, which would normally be fatal.  If the data points
look otherwise normal, they are usually okay, except for bad end
wavelengths and any points with NaNs in flux or error.  The safe
wavelength ranges are 5.21-7.56 (SL2) and 7.57-14.28 (SL1).

For full confidence, it would be best to run the images through SPICE
to make your own final spectrum (bad pixels may be visible on the
images).  SPICE is available here:

And there are recipes to use SPICE here:

A general description of data reduction, including background subtraction,
is in the IRS Instrument Handbook, Chapter 8:

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