ISOCAM Interactive Analysis User's Manual Version 5.0 - ISO - ESA

250 CHAPTER 20. ADVANCED DATA CALIBRATION
1. Save a copy of your PDS. Some calibration methods are irreversible (they change the data
in .CUBE and .MASK) and if you don’t like the result you will need to begin again with
fresh data.
2. Dark correction, deglitching and stabilization are all operations on .CUBE. These processes
must applied before any other and in the correct order:
(a) Dark correction.
Example: corr dark, pds, method=‘model’
Caveat: Irreversible. Dark correction can only be performed once. If you don’t like
the result of a dark correction, then you have to start again with the original
data.
(b) Deglitching.
Example: deglitch, pds, method=‘mm’
Caveat: Irreversible, but you could deglitch twice. However, there is a strong danger
of over deglitching your data. Best to begin again with the original data.
(c) Stabilization.
Example: stabilize, pds, method=‘s90’
Caveat: Irreversible, but you could stabilize twice with non-fitting methods such as
s90. However, it is not recommended.
3. Reduction of .CUBE to .IMAGE.
Example: reduce, pds
Caveat: Reversible. You can reduce as many times as you like. Although processes
following reduction will of course have to be repeated.
4. Flat-fielding.
Example: corr flat, pds, method=‘library’
Caveat: If the flat-fielding is performed on EXPOSUREs (as is the default) then the
flat-field correction can be reversed by re-reducing .CUBE to .IMAGE so as to create
‘fresh’ EXPOSUREs. If the flat-fielding was performed on IMAGEs (by setting the
corr flat keyword /cube) then the correction is irreversible.
5. Raster MOSAIC creation.
Example: raster scan, raster pds, method=‘noproj’
Caveat: Reversible. You can recreate the raster MOSAIC ad nauseum.
6. Beam-switch MOSAIC creation.
Example: reduce bs, bs pds
Caveat: Reversible. You can recreate the beam-switch MOSAIC ad nauseum.
After any of the above steps, the results can be evaluated before proceeding with the next
step. Routines to aid you are:
tviso to do general CAM image displaying (see Section 14.5.1);
x3d to look at the characteristics of the cubes .CUBE and .IMAGE (see Section 14.4.5);
xsnr to do S/N analysis of an IMAGE, EXPOSURE or MOSAIC (see Section 14.1.1).