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

20.9. DEALING WITH DEAD PIXELS 251
20.8.1 PDS history
In general, operations performed on a PDS are recorded in .HISTORY. It lists routines and
calibration methods applied to the PDS:
CIA> print, staring_pds.history
date=26-May-1998 17:21:49 node=bikini user=mdelaney
procedure=darklibrary V 1.0 algorithm=Find best CCGLWDARK_97031713382678 END
date=26-May-1998 17:19:22 node=bikini user=mdelaney
procedure=spdtoscd V 2.0 algorithm=default
(7) cisp03001209.fits (7) $cia_vers/test
(2) 19 (2) 119 END
date=26-May-1998 17:21:54 node=bikini user=mdelaney
procedure=flat_library V 1.1 algorithm=Find best CCGLWOFLT_98041510080669 END
date=26-May-1998 17:21:55 node=bikini user=mdelaney
procedure=flat_library V 1.1 algorithm=Find best CCGLWDFLT_98031519384439 END
date=26-May-1998 17:21:40 node=bikini user=mdelaney
procedure=get_sscdstruct V 2.1 algorithm=default
CSSC030012090001_98052617205667 END
date=13-Jul-1998 10:53:06 node=bikini user=mdelaney
procedure=corr_dark V 3.9 algorithm=cube = (cube/gain/tint)-dark model END
etc...
If you use CIA routines to convert your PDS to a FITS file, the text in .HISTORY is saved
in the FITS header (see Chapter 18).
20.9 Dealing with dead pixels
Usually, the only dead pixels you need worry about are the four of the SW detector and column
24 of the LW detector. However, if you have very heavily glitched or unstable data, then
after calibration a pixel may be masked all the way through a set of IMAGEs from a STATE.
When reduced to an EXPOSURE, such pixels will be effectively dead in that EXPOSURE.
Their corresponding value in .NPIX will be zero, in other words they will have a zero weight.
raster scan ignores all dead pixels – if EXPOSUREs do not overlap where a dead pixel occurs,
then a blank spot will appear in the MOSAIC.
Note the following when you are dealing with data from the LW detector: after calibration,
but before building the raster MOSAIC, calib struct automatically smooths column 24 in the
.IMAGE and .CUBE. However, the weight of every pixel, i.e. the values in .NPIX, in column 24
will always remain as zero. Therefore column 24 will appear as a dead column in the MOSAIC.
However, it will no longer be column 24, but column (.NX RASTER-8).
Dead pixels appearing in the raster MOSAIC are optionally smoothed by calib raster:
1. /dead
method: Where dead pixels appear in the raster MOSAIC, i.e. where .NPIXRASTER
is zero, a median smoothing method is applied. Only the dead pixels are smoothed
into their neighbors – no other pixels are affected.
called routine: im smooth
PDS side effects: Dead pixels in .RASTER are smoothed.