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

26 CHAPTER 3. RASTER OBSERVATION (CAM01)
CIA> help, raster_pds, /str
** Structure , 54 tags, length=1399800, refs=1:
RASTERCOL INT 4
RASTERLINE INT 2
M_STEPCOL FLOAT 84.0000
N_STEPLINE FLOAT 84.0000
RA_RASTER DOUBLE 180.47414
DEC_RASTER DOUBLE -18.878420
ANGLE_RASTER DOUBLE 109.43000
RASTER_ROTATION DOUBLE 199.43000
RASTER_ORIENTATION
STRING = ’SPACECRAFT Y_AXIS’
ASTR STRUCT -> ASTR_STRUC Array[1]
NX_RASTER INT 116
NY_RASTER INT 60
RASTER FLOAT Array[116, 60]
etc...
5. Now it is time to do some actual calibration. However, before we proceed let’s take a
look at some of the effects we want to eliminate from our data. At the moment the most
substantial portion of our data is held in a raster pds.cube. This is a cube of raw CAM
IMAGEs taken from all the SCDs of the first clean SSCD. We will use x3d to take a look
at this cube of IMAGEs – see Figure 3.1.
CIA> x3d, raster_pds
Cube(1,9,106) = 134.000
x3d is a tool for browsing through the frames of a cube – in our case the frames are CAM
IMAGEs. One IMAGE is displayed at a time. The slider bar to the right of the displayed
IMAGE can be used to flick through the cube. A plot above the IMAGE displays the value
of a selected pixel (selection can be done by right-clicking on the IMAGE) throughout the
cube. In effect, this is the history of that pixel during the entire CONFIGURATION.
Upon calling, x3d displays the center frame of the cube, i.e. raster pds.cube[ *, *, 106].
The are several effects evident in this IMAGE. Dark current causes the alternately dark
and bright horizontal lines. The bright pixels at the bottom left of the IMAGE is a cosmic
ray glitch – this is clear from the sharp spike in the history of the currently selected pixel,
raster pds.cube[1, 9, 106]. Additional effects which are not obvious in Figure 3.1 are: (i)
pixel to pixel non-unformity which need to be corrected by flat-fielding, (ii) instability in
the detector which can be corrected by a variety of fitting and masking routines. We will
now attempt to remove all these effects.
There is a set of CIA calibration routines that we will use to do all the necessary data
calibration and correction – Chapter 20 contains more detail on these routines. Almost
all of these routines accept any flavour of PDS, the one exception is the raster MOSAIC
creation routine. This is of course specific to a raster PDS. All these routines have a choice
of different methods, though for simplicity we will just use the default here. Now we will
perform the following corrections: (i) dark correction, (ii) deglitching, (iii) stabilization.