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

98 CHAPTER 13. DATA CALIBRATION
• Polarization (AOT#5)
Again, like other PDSs the general PDS is created with get sscdstruct from an SSCD
containing sliced SPD SCDs. For example,
CIA> staring_pds = get_sscdstruct( staring_sscd )
where it is assumed that staring sscd is an IDL variable holding the name of the sliced SSCD.
In structure, it is the simplest of all PDSs (see Section 15.5.2 for more on the architecture
of the general PDS).
13.1.4 BS PDS
The BS PDS is designed to handle data from a beam-switch observation (AOT#3). Once you
have sliced your SPD SCDs you can convert them to a BS PDS in a similar manner to the other
PDS flavours. This time you use the routine get sscdbs. Note that there is one irregularity
which sometimes arises in beam-switch observations: some observers have programmed their
observations in reverse! Section 19.3 tells you how get sscdbs can be used to deal with this
problem.
Assuming that bs sscd is an IDL variable containing the name of your sliced SCDs’ SSCD
then you can create a BS PDS named bs pds with:
CIA> bs_pds = get_sscdbs( bs_sscd )
13.1.5 CVF PDS
The CVF PDS is designed to handle data from a CVF observation (AOT#4). In principle,
the CVF PDS is created like the raster PDS of Section 13.1.2, though with the CIA routine
get sscdcvf. The following example follows that of Section 12.2.3.
If the sliced SPD SCDs are not currently in memory they can be recovered from disk with
sscd read:
CIA> cvf_sscd = sscd_read( ’CSSC203056040001_96091918462427’, dir=scd_dir )
The next step is to create the CVF PDS from the SPD SCDs – the IDL string variable,
cvf sscd contains the name of their SSCD:
CIA> cvf_pds = get_sscdcvf( cvf_sscd, /del )
Note that the keyword del is set. CVF observations yield large quantities of data and it is
not wise to duplicate it in both an SSCD and a PDS – /del deletes the SSCD automatically
upon creation of the PDS.
As for a raster PDS you can look at the structure of a CVF PDSwithIDL’sHELP:
CIA> help, cvf_pds, /str
** Structure , 47 tags, length=9171368, refs=1:
CVF_NAME STRING ’LW-CVF2 8.78200 0.110000’
ASTR STRUCT -> ASTR_STRUC Array[1]
ENTWHL STRING ’HOLE’
SELWHL STRING ’LW large Mirror’
CVF_INCR INT 4