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

17.2. IMPORTING FITS TO REGULAR IDL DATA STRUCTURES 203
CIA> cds = calg2cds( ’ccglwdark.fits’, dir=product_dir, ack=ok )
CIA> help, cds, ok
CDS STRING = ’CCGLWDARK_96080515324098’
OK INT = 1
calg2cds returns the name of the formed CDS in memory. Nothing is written to disk by
this function. Use the CIA procedure cds write to save the CDS data structure to disk (see
Section 16.1.5).
17.2 Importing FITS to regular IDL data structures
This section describes CIA routines that can be used to read any extended FITS data products.
As such they can read the ISO data products into a regular IDL structure. The IDL ASTROLIB
also contains several FITS reading routines which are of interest: MRDFITS and READFITS.
CIA comes with a modified version of MRDFITS – the keyword option /savemem has been
added to save memory when reading large files.
17.2.1 Reading an ISO data product
The CIA routine ia extended fits read reads an extended FITS file into a conventional IDL
structure (not a PDS or SCD). For example, to read a CMOS data product (remember that
ISO data products are delivered in extended FITS file) we do the following:
CIA> ia_extended_fits_read, ’cmos14300601.fits’, header, array
CIA> help, hdr
HDR STRING = Array[209]
CIA> help, array
ARRAY STRUCT = -> Array[6]
The output arguments header and array contain the header of the FITS file and the data
from the FITS extensions. We can look at lines in the header by indexing header:
CIA> print, header[0]
SIMPLE = T / file does conform to FITS standard
To look at the binary table:
CIA> help, array, /str
** Structure , 38 tags, length=25896, refs=1:
CHANNEL STRING ’LW ’
INDEX LONG 1
TYPE STRING ’FLUX ’
BITPIX LONG 32
etc...