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

I.2. UPGRADING CIA 1.0 STRUCTURES 349
from CIA data structures is incorrect by a 180 degree rotation. Some programs are immune
to this error, saoimage and skyview for example, because they use the FITS CDELT and
CROTA2 keys to determine astrometry.
1. To update your CVF PDS first you need to know the roll of the spacecraft during
the observation in question. To do this look in the IIPH delivered with your CVF
observation data products and find the value of the key instroll. Youcandothisby
simple listing the contents of the IIPH file with VMS’s type or if you work in UNIX,
you can use more or the CIA routine readhdr:
CIA> print, readhdr(’iiph03800232.fits’,key=’instroll’)
./ iiph03800232.fits 229.970
2. Now run the routine struct update to fix the .ASTR.CD.
CIA> new_cvf = struct_update( old_cvf, roll=229.970 )
3. You may also want to correct FITS files you have created from CIA 1.0 CVF PDS.
To do this you will need to re-export your files – see Section 18.