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

204 CHAPTER 17. IMPORTING ISO DATA PRODUCTS TO CIA
Each ISOCAM image is stored in a vector (ISOCAM Handbook, Section 2.3.4). Before we
can reform and display them they need to be rescaled (ISOCAM Handbook, Chapter 7):
CIA> bscale = array.bscale
CIA> bzero = array.bzero
CIA> data = float(array.array)
CIA> for n = 0, 5 do data[ *, n ] = data[ *, n ]* bscale[n] + bzero[n]
The scaled data must now be reformed to the appropriate image size. To find the actual
image size in rows and columns we look at the fields .NAXIS1 and .NAXIS2 respectively.
CIA> naxis1 = array.naxis1
CIA> naxis2 = array.naxis2
CIA> print, naxis1, naxis2
80 80 80 79 79 79
80 80 80 80 80 80
To reform the images:
CIA> nb = naxis1 * naxis2 - 1
CIA> for n=0, 5, 3 do tviso, $
CIA> reform( data[ 0: nb[n], n ], naxis1[n], naxis2[n] )
When image sizes differ, only the first nb entries in each row of data are valid. Each sky
image stored in the CMOS is accompanied by a second equally sized image indicating the noise
level per pixel and a third image indicating the statistical weight assigned to each pixel. So in
the example above we only display every third image, i.e. the sky images.
17.2.2 Extracting a key from an ISO data product
With the procedure by extended fits key we can read selected keys directly from a FITS file
– this is more efficient then unnecessarily reading the entire file. The following extracts the data
from a CISP file and displays an image. 2
CIA> by_extended_fits_key, ’cisp14300601.fits’, data, ’cispdata’
CIA> help, data
DATA INT = Array(1024, 813)
CIA> tviso, reform( data[ *, 0], 32, 32 )
2 Refer to the ISO Data Product Document to find where the data is stored in the binary table, i.e. cispdata.