9.1 How to read to data

The files on the CD-ROM are ordered into subdirectories. For each observation there is a separate subdirectory on the CD-ROM (see the README file and the DATALIST file for more details). Many of the products are written in Binary FITS extension format (see chapter 8 for details on the file formats for LWS data). To read the data products observers can use several tools.

The IPAC first look tools

These are available from IPAC and allow the user to read in the FITS files, and create ASCII files from them. These tools are available for Sun/Solaris 2.4, Sun/SunOS 4.1.3, Dec/Ultrix 4.4, PC/Linux, Dec/Open VMS AXP V6.1. The tools can be downloaded from IPAC, see their worldwide web page:
http://www.ipac.caltech.edu/iso/iso.html

The ISO Spectral Analysis Package (ISAP)

This is an analysis package that was specifically written for LWS and SWS data. It can read in the product files and write a FITS file or an IDL save set. This package requires IDL. The ISAP package was not yet available at the time this manual was written. It will be made available via ftp by the ISO support centers in RAL (UK), IPAC (USA) and MPE Garching (Germany)

IDL with the astronomy library

Using IDL with the astronomy library, the observer can write his own code to read the data files, using the information in this IDUM (chapter 8). Below are some IDL commands that can be useful.

   To read the FITS primary header in variable hdr_prime:
   
   hdr_prime=headfits('<filename>')
   
   To read the binary header into variable hrd_bin:
   
   fxbopen,unit,'<filename>',1,hdr_bin
   
   To read the data from column N into variable X:
   
   fxbread,unit,X,N

A longer note on the use of IDL and the Astro Library to read LWS data can be found on the IPAC WWW pages (see above).