XMM-Newton Data Files Handbook

3.6 Compression

With few exceptions, all PPS products are supplied in compressed form, that is, each product is individually compressed using the Unix command gzip. The exceptions are:

• PNG product files. PNG is already an intrinsically compressed format.
• PDF product files. These are created intrinsically compressed.
• PPS run message product files, that are (small) ASCII files.
• HTML files. Browsers do not understand gzipped HTML files.

Note that fits file viewers like fv or ds9, as well as the SAS tasks can work on compressed FITS files, and it is therefore not necessary to uncompress. However, for very large files, the SAS tasks run significantly faster if the files are uncompressed beforehand.