FAT is now surpassed by pyFAT (https://github.com/PeterKamphuis/pyFAT-astro) a much more flexible and hopefully more accurate version of the code. The IDL/GDL wrapper is merely retained for historical purposes. FAT is an IDL/GDL wrapper to automate TiRiFiC
GDL version is now ready for release and far superior to original. Proper Test documentation is included.