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
@PeterKamphuis Could you make add the paper reference in the README a bit more accuratey (i.e. the arXiv reference?