PROFFAST is a software package for retrieving trace gas concentrations from interferograms measured with Bruker EM27/SUN solar absorption FTIR spectrometer by using Bruker OPUS software. The PROFFAST software package is developed at the Karlsruhe Institute of Technology (KIT) and funded by the European Space Agency (ESA). Recently, PROFFASTpylot was created to run PROFFAST under Python.