Hello new recruit! The new version of SAMSIM which is much easier to use is available at: https://gitlab.rrz.uni-hamburg.de/bay7770/samsim3.0/-/tree/master
To get started read the comments of SAMSIM.f90, or look directly into documentation/Reference_manual.pdf, which was generated from the source code via doxygen. For questions contact Philipp Griewank (philipp.griewank@univie.ac.at), Niels Fuchs (niels.fuchs@uni-hamburg.de), or Dirk Notz (dirk.notz@uni-hamburg.de). Good luck!
If you are intersted in brightness temperatures, we highly recommend you look at the following project, which contains the code Clara Burgard created: https://github.com/ClimateClara/scripts_paper_arc3o_part1. The repository also contains the version of SAMSIM she used, along with various additional exripts which could be of interest.