The Interactive Spectral Interpretation System (ISIS) was developed at MIT for the analysis of X-ray spectra.
You will make your ISIS-life A TON easier by setting up an ISIS history file that saves any interactive commands you use. They are usually automatically set on the Remeis-cluster, otherwise go to your .bashrc and use:
ISIS_HISTORY_FILE=/path_where_you_want_your_file_ususally_home/.isis_history export ISIS_HISTORY_FILE
Adapt for other shells accordingly.
A huge (and extremely useful) collection of useful ISIS functions, written and maintained by the Remeis observatory (and certainly containing thousands of working hours by a variety of people) can be found here:
Please cite properly when used!