ISIS, the Interactive Spectral Interpretation System, is designed to support the analysis and interpretation of high resolution X-ray spectra using a spectroscopy database such as the ATOMDB. It is currently a stand-alone, programmable and extensible S-Lang based system, independent of GUIDE and Sherpa, but is available from within Sherpa using import("isis");.

A variety of fitting modes are provided to support simple line profile fits as well as global fits; a pileup model for CCD spectra is also included (this is also available in Sherpa as the jdpileup model).

See the ISIS web page for more information and download instructions.