What is the status of the response matrix for the PSPC?
Data taken prior to Oct 14th 1991 should be fit with the matrix pspcb_92mar11.rmf (or pspcc_92mar11.rmf for data taken during the survey or PVC phase when pspcc was operational). Data taken after that date should be fit with pspcb_93jan12.rmf. These matrices are in GSFC OGIP FITS format and compatible with XSPEC. These FITS matrices can be used with FITS or SF format XSPEC pha files and they are available on the legacy anonymous ftp area under /caldb/data/rosat/pspc/cpf/ (where cpf stands for calibration product file).
Uncalibrated gain shifts may produce an S-shaped discrepancy in the data minus fitted model residuals, the matrices currently are undergoing recalibration to correct for these problems. New matrices will be advertised when available. Also see question #3.
Please use the Feedback link if you have questions on ROSAT.