The ASCA and EXOLE options refer to other satellite missions, while the WFC, XRT_HRI and XRT_PSPC are different ROSAT instruments which each require their own PSF.
PWFC* - The WFC in pointed mode WFC - The WFC in survey mode XRT_HRI - The ROSAT XRT, HRI detector XRT_PSPC*! - The ROSAT XRT, PSPC 1 and 2 detectors * These psf routines vary with position across the field of view ! These psf routines support energy modelling using the CSPEC model