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