The psf system is used by Asterix commands which have to access PSF information in an instrument independent manner. Generally the user will have a dataset produced by an instrument interface, such as the EXOSAT or XRT interface, and this will direct the psf system to the appropriate information.
The psf system displays a menu of options available, controllable using the PSF prompt. For example,
The menu is in two parts - the first lists those psfs which can be invoked by name (ANAL to XRT_PSPC) - the second shows allowed psf model specifications. The latter are used with applications which psf require a spatially varying psf, or one with energy dependency.ICL > PSS IMAGE ... PSF system options : ANAL ASCA EXOLE RESPFILE PWFC TABULAR WFC XRT_HRI XRT_PSPC CSPEC(psf/model,spec[,nbin]) POLAR(psf,rbin[,abin]) RECT(psf,xbin[,ybin]) PSF - Choose PSF to use for source model /'ANAL'/ > xrt_pspc