Because ASTERIX is designed as a multi-mission program it facilitates the inclusion of instrument dependent code for the PSF by the use of a PSF data routines library which it accesses using PSF system routines. (See Prog/011)
The PSF system controls access to the numerous PSF options which are presented to the user in the ASTERIX PSF user interface as follows;
PSF system options :
ANALYTIC ASCA EXOLE PWFC RADIAL
RESPFILE 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 /'XRT_PSPC'/ >
MASK - PSPC PSF option (LIST for descriptions) /'VARPROFILE'/ >
Loaded XRT PSF cube with 10 energy channels
AUX - Mean photon energy in KeV >
The reason for the large number of PSF options list above include: multiple missions and instruments, recalibrations, analytical options, searching for extended source, and techniques for improving the speed of PSF processing.