The psf system provides an instrument independent interface to psf
information for ASTERIX applications. A client application
associates a psf with a dataset (psf_associ), which can be
a binned dataset or an event dataset. The psf system identifies the
spatial axes within the dataset (using BDI and EDI), and the energy
axis if present. The psf system returns an ADI identifier to the application
which contains the psf state variables for that dataset. Subsequent
calls to the PSF system need only supply this identifier.
The psf system is in a fairly good state -- the only unfinished work
was to split up the psfrtn.f module to document the routines
properly and make debugging easier.