A general discussion of the McTiernan spectral fitting programs is given
on page 
in the description of fitting WBS spectra.
Also available are spectrometer-type fits for SXT data. In order to do
this, the regular SXT filter response functions are rewritten as if
they are spectrometer channel response curves. SXT_FSP calls
SXT_PREP and SXT_INTERP to get the data in the appropriate form.
Then the routine ANY_FSP is called, which does the spectral fit in
the same manner as the HXS or HXT. Only two types of fits can be used
for SXT_FSP, the thermal SXR lines fit (tyspec 
) or the single
power law fit (tyspec 
). Thus it is possible to get single
temperature fits using three or more filters. SXTBOX_FSP does the
same thing, except for regions chosen by the user, as in HXTBOX_FSP.