With HXS_FSP you interactively choose data intervals, and fit the HXS spectrum,
using the routine fsp_11.pro. index and 
are the WBS index and data
structures. 
is the structure containing the results. Optional parameters are
- 
is a structure containing spectrometer
channel information, 
is a structure containing the data for each channel,
and 
are filenames for printouts and plots, respectively;
is a filename, if this option is set, the count rates are printed
into that file which may be fit by the routine FSP_PROC described above.
IDL> HXS_FSP, index, data, fit_pars
IDL> HXS_FSP, index, data, fit_pars, sc_par, ch_dta
IDL> HXS_FSP, index, data, outfile=outfile
IDL> HXS_FSP, index, data, pfile=pfile
IDL> HXS_FSP, index, data, countfile=countfile
IDL> HXS_FSP, index, data, fit_pars, sc_par, ch_dta, sdel=sdel