Notes on SMM GRS Response Matrix Files
Kim Tolbert, written 27-Mar-2019

grsmatrix.dat is the original SMM GRS response file that's been online in $SSW/smm/gen/dbase since 1997.

drm_mass_brd.txt and en_wid.txt contain matrix and photon bin center and edges for an improved matrix made by Gerry Share.

gerry_grs_drmnew.sav contains an improvement (by Richard Schwartz in March 2019) on drm_mass_brd matrix by forcing 
response to be centered on photont bins.  The save file contains the matrix, the input photon and the output count bins 
both in keV.  The save file was written by the routine grs_mod_share_mc_drm.