Go to HETG at XRCF
By combining the HETG Efficiency files with Calibration Interface Products from the HRMA, ACIS and HRC, tables of effective area for the various instrument configurations were created and are available as HETGS CIPs. These are the effective areas combining left and right orders and including all photons in the cross-dispersion direction.
The location in energy of the chip-gaps is seen in these files and can be independantly calculated with the stand-alone IDL procedure hetgs_gaps.pro.
These files were created by the (dph and dd written) IDL procedure main_hetg_m.pro (and main_letg_m.pro for LETGS) in the directory ~dd/idl/Aeff_calc/ at MIT. General Chandra parameters are assigned system variables by the include file AXAF_params.pro (this files has the 0.9 factor to go from "MST area" to "flight prediction area"). The input files are the grating shell-averaged efficiency files, hrma.rdb, acis_qe.rdb, and acis_fil.rdb. In addition, the ACIS-S and ACIS-I geometry are "stored" in the procedures aciss_geometry.pro and acisi_geometry.pro. Tables were output with the procedure output_tables.pro. Work-horse sub-procedures are rdb_read.pro, rdb_write.pro interpol_sort.pro.
The HETG would preferably be used with the HRC-I because of the width of the HETG "X" pattern, the narrowness of the HRC-S, and the complexity of the HRC-S filters. The HRC-I and ACIS-S variously are backups for the LETG-HRC-S. Creation of these effective areas is straight forward from the CIP files, see hetgs_hrc_i.pro.
The LETG is nominally combined with the HRC-S. Calculation of the LETGS 1st order efficiency is complicated by i) the filter structure ii) the segment gaps, and iii) variations in the HRC-S segment's QE with position. Ralph Kraft of HRC has made a first analysis of this effective area (excluding the grating efficiency), see http://hea-www.harvard.edu/HRC/calib/hrcs_qe.html.
This RK HRC-S data was combined with the LETG efficiency to produce the baseline LETGS first-order effective area EA_LETG1-HS.rdb. A good approximation to this curve is given by no_spatial_EA_LETG1-HS.rdb which includes all but the spatial variation effects (created by letgs_rk_compare.pro). The plot below shows the RK HRC-S efficiency combined with the LETG efficiency (solid line); the no-spatial-variations calculation is shown dashed.
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