Last modified: 24 September 2021

URL: https://cxc.cfa.harvard.edu/ciao/why/hrc_tgain.html

HRC-S Time-dependent Gain Corrections and PI Filter


A new HRC-S gain map and pulse-height filter was introduced in CALDB 4.9.6 (21 September 2021) fixing issues found in the prior gain map version introduced in CALDB 4.9.2 (6 July 2020). The original intent was to remove over half of Level=2 background events at wavelenghts >20 Å with a loss of ~1% of X-ray events; however, it was found that the HRC-S/LETG background filter sometimes removed an excessive aamount of valid X-ray events, primarily at negative orders, with observations beginning ~2017 and increasing over time, with losses up to 6% at some wavelengths by the end of 2020. The new gain maps and pulse-height filter has been now corrected, as described in the "HRC-S Adjustment for Very Low Gain" memo.

The primary differences from the old gain map and PI filter are:

Relevant Plots

Users working with HRC-S data should reprocess to improve the TGAIN calibration in their data by running the chandra_repro script or by following the Create a New Level=2 Event File thread. The PI background filter is applied to HRC-S/LETG data, as explained in the "Apply background filter" section of the LETG/HRC-S Grating Spectra thread.