Last modified: 27 June 2019

URL: http://cxc.harvard.edu/ciao/why/hrc_ampsf.html

HRC AMP_SF Correction


There is a marginal instability in the HRC electronics that leads to a "ringing" in the amplifiers used in measuring event positions. Under certain conditions, the ringing is still present when the signals used to calculate the position are sampled, leading to a distortion in the calculated position for some events. Since the positions are calculated in ground processing (rather than on board the spacecraft), we apply a correction to minimize this distortion in normal HRC Level 1 processing. However, this correction requires a knowledge of the amplifiers' gain setting, or amplitude scale factor (AMP_SF), which differs from event to event. The AMP_SF is available in HRC telemetry, but it is often telemetered incorrectly. Fortunately, it is possible to deduce the correct value of AMP_SF from other HRC event data.

This correction became part of standard data processing at version DS 7.3.0. It is applied to the level=1 event file when running hrc_process_events.

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