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Last modified: 26 October 2016

URL: http://cxc.harvard.edu/ciao/bugs/acis_process_events.html

Bugs: acis_process_events


Table of Contents

Caveats


Caveats

Status bits in the input file are not reset when reprocessing data

When acis_process_events is used to reprocess event data, it does not unset status bits in the input data file. For example, acis_process_events does not recalculate the bad pixel status bits. If events have status bits set in the input event file, then the values are always copied to the same bits in the column STATUS of the output file. If the badpixfile is set to a value other than "NONE" (the default), then only additional status bits can be set in the output file. This limitation will be fixed in a future release.

The exception to this is the VFAINT background cleaning (status bit 23). As of CIAO 4.0, previously set VFAINT status bits are unset before the check is done again.

# acis_process_events (CIAO): WARNING: problem reading ctifile,
  cti adjustment will not be applied. Changing apply_cti=yes to apply_cti=no.

The most common cause for seeing this warning is that the observation does not contain -120C data. Since the CTI correction is primarily calibrated for this focal place temperature, it is not possible to use it on other observations. Note that this is not an error; if no CTI file is found, acis_process_events continues running as if apply_cti=no and produces a valid output file that has not been CTI-corrected.

The CTI Correction why topic has more information on the correction.

# acis_process_events (CIAO): The following error occurred 31 times: 
  dsAPEPULSEHEIGHTERR -- WARNING: pulse height is less than split
  threshold when performing serial CTI adjustment.

When the CTI adjustment is applied to events on the back-illuminated CCDs (ACIS-S1 and S3), sometimes one of the pulse heights in a 3x3 pixel event island can drop below the split threshold if it was above the threshold before the adjustment. In the end, pixels that are below the split threshold are ignored when the total pulse height and energy are computed.

If the number of times is small, then the warning may be safely ignored.


Last modified: 26 October 2016
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