Summarize the status bits in a Chandra event file.
The ACIS and HRC level 1 event files contain a STATUS column which is used to encode information about each event. The state encoded in each of the 32 bits is unique to each detector. Some of the bits encode hardware/telemetry problems (such as missing overclock values), some bits encode unexpected software processing results (e.g. CTI algorithm failed to converge), and some bits are informational (coincident with HRC anti-coincidence shield).
The summarize_status_bits tool examines the STATUS column in an event file and provides a summary of the reasons why the bits were set.
Unlike most CIAO tools, this script does not have a parameter file. It only accepts one argument: the name of the event file, which can include the DataModel virtual-file syntax (e.g. to apply a region filter or select a single chip).
unix% summarize_status_bits acis_evt1.fits
BitName Bit NumEvt %Evt BitDesc ------- --- ------ ---- ------- BADLM 1 43 0.0 Center pixel PHA not local maximum BADPIX 4 515728 13.6 Center of event island falls on bad pixel BADPIXE 5 258971 6.8 Surrounding event island falls on bad pixel BADBIAS 6 12386 0.3 Bad bias value (4095) GLOW 16 7373 0.2 Event is part of a cosmic ray afterglow CTIERR 20 764 0.0 CTI algorithm did not converge
This example shows the output running on an ACIS event file. All the events in the file are checked and the summary of the non-zero status bits is printed to the screen.
Note: since each event can have multiple status bits set, the sum of the NumEvt values may be larger than the number of events in the input file.
unix% summarize_status_bits "acis_evt1.fits[sky=region(ds9.reg)]"
BitName Bit NumEvt %Evt BitDesc ------- --- ------ ---- ------- BADPIX 4 286 1.5 Center of event island falls on bad pixel BADPIXE 5 738 3.9 Surrounding event island falls on bad pixel GLOW 16 38 0.2 Event is part of a cosmic ray afterglow
Similar to above, but only select the events in the specified region.
unix% summarize_status_bits hrc_evt1.fits
BitName Bit NumEvt %Evt BitDesc ------- --- ------ ---- ------- BADHYPU 0 81278 13.0 Hyperbolic test failed on U axis BADHYPV 1 71271 11.4 Hyperbolic test failed on V axis AMPSATU 2 49799 8.0 AMP saturation test failed on U axis AMPSATV 3 66035 10.6 AMP saturation test failed on V axis AMPFLATU 4 10842 1.7 AMP flatness test failed on U axis AMPFLATV 5 8563 1.4 AMP flatness test failed on V axis BADPI 7 2784 0.4 PI value out of range SIGAXIS 8 8633 1.4 Total signal on V or U axis is 0 SIGSUM 9 9584 1.5 Sum of signal on U and V axis are discrepant, position may be inaccurate SIGZERO 10 5000 0.8 Sum of all 6 tap is 0, event position is unknown BADRATIO 11 12069 1.9 PHA ratio test failed, likely a particle event BADCTRU 12 10605 1.7 U center tap is not local maximum BADCTRV 13 11362 1.8 V center tap is not local maximum SIGAXIS2 14 8633 1.4 Total on V or U axis is 0 (same as 8) BADPIX 15 39469 6.3 Event in bad region/pixel SIGLOW 16 2928 0.5 Signal below lower level discriminator, position may be wrong SIGHI 17 71671 11.5 Signal above upper level discriminator, may be particle TRIGU 20 74714 12.0 Number of U-axis taps with signal exceeding trigger above commanded level TRIGV 21 42240 6.8 Number of V-axis taps with signal exceeding trigger above commanded level RINGU 30 91078 14.6 U axis corrected for tap ringing effect RINGV 31 102176 16.4 V axis corrected for tap ringing effect
HRC event status bits encode many of the hrc_process_events test results. Events with some status bits set are still considered to be valid. Some of the bits are informational rather than being used as a selection criteria.
unix% summarize_status_bits acis_evt2.fits
All status bits are 0
ACIS level 2 event files have (by default), all status bits set to 0.
HRC status bits. Note: the enumeration of bits in this document is opposite from summarize_status_bits. So for example this memo describes BIT=1 as the V axis rining test. summarize_status_bits counts bits from right-to-left, starting at 0, so it will be reported as BIT=31.
There are no known bugs for this tool.