summarize_status_bits

Synopsis

Summarize the status bits in a Chandra event file.

Syntax

summarise_status_bits filename

Description

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).

Examples

Example 1

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.

Example 2

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.

Example 3

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.

Example 4

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.

References

ACIS

ACIS status bits.

HRC

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.

Bugs

There are no known bugs for this tool.