Identify and flag cosmic ray afterglows (L1)
acis_detect_afterglow infile outfile [logfile] [pha_rules]
[fltgrade_rules] [maxchain] [verbose] [clobber]
`acis_detect_afterglow' identifies residual charge from cosmic
rays in CCD pixels, released over consecutive exposures.
These events are flagged by status bits in the output event file.
The tool runs on a stack containing one or more event files and
produces a corresponding output file stack. The input stacks are processed
in a 1-1 pairing. The input file is read in one exposure at a time and
is checked against previously read exposures for afterglow events. When
a flaring pixel is detected, it is marked and a count of the total
number of exposures that the afterglow persisted is maintained. When
the afterglow subsides, reaches a user specified chain
length, or the end of the input file is reached, the number of
affected exposures is written in the corresponding output events.
To qualify as afterglow events, the event chip coordinates and
exposure numbers are always utilized; chip coordinates must be identical and the
exposure numbers must be consecutive. Optional criteria are the
checking of PHA, fltgrade and chainlength. These checks may be
done such that
the current row's values are less than, less than or equal to, or
equal to the previous row's values.
`acis_detect_afterglow' will run on any FITS event file
which contains the following columns: expno (long), chipx (short),
chipy (short), and status (32 bit). PHA (long) and fltgrade (short)
are only required if the "pha_rules" or fltgrade rules parameters are
set to anything other than "NONE". Other columns are not utilized but
merely propogated to the output file. It is the user's responsibility
to ensure that the columns specified above conform to the expected
data types. (Note: the types listed above are defined in the "ACIS
Level 1 to archive Interface Control Document" and are subject to
change.)
This tool was applied by the CXC pipeline to ALL ACIS observations
up until processing version DS 7.4.0. The use of
acis_detect_afterglow has been replaced by the use of
acis_run_hotpix. The "Remove the acis_detect_afterglow Correction" thread describes how to
remove the afterglow correction for cases in which the correction
may be inappropriate.
acis_detect_afterglow acisf051271721N001_evt1.fits
acisf051271721N001_ada_evt1.fits
Run acis_detect_afterglow on the file
acisf051271721N001_evt1.fits to create an output file
acisf051271721N001_ada_evt1.fits which has status bits
set for flaring pixels.
acis_detect_afterglow acisf051271721N001_evt1.fits
acisf051271721N001_ada_evt1.fits pha_rules=EQ fltgrade_rule=NONE
maxchain=16
Run acis_detect_afterglow on the file
acisf051271721N001_evt1.fits to create an output file
acisf051271721N001_ada_evt1.fits which has status bits
set for flaring pixel chains of length up to 16
exposures. Only count rows with identical pha values
(and chip positions). Do not check the fltgrade values.
Parameter=infile (file required filetype=input stacks=yes)
An event file or a stack of files.
This value specifies the name of the input event file(s)
to process. The specified files (FITS format) must exist
and have read permission. If using a stack, the number of
stack elements must have a 1-1 correspondence with the
outfile stack.
Parameter=outfile (file required filetype=output stacks=yes)
An event file or a stack of files
This value specifies the name of the output file(s) to create from the
input files. The files will be identical to the input files with the
exception of the status column which will have bits set to indicate
detected flaring pixels. If using a stack, the elements in the stack
must have a 1-1 correspondence with the items in the infile stack.
Parameter=logfile (file filetype=output default=stdout)
A text file or 'stdout'.
This value specifies the name of the ascii text file
which acis_detect_afterglow will generate if the verbose
parameter (see below) is set to a value other than 0. If
the value is set to "stdout", the output will be redirected
to standard output (typically the screen)
PHA criteria for subsequent events
The pha_rules parameter is used to specify the relationship
between the pha column of two consecutive exposures. The
check may be such that the current exposure's pha is less
than (LT), less than or equal to (LTEQ), equal to (EQ), or
not checked (NONE) against the previous exposure's pha value.
Fltgrade criteria for subsequent events
The fltgrade_rules parameter is used to specify the relationship
between the fltgrade column of two consecutive exposures. The
check may be such that the current exposure's fltgrade is less
than (LT), less than or equal to (LTEQ), equal to (EQ), or
not checked (NONE) against the previous exposure's fltgrade value.
Maximum number of exposures for a single flaring event
This value allows the user to specify the maximum number of exposures
that a flaring pixel should be counted for before resetting the count.
For values less than 16, it determines the maximum value of the after
glow status bits for chains that are of maxchain length.
Option which allows the user to request a varying level of
textual output to the log file based upon the program execution.
Levels range from 0 to 5 with 0 representing no information and 5
representing as detailed a log as possible.
Clobber output file if it exists?
Support for IRAF QPOE files has been removed from CIAO.
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