niprescreen - perform prescreening of NICER data


niprescreen infile outfile


The niprescreen task performs basic preliminary screening of NICER event files. Overall this task is meant to be used internally by other NICER tasks and generally not by the end-user.

The use of niprescreen is to both do basic early screening of data which can remove large amounts of useless events, and also to pre-allocate some columns, which speeds up following calibration and calculation steps.

The user specifies the required screening criteria using the expression parameter, which can use any standard rowfilter filtering expressions.

niprescreen also applies flagging for "noise ringer" events, which are events that are detected within a certain time since the previous undershoot in the same detector. The time range is specified by the undertime parameter. These events are typically electronic ringing noise. Those events within the set time have the NICER_FLAG_RING bit set.

If stdcalcols=YES, then standard calibration columns are created in the output FITS file. This can save execution time by downstream software, which may take a more piecemail approach to adding columns.


infile [filename]
Name of input "UF" NICER event file to be processed.
outfile [filename]
Name of output screened NICER event file.
(expression = "(T)") [string]
An optional expression used for event filtering. Any standard rowfilter expression can be used, or "(T)" to indicate all events should be accepted.
(undertime=110.0) [real]
Time interval to use for noise ringer flagging, in units of microseconds. A value of 0 disables this flagging.
(delta=NO) [boolean]
If YES, then then create a column in the output file named DELTA, which will have the time in seconds since the previous undershoot.
(stdcalcols) [boolean]
If YES, then pre-allocate blank columns to be used by NICER standard calibration tools.
(clobber = NO) [boolean]
If the output file already exists, then setting "clobber = yes" will cause it to be overwritten.

(chatter = 2) [integer, 0 - 5]
Amount of verbosity of the task. For chatter=0, no output is printed. For chatter=5, debugging output is printed.

(history = YES) [boolean]
If history = YES, then a set of HISTORY keywords will be written to the header of the specified HDU in the output file to record the value of all the task parameters that were used to produce the output file.


1. Apply NICER calibration to data from observation 1706221428.

  niprescreen indir=1706221428 outdir='$INDIR/xti/event_cl' clobber=YES 

The input directory is a NICER observation number 1706221428. The output files are placed in the observation directory under 1706221428/xti/event_cl/ni1706221428_0mpu*_ufa.evt. Note that single quotes are used to prevent $INDIR from being expanded by the Unix shell. The default calibrations files are taken from CALDB.





Apr 2018