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.
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.