nicertimecal - apply clock calibration to NICER event file


nicertimecal infile hkfile calfile [outfile]


This task applies clock calibration to NICER event files timestamps. It adjusts the measured time values for known instrumental biases.

The end result a revised 'TIME' column in the output event file. Note that the old time values are effectively overwritten, so the user is strongly advised to not use this task on the original NICER "_uf" event files. Normally this task will be run as a part of the 'nimpucal' task.

Also note that it is not possible to apply clock calibration more than once to an event file. Once the TIME column is overwritten it cannot be recalibrated. After calibration, the CLOCKAPP keyword is set to 'T' to reflect this status.

This task currently corrects for the known electronics delays within the instrument, as well as a global 1 second timestamp offset introduced within the flight master computer.


infile [filename]
Input file name. Name of a NICER event file to have clock calibration performed upon it. If outfile=INFILE then the input file will be modified in place, otherwise it will be untouched.
hkfile [filename]
Name of MPU housekeeping file, available in each observation.
calfile [filename]
Name of FPM/MPU clock calibration data file, or "CALDB". For standard operation, the NICER team recommends to use "CALDB".
outfile [filename]
Name of output event file, or "INFILE". A new file named outfile will be created with modified TIME column. If outfile=INFILE, then the input file will be modified in place without creating a new file.
(leapinit="AUTO") [string]
Initialize LEAPINIT keyword of event extensions? An integer value indicates to use that many leap seconds. A value of "AUTO" indicates use the appropriate number of leap seconds for the given observation TSTART. A value of "NONE" indicates to not change LEAPINIT.
(calstation="FLIGHT") [string]
Station where data was collected. For in-flight operations use calstation=FLIGHT. For ground-based testing, other values can be used. This parameter selects the NICSTATN keyword value in CALDB.
(cleanup="YES") [boolean]
If yes, then clean up temporary files. If no, temporary files remain. This is typically for debugging.
(timeoffset=0.0) [real]
Constant time offset to add to housekeeping timestamps to bring them into alignment with event timestamps.
(clobber = NO) [boolean]
If the output file already exists, then setting "clobber = yes" will cause it to be overwritten.
(chatter = 1) [integer, 0 - 5]
Controls the amount of informative text written to standard output. Setting chatter = 4 or higher will produce detailed diagnostic output; chatter = 1 prints out a basic diagnostic message. The default is to produce a brief summary on output.
(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 nicertimecal task parameters that were used to produce the output file.


This is a typical invocation:

nicertimecal crab_pulsar.evt mpu_hk.fits CALDB outfile=INFILE
The event file to be calibrated is crab_pulsar.evt. Since outfile=INFILE, the input file is modified in place. The task queries CALDB for the gain calibration file.


Jul 2018