Calculate CC-mode Times of Arrival

Overview

Last Update: 18 Jun 2007 - expanded information in Check Source Coordinates section; included software version in which TIMEDEL keyword problem was corrected

Synopsis:

In continuous clocking mode event data files, the values recorded in the column TIME are the readout times instead of the times of arrival. (Note that the TIME values in timed exposure event data files are the times of arrival.) Before performing timing analyses, the times of arrival at the barycenter of the solar system should be computed. The first step of this process is to compute the times of arrival at the spacecraft from the readout times by removing the average time lag between the readout times and the times of arrival, the effect of the dither of the telescope, and the effect of motion of the detector relative to the telescope.

This correction became part of standard data processing (SDP) in DS 7.6.

Purpose:

To correct the event times in ACIS CC-mode observations for the time of arrival.

Read this thread if:

you are working with any ACIS CC-mode data observation, regardless of whether it is imaging or grating data processed with a software version lower than DS 7.6. The Get Started section shows how to find the software version used in SDP, and the Determine the eventdef parameter section shows how to find the mode of your observation.

Related Links:

• Why topic: Continuous Clocking Mode

• Apply Barycenter Correction thread: correct for the difference in photon arrival times as the Earth and Chandra move around the Sun. The barycenter correction should be done after running this thread.

Parameters for /home/username/cxcds_param/acis_process_events.par



#--------------------------------------------------------------------------
#
#  acis_process_events.par- Parameter file for acis_process_events program
#
#--------------------------------------------------------------------------
        infile = acisf00170_001N003_evt1.fits   Input event file or stack
       outfile = acis_170_new_evt1.fits Output event file name
    acaofffile = @pcad_asol1.lis  aspect offset file ( NONE | none | <filename>)
    (apply_cti = yes)             Apply CTI adjustment?
  (apply_tgain = yes)             Apply time-dependent gain adjustment?
(alignmentfile = )acaofffile -> @pcad_asol1.lis) sim/fam alignment file ( NONE | none | <filename>)
      (obsfile = NONE)            obs.par file for output file keywords ( NONE | none | <filename>)
      (geompar = geom)            Parameter file for Pixlib Geometry files
      (logfile = stdout)          debug log file ( STDOUT | stdout | <filename>)
    (gradefile = CALDB)           grade mapping file ( NONE | none | CALDB | <filename>)
     (gainfile = CALDB)           acis gain file ( NONE | none | CALDB | <filename>)
   (badpixfile = NONE)            acis bad pixel file ( NONE | none | <filename>)
   (threshfile = CALDB)           split threshold file ( NONE | none | CALDB | <filename>)
      (ctifile = CALDB)           acis CTI file ( NONE | none | CALDB | <filename>)
    (tgainfile = CALDB)           gain adjustment file ( NONE | none | CALDB | <filename>)
     (eventdef = {d:time,d:time_ro,s:ccd_id,s:node_id,i:expno,s:chip,s:tdet,f:det,f:sky,f:sky_1d,l:pha,
l:pha_ro,s:corn_pha,f:energy,l:pi,s:fltgrade,s:grade,x:status}) output format definition
   (doevtgrade = no)              Determine event flight grade?
 (check_vf_pha = no)              Check very faint pixels?
(calc_cc_times = yes)             Estimate the times of arrival for CC-mode observation?
        (trail = 0.027)           Trail fraction
     (spthresh = 13)              Default split threshold level (overridden by values in threshfile)
  (time_offset = 0)               Offset to add to event time field to synch w/ fam data
   (docentroid = no)              Determine pixel centroid for coord. conversion?
 (calculate_pi = no)              perform pha->pi conversion? (requires gain file)
 (pi_bin_width = 14.6)            Width of Pi bin in eV
  (pi_num_bins = 1024)            Number of values to bin energy into
 (max_cti_iter = 15)              Maximum iterations for the CTI adjustment of each event
 (cti_converge = 0.1)             The convergence criterion for each CTI-adjusted pixel in adu
       (tstart = TSTART)          header key containing start/default time value
        (tstop = TSTOP)           header key containing time of last event
      (clobber = no)              Overwrite output event file if it already exists?
      (verbose = 0)               level of debug detail (0=none, 5=most)
         (stop = sky)             end transformations at [chip,tdet,det,tan,sky,none]
     (instrume = acis)            axaf instrument- used for instrument parameter file
    (rand_seed = 1)               random seed (for pixlib), 0 = use time dependent seed
     (rand_pha = yes)             Randomize the pha value used in gain calculations
(rand_pix_size = 0.5)             pixel randomization width (-size..+size) 0=no randomization
      (stdlev1 = {d:time,s:ccd_id,s:node_id,i:expno,s:chip,s:tdet,f:det,f:sky,s:phas,l:pha,l:pha_ro,f:energy,l:pi,
s:fltgrade,s:grade,x:status}) TE faint modes event definition string
      (grdlev1 = {d:time,s:ccd_id,s:node_id,i:expno,s:chip,s:tdet,f:det,f:sky,l:pha,l:pha_ro,s:corn_pha,f:energy,l:pi,
s:fltgrade,s:grade,x:status}) TE graded event format definition string
       (cclev1 = {d:time,s:ccd_id,s:node_id,i:expno,s:chip,s:tdet,f:det,f:sky,f:sky_1d,s:phas,l:pha,l:pha_ro,
f:energy,l:pi,s:fltgrade,s:grade,x:status}) CC faint event format definition string
    (ccgrdlev1 = {d:time,s:ccd_id,s:node_id,i:expno,s:chip,s:tdet,f:det,f:sky,f:sky_1d,l:pha,l:pha_ro,s:corn_pha,
f:energy,l:pi,s:fltgrade,s:grade,x:status}) cc graded event format definition string
         (mode = ql)