HRC AMP_SF Correction and Reducing Tap-Ringing Distortions

Overview

Last Update: 8 Feb 2008 - added deprecated thread message to Synopsis

Synopsis:

This thread has been deprecated and will be removed in the next CIAO release. Instead of running this thread, follow the Reprocessing Data to Create a New Level=2 Event File thread.

There is a marginal instability in the HRC electronics that leads to a "ringing" in the amplifiers used in measuring event positions. Under certain conditions, the ringing is still present when the signals used to calculate the position are sampled, leading to a distortion in the calculated position for some events. Since the positions are calculated in ground processing (rather than on board the spacecraft), we apply a correction to minimize this distortion in normal HRC Level 1 processing. However, this correction requires a knowledge of the amplifiers' gain setting, or amplitude scale factor (AMP_SF), which differs from event to event. The AMP_SF is available in HRC telemetry, but it is often telemetered incorrectly. Fortunately, it is possible to deduce the correct value of AMP_SF from other HRC event data.

This correction became part of standard data processing at software version DS 7.3.0.

Purpose:

To correct the AMP_SF values in HRC level=1 event files and to use these new values to reduce the tap-ringing distortion in the HRC event position reconstruction. A new level=2 event file is then generated.

Read this thread if:

you are working with any HRC-S or HRC-I observation, regardless of whether it is imaging or grating data, that was processed with a software version lower than DS 7.3.0; the Determine the RANGELEV keyword section shows how to check the version of the software used in processing your data.

Calibration Updates:

• CALDB v3.4.1 (14 Sep 2007): A new gap lookup table, hrciD1999-07-22gaplookupN0003.fits, is needed to improve the off-aimpoint gap map solution for HRC-I at certain locations. The CALDB 3.4.1 section of the CIAO release notes has more information.

Related Links:

• Analysis Guide: HRC Data Preparation
• Improving Chandra High Resolution Camera event positions via corrections to crossed-grid charge detector signals (also available in PS format, 11 pages)
• An Improved AMP_SF Correction Scheme

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


#
#  Parameters for the hrc_process_events task
#
        infile = hrcf01557_000N002_evt1.fits    input level 0 event file/stack
       outfile = hrc_1557_new_evt1.fits output level 1 file
    badpixfile = hrcf01557_000N001_bpix1.fits bad pixel file ( NONE | none | <filename>)
    acaofffile = pcadf100494341N001_asol1.fits aspect offset file ( NONE | none | <filename>)
      (geompar = geom)            Parameter file for Pixlib Geometry files
(alignmentfile = )acaofffile -> pcadf100494341N001_asol1.fits) sim/fam alignment file ( NONE | none | <filename>)
      (obsfile = NONE)            obs.par file for output file keywords ( NONE | none | <filename>)
     (gainfile = CALDB)           gain correction image file ( NONE | none | <filename>)
      (ADCfile = NONE)            ADC correction table file ( NONE | none | <filename>)
    (degapfile = CALDB)           degap factors (NONE | none | COEFF | <filename>)
      (hypfile = CALDB)           Hyperbolic test coefficients file ( NONE | none | <filename>)
 (ampsfcorfile = CALDB)           caldb file for amp_sf_correction( NONE | none | <filename>)
      (tapfile = CALDB)           tap ring test coefficients file ( NONE | none | <filename>)
   (ampsatfile = CALDB)           ADC saturation test file ( NONE | none | <filename>)
  (evtflatfile = CALDB)           Event flatness test file ( NONE | none | <filename>)
      (badfile = NONE)            output level 1 bad event file
      (logfile = stdout)          debug log file (STDOUT | stdout | <filename>)
     (eventdef = )stdlev1 -> {d:time,s:crsv,s:crsu,s:amp_sf,s:av1,s:av2,s:av3,s:au1,s:au2,s:au3,
l:raw,s:chip,l:tdet,f:det,f:sky,s:pha,s:pi,s:sumamps,s:chip_id,x:status}) output format definition
  (badeventdef = )badlev1 -> {d:time,s:crsu,s:crsv,s:au1,s:au2,s:au3,s:av1,s:av2,s:av3,s:pha}) output format definition
   (grid_ratio = 0.5)             charge ratio
    (pha_ratio = 0.5)             pha ratio
  (wire_charge = 0)               turn on center wire test (-1=off,0=on)
         (cfu1 = 1.0)             u axis 1st order cor. factor
         (cfu2 = 0)               u axis 2nd order cor. factor
         (cfv1 = 1.0)             v axis 1st order cor. factor
         (cfv2 = 0)               v axis 2nd order cor. factor
  (time_offset = 0)               Offset to add to event time field to synch w/ fam data
     (amp_gain = 75.0)            amp gain
     (instrume = hrc-s)           hrc instrument- used for parameter file
(do_amp_sf_cor = yes)             perform amp_sf correction (y/n) ?
     (do_ratio = yes)             perform ratio validity checks
       (tstart = TSTART)          header key containing default time value (HSI)
        (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)
    (rand_seed = 1)               random seed (for pixlib), 0 = use time dependent seed
(rand_pix_size = 0.0)             pixel randomization width (-size..+size), 0.0 = no randomization
        (start = coarse)          start transformations at [coarse,chip,tdet]
         (stop = sky)             end transformations at [none,chip,tdet,det,sky]
      (badlev1 = {d:time,s:crsu,s:crsv,s:au1,s:au2,s:au3,s:av1,s:av2,s:av3,s:pha}) event format definition string
      (hsilev1 = {d:time,s:crsu,s:crsv,s:au1,s:au2,s:au3,s:av1,s:av2,s:av3,s:chipx,s:chipy,s:tdetx,s:tdety,
s:x,s:y,l:fpz,s:pha,s:vstat,s:estat}) event format definition string
      (stdlev1 = {d:time,s:crsv,s:crsu,s:amp_sf,s:av1,s:av2,s:av3,s:au1,s:au2,s:au3,l:raw,s:chip,l:tdet,
f:det,f:sky,s:pha,s:pi,s:sumamps,s:chip_id,x:status}) event format definition string
      (simlev1 = {l:tick,i:scifr,i:mjf,s:mnf,s:evtctr,s:crsu,s:crsv,s:au1,s:au2,s:au3,s:av1,s:av2,s:av3,
s:tdetx,s:tdety,s:pha,s:vstat,s:estat}) sim event definition string
      (fltlev1 = {d:time,s:crsv,s:crsu,s:amp_sf,s:av1,s:av2,s:av3,s:au1,s:au2,s:au3,s:chipx,s:chipy,l:tdetx,
l:tdety,s:detx,s:dety,s:x,s:y,s:pha,s:sumamps,s:chip_id,l:status}) event format definition string
         (mode = ql)