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Last modified: 28 October 2016


CalDB 4.7.2 Public Release Notes

Public Release Date: 31 MAY 2016

SDP Installation Date: 2016-05-31T21:28:27 (UTC)


CalDB 4.7.2 is an upgrade to the Chandra CalDB, which includes the following items:

  • Retraction of ACIS GRADE file N0005
  • Altered ACIS QE_CC file selection

For the CIAO 4.8 / CalDB 4.7.2 release notes see How CalDB 4.7.2 Affects Your Analysis.


A. Retraction of ACIS GRADE file N0005

Location: $CALDB/data/chandra/grade/
Filename of file to be removed from the distribution: acisD2009-11-01gradeN0005.fits
Filename of file to be used for all datasets: acisD1996-11-01gradeN0004.fits

As of the date 2009-11-01T00:00:00, flight grade "66" events for both GRADED or FAINT CC-mode observations began to be telemetered from the satellite; before that date all of these events had been excluded from telemetry for the CC-modes, so they had not been available at all for CTI correction, delivery, or exclusion. It was recognized that some of these events, at least in CC33_FAINT datamode, could be recovered as real X-ray events via the CC-mode CTI corrector, released in CIAO 4.8 in December 2015.

The ACIS GRADE file version N0005 above was introduced into Standard Data Processing on 29 October 2014, with the installation of DS10.4 and CalDB 4.6.4. Grade file N0005 has an added extension designated for GRADED CC-MODE only, which maps all flight grade "66" events to ASCA Grade "2", which are not filtered in Level 2 processing, meaning that all these events are retained in L2 rather than excluded for the GRADED CC-mode case. This new grade file (which goes into effect on the same date as the CC-mode telemetry change above) was then released to the public with CIAO 4.7 and CalDB 4.6.5 in December of 2014.

With the advent of CIAO 4.8, users of the GRADED CC-mode data have identified that the "G66" events add mainly background noise to these observations, and should be filtered out rather than remapped to a passable ASCA grade. Note that in GRADED datamodes, CTI correction is not availabe for the BI chips such as ACIS-S3, where most of these "G66" events occur. Hence it has been decided that the N0005 GRADE file must be retracted from CalDB, and that the old mapping assigning these events to ASCA Grade "7" should be re-implemented for GRADED CC-modes that include the "G66" events.


DS and CIAO level 1 (re)processing tool acis_process_events
Also: CIAO reprocessing script chandra_repro


Reprocessing Data to Create a New L2 Events File

B. Altered ACIS QE_CC file selection

Location: $CALDB/data/chandra/qe/
Filenames: acisD1997-04-17qeN0006.fits

The first ACIS QE file listed above is the standard QE that has been in use for ACIS observations since CIAO and CalDB 2.0 were released in December of 2001, very early in the mission. The second file is the modified ACIS QE specifically for the CC-modes, which is to be used when the flight grade "66" events are excluded from the data. This modified QE (called QE_CC hereafter) was introduced in CalDB 4.7.0 in December 2015, with CIAO version 4.8. At that time, it was designated for use with all CC-mode data where the "G66" events had been excluded from telemetry, that is, before (UTC) 2009-11-01T00:00:00.

Because these "G66" events have since been found to introduce mainly background noise in GRADED CC-mode data (see Item A. Retraction of ACIS GRADE file N0005 above), we now recommend excluding them from GRADED CC-mode data in ALL cases. Hence in this CalDB 4.7.2 release, the ACIS index has been altered to have the QE_CC file selected automatically in for the GRADED CC-mode.

See the ACIS Continuous-Clocking Mode why page for more information.


The ACIS QE_CC file above would be used by CIAO tools implemented with the "ARDLIB" analysis reference data manager . For GRADED CC-mode/GRATING observations, the script fullgarf is probably the most relevant.


HETG/ACIS-S Grating Spectra

LETG/ACIS-S Grating Spectra