CalDB 4.12.2 Public Release Notes
Public Release Date: 19 Aug 2025
SDP Installation Date: 2025-08-15T15:00:00 (UTC)
I. INTRODUCTION
CalDB 4.12.2 is an upgrade to the Chandra CalDB, which includes the following items:
For the CIAO 4.17 / CalDB 4.12.2 release notes see How CalDB 4.12.2 Affects Your Analysis.
II. SUMMARY OF CHANGES
A. ACIS T_GAIN Upgrades Epochs 91-99
| Location: | $CALDB/data/chandra/acis/t_gain/ |
| Filenames: | acisD2021-11-01t_gainN0008B_revA.fits acisD2021-11-01t_gainN0008_revA.fits acisD2022-09-15t_gainN0008B.fits acisD2022-09-15t_gainN0008.fits acisD2023-03-01t_gainN0008B.fits acisD2023-03-01t_gainN0008.fits acisD2023-12-15t_gainN0008B.fits acisD2023-12-15t_gainN0008.fits acisD2024-10-15t_gainN0002B.fits acisD2024-10-15t_gainN0002.fits |
| Removed files: | acisD2019-05-02t_gainN0008B.fits acisD2019-05-02t_gainN0008.fits acisD2021-11-01t_gain_biN0002.fits acisD2021-11-01t_gainN0002.fits |
The ACIS Calibration Team has generated time-dependent gain (T_GAIN) corrections from (very weak) onboard External Calibration Source (ECS) data taken during the period of 01 Feb 2022 through 31 Jan 2025 (Epochs 91-99). The corrections derived from the weak ECS data have been modified using calibration obsevations of cosmic sources such as A1795, the Perseus Cluster, and E0102-72.3. With this release it has become necessary to revise (*_revA.fits) the previously finalized T_GAIN files for the previous bi-epochal period (Epochs 87+88, 01 November 2021 through 15 September 2022). These updates are included in the files above with effecive dates 2024-10-15T00:00:00 (provisional, versions N0002) and 2021-11-01T00:00:00 (revised, _revA.fits) respectively. Several multi-epochal files have been added for the intervening periods, including those for 2022-09-05T12:00:00, 2023-03-01T00:00:00, and 2023-12-15T12:00:00.
This release affects all ACIS observations taken since 2021-11-01T00:00:00, and users of any OBS_IDs with DATE-OBS later than that date are encouraged to reprocess their datasets. The degree of the corrections is similar to those of previous T_GAIN releases, and those analyzing narrow line-source data are the most likely to be affected signficantly. See the Section III.A technical details section below for further information regarding these specific file upgrades.
The files with the 'B' tag are to be used for GRADED and CC33_GRADED DATAMODE configurations, as needed, for their relevant effective periods.
See the ACIS Time-dependent Gain why page for a more basic explanation of the time-dependent gain correction.
PIPELINES/TOOLS AFFECTED:
ACIS Level 1 pipeline tool acis_process_events.
CIAO script chandra_repro uses acis_process_events to reprocess ACIS observation data.
THREADS AFFECTED:
Reprocessing Data to Create a New Level=2 Event File
B. HRC-S QEU Version N0022
| Location: | $CALDB/data/chandra/hrc/qeu/ |
| Filenames: | hrciD1999-07-22qeuN0002.fits hrcsD1999-07-22qeuN0022.fits hrcsD2000-01-01qeuN0022.fits hrcsD2001-01-01qeuN0022.fits hrcsD2002-01-01qeuN0022.fits hrcsD2003-01-01qeuN0022.fits hrcsD2004-01-01qeuN0022.fits hrcsD2005-01-01qeuN0022.fits hrcsD2006-01-01qeuN0022.fits hrcsD2007-01-01qeuN0022.fits hrcsD2008-01-01qeuN0022.fits hrcsD2009-01-01qeuN0022.fits hrcsD2009-09-15qeuN0022.fits hrcsD2010-09-14qeuN0022.fits hrcsD2012-03-29qeuN0022.fits hrcsD2012-10-05qeuN0022.fits hrcsD2013-09-21qeuN0022.fits hrcsD2015-02-17qeuN0022.fits hrcsD2016-02-22qeuN0022.fits hrcsD2016-07-29qeuN0022.fits hrcsD2017-01-25qeuN0022.fits hrcsD2017-06-06qeuN0022.fits hrcsD2017-09-27qeuN0022.fits hrcsD2018-01-20qeuN0022.fits hrcsD2018-05-27qeuN0022.fits hrcsD2018-09-27qeuN0022.fits hrcsD2019-02-25qeuN0022.fits hrcsD2019-08-23qeuN0022.fits hrcsD2020-01-18qeuN0022.fits hrcsD2020-07-23qeuN0022.fits hrcsD2021-05-14qeuN0022.fits hrcsD2021-09-03qeuN0022.fits hrcsD2022-09-09qeuN0022.fits hrcsD2023-09-08qeuN0022.fits hrcsD2024-03-04qeuN0022.fits hrcsD2024-07-12qeuN0022.fits hrcsD2024-09-20qeuN0022.fits hrcsD2024-11-07qeuN0022.fits hrcsD2025-03-16qeuN0022.fits |
The HRC Calibration Team has released a new HRC-S QEU file set, version N0022 which includes 38 new files. This includes one additional file from the N0021 set, effective on 2025-03-16, which is based on the June 2025 HZ43 observations. The decline in the net QE relative to the Nov 2024 file is minor, around -1%.
As usual, this set completely replaces the N0021 file set, which is now retired from the distribution and the index.
See the HRC-S QE/QEU why page for information on the current HRC-S QE and QE Uniformity. See the technical details section below for illustrations and details of the derivation of these new QE Uniformity corrections.
SDP Pipeline / CIAO SCRIPTS/TOOLS AFFECTED:
The SDP grating L2 pipeline tool "tg_mkresponse.py" is used to generate single-source GARFs and GRMFs for HRC-S/LETG observations, to be ingested onto the archive. This procedure uses the HRC-S QEU library as loaded from the ARDLIB.
See the CIAO script fluximage, which uses mkinstmap.
THREADS AFFECTED:
For exposure-corrected imaging analysis with HRC-S, see the thread:
For grating spectroscopy with the LETG/HRC-S, see the thread:
C. PCAD ACA-P DARK_CURR Updates #11
| Location: | $CALDB/data/chandra/pcad/dark_curr/ |
| Filenames: | acapD2025-05-12darkN0002.fits acapD2025-06-13darkN0002.fits acapD2025-07-08darkN0002.fits |
The CXC Aspect Team has generated an eleventh set of ACAP DARK_CURR files, including three new files, to support ACA background calculation and subtraction in the ASPECT L1 pipeline. The DARK_CURR files draw on an ever-growing database of ACA full field dark current data products which have been accumulated since the 1999:223 OAC dark current pixel map. Each version N0002 dark current fits file in the CALDB includes a 1024x1024 image with the processed full-field dark current map of the ACA CCD in e-/sec. Each file also includes header information with the ACA CCD temperature of the calibration, the reference date of the ACA dark current product, and the scale expected to be used to scale the calibration e-/sec to the effective e-/sec at the observed temperatures during observations.
The DARK_CURR files have effective dates (Cal Validity Start Date, or CVSD*) which are spaced ~2-6 weeks apart, as with their previously released datasets. The new files are effective as of the respective dates given in the filnames in the Description of Change section below. These new files extend the date coverage for archival observations through 2025-07-08T00:00:00, with the final file being the one that will be the default file in standard data processing (SDP) until the next release/extension.
PIPELINES/TOOLS AFFECTED:
PCAD L1 Pipeline tool asp_get_calib calls for the ASPECT CalDB files, including DARK_CURR.
THREADS AFFECTED:
None.
III. TECHNICAL DETAILS
A. ACIS T_GAIN Upgrades Epochs 91-99
The ACIS combined T_GAIN epochs e91, e93, e96, and e99, derived from the External Calibration Source (ECS) radiation zone data, reduced as per the recently-modified procedures, to generate the time-dependent gain correction tables for periods over 2022 2025. The data have been further modified using recent observations of several cosmic calibration sources A1795, Perseus Cluster, and E0102-72.3. The ACIS Calibration team has generated and tested new CalDB ACIS T_GAIN files, which are ready to be added to the Chandra calibration database and released to the public and to standard data processing (SDP).
B. HRC-S QEU Version N0022
The HRC-S QEU N0022 file set adds one additional QEU file, effective 2025-03-16T00:00:00, and based on two HZ43 observations from June 2025 (including OBS_ID 30696). The new file upstages the last file from the previous N0021 set, effective 2024-09-20T12:10 UTC based on the most recent HZ43 observations (28427, from June 2024, and 29452, from August 2024.) The wavelength-independent drop in the net QE from June 2024 about -1%.
The plots in Fig. 1 below give wevelength-dependent corrections applied to each file, with the black traces for S1, the red for S3.
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Fig 1: The CARMA models used for the HRC-S QEU N0022 file set from |
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