CalDB 4.9.8 Public Release Notes
Public Release Date: 16 JUN 2022
SDP Installation Date: 2022-06-15T19:37:14 (UTC)
CalDB 4.9.8 is an upgrade to the Chandra CalDB, which includes the following items:
For the CIAO 4.14 / CalDB 4.9.8 release notes see How CalDB 4.9.8 Affects Your Analysis.
II. SUMMARY OF CHANGES
A. PCAD "CALALIGN" version N0010
The ASPECT Calibration Team has just recently generated new PCAD "ALIGN" files, orignally designated "CALALIGN", updating the existing file set in CalDB for the first time since year 2013. The above 18 files, separated in six-month intervals, each include modified aca_misalign and fts_misalign in order to improve absolute aspect solution accuracy. The new values were determined using Chandra observations of well-determined X-ray sources, and comparing those with the latest tabulated positions of their optical counterparts. A table containing the actual updated calibration products is included in the technical details linked to this section.
Aspect L1 pipeline tool asp_get_calib, which writes the acacal apect supporting data product.
CIAO THREADS AFFECTED:
None. PCAD CalDB files are not referenced by any CIAO software.
B. HRC-I Grating Angle Corrections
Improvements have been made for all three of the HRC-I/Grating angles (HEG, MEG, and LEG) in the PIXLIB GEOM file above in CalDB. The changes are small, but as illustrated in the associated Technical Details for this section, the apparent tilt in the grating dispersion versus wavelength across the HRC-I "axis" has been removed for all three grating arms. Users may apply these updates to archival HRC-I/Gratings observations using the chandra_repro script in CIAO.
CIAO 4.14 reprocessing tool chandra_repro; affects HRC-I/GRATING observations only.
C. HRC-S QE Uniformity version N0016
Another full upgrade is being released to the QEU calibration data sets for HRC-S listed above. As stated in the previous release of the HRC-S QEU's, the secular time variations in the HRC-S response are subsumed into these numerous QEU maps.
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 pipeline procedure "tg_mk_responses" 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.
For exposure-corrected imaging analysis with HRC-S, see the thread:
For grating spectroscopy with the LETG/HRC-S, see the thread:
D. PCAD "CALALIGN" old file header changes
The existing set of 49 PCAD ALIGN files with version N0008, extending in effective dates from the beginning of the mission until the end of year 2002, have had the Calibration Validity End Dates (CVED0001) and times (CVET0001) header keywords deleted from their Block 2 headers. These headers provide the single listing for each file in the PCAD branch CalDB index. The change is make these old files conform to the current standard for PCAD ALIGN CalDB specs in the Chandra CalDB. These changes have zero effect on current processing, and are listed here only for completeness.