CalDB 188.8.131.52 Public Release Notes
Public Release Date: 09 July 2020
CalDB 184.108.40.206 is an upgrade to the Chandra CalDB, which includes the following items:
CalDB 220.127.116.11 includes CalDB 4.9.2, which was installed in Standard Data Processing (SDP) on 06 July 2020, but not released to the public at that time.
For the CIAO 4.12 / CalDB 18.104.22.168 release notes see How CalDB 22.214.171.124 Affects Your Analysis.
II. SUMMARY OF CHANGES
CalDB 126.96.36.199 is a patch release to CalDB version 4.9.2, which includes modifications to the headers of the above ACIS BKGRND files. The most important change to each file is a modification to the CBD30001 boundary condition, which is for the focal plane temerpature, FP_TEMP. The boundary condition has been changed from 'FP_TEMP(151.16-164.16)K' to 'FP_TEMP(148.15-168.16)K'. This expands the file selection range for FP_TEMP from (-121.99C - -108.99C) to (-125.0C - -104.99C). This change is being made to the above files to allow them to be selected using acis_bkgrnd_lookup when working on OBS_IDs with warmer ACIS FP_TEMP settings.
Given the inevitable warming of the Chandra spacecraft with age, maintaining the ACIS focal plane at -120C throughout the full available orbital period (even with excluding the radiation zone passages) has become increasingly difficult or even impossible. To maintain the science observation schedule, CXC Mission Planning has gotten approval for warmer FP_TEMPs (up to -109C nominally) to be used for science observations, despite the lack of any new high-temperature calibrations in CalDB. Hence, the FP_TEMP boundary conditions for CalDB files need to be expanded.
CIAO contributed tool: acis_bkgrnd_lookup
CIAO Data Preparation thread: Analysing the ACIS Background with the "Blank-Sky" Files