CalDB 4.4.9 Public Release Notes
INTERNAL RELEASE ONLY!
SDP Installation Date: 2012-03-29T00:00:00 (UTC)
CalDB 4.4.9 is an upgrade to the Chandra CalDB, which includes the following items:
- HRC-S GTI LIMITS for New HV Setting
NOTE: This CalDB release has zero affect on analysis with CIAO.
II. SUMMARY OF CHANGES
Due to rather severe gain and quantum efficiency loss with time on the HRC-S detector array, the HRC Team, with approval of the Chandra Flight Director Board, has elected to increase the high voltage on the device to allow for some recovery thereof. Hence, the HV settings in the HRC-S GTI_LIM files must be adjusted to accommodate the change for any observations taken on or after the date of the HV adjustment. The above file include the appropriate GTI Limits changes as specified by the HRC-S calibration team.
See the GTI Definition page for more information.
HRC Level 1 pipeline tool mtl_build_gti: Note that mtl_build_gti works differently in the pipeline than it does in CIAO, because in the pipeline it is run twice after the L1 tool mtl_build_table is run to build the seed version of the MTL1 file. The first time through, mtl_build_gti queries the CalDB to bring in the first set of GTI limits from the CalDB, based on the instrument (INSTRUME), detector (DETNAM), observation date (DATE-OBS and DATE-END), and observation mode (OBS_MODE) values for the observation in question. The above HRC-S GTI_LIM files are examples of CalDB GTI_LIM files that would be selected for current HRC-S observation processing. The filename is stored as keyword LIMFILE1 in the header of the "GTI_S" block of the MTL1 file in secondary data products for a given observation, and the limits listed in the GTI_LIM file are seeded into the LIMITS extension (Block 4) of the MTL1 file. The subsequent run of mtl_build_gti produces the FLT1 secondary products file, whence the GTI limits extension(s) in HRC-S observations events files are derived.
III. TECHNICAL DETAILS
The flight software has been patched to change the programmatic MCP HV settings for the HRC-S. The HV will be raised on both the bottom and top MCPs. This will result in a needed change to the HV level check used to determine GTIs.
The previous HV setting check was:
Based on pre-launch lab measurements and the small amount of data collected during the recent on-orbit test (ObsID 62687) this has been changed to:
The software patch has been uploaded prior to an HZ43 calibration observation scheduled for early April. There were two "soak" observations done at the planned higher voltage prior to this calibration observation which have provided for an opportunity to test the updated CALDB file in special processing.
The Chandra Flight Director Board has approved the proposed increase in the HRC-S MCP High Voltage
settings. The new HV setting was approved for the afternoon pass of 29 Mar 2012, and hence was in effect
on and subsequent to that date. There are in fact two HRC-S GTI_LIM files that are affected by this change,
such that Standard Processing MTL level 1 pipeline will not run the new data, unless the GTI_LIM files are
updated with the new HV settings. One is selected when collecting HRC-S engineering data (OBS_MODE=SECONDARY)
and one for general observations (OBS_MODE=POINTING, RASTER, SCAN, or SLEW). Both the new files, with
effective date 2012-03-29T00:00:00, have the updated specification for the HRC-S HV settings in the FITS
Binary Table in Extension 1, specifically:
whereas the older files each specify:
The change was necessary essentially immediately, because a new HRC-S OBS_ID (14252), with the new HV settings, was scheduled for Saturday, 31 Mar 2012, at 3:13PM local time.