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Last modified: 24 March 2022

URL: https://cxc.cfa.harvard.edu/caldb/downloads/Release_notes/CALDB_v4.9.7.html

CalDB 4.9.7 Public Release Notes

Public Release Date: 24 MAR 2022

SDP Installation Date: 2022-03-16T20:22:35 (UTC)


I. INTRODUCTION

CalDB 4.9.7 is an upgrade to the Chandra CalDB, which includes the following items:

For the CIAO 4.14 / CalDB 4.9.7 release notes see How CalDB 4.9.7 Affects Your Analysis.

II. SUMMARY OF CHANGES

A. ACIS T_GAIN Epochs 87+88

Location: $CALDB/data/chandra/acis/t_gain/
Filenames: acisD2021-05-02t_gainN0008B.fits   85+86 finalized   GRADED
acisD2021-05-02t_gainN0008.fits   85+86 finalized   non-GRADED
acisD2021-11-01t_gainN0002.fits   87+88 provisional   GRADED
acisD2021-11-01t_gain_biN0002.fits   87+88 provisional   non-GRADED

The ACIS Calibration Team has generated time-dependent gain (T_GAIN) corrections from onboard External Calibration Source (ECS) data taken during the period of 01 August 2021 through 31 Jan 2022 (Epochs 87+88). With this release it is now possible to finalize the T_GAIN for the previous bi-epochal period (Epochs 85+86, Feb 2021 through July 2021). These updates are included in the files above with effecive dates 2021-11-01T00:00:00 (provisional) and 2021-05-02T12:00:00 (finalized) respectively.

This release affects all ACIS observations taken since 2021-05-02T12:00:00, 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.

See the ACIS Time-dependent Gain why page for a more basic explanation of the time-dependent gain correction.

As indicated in Item B below, the FP_TEMP boundary condition for current science observations (ORs) is being changed to 'FP_TEMP(147.15-178.16)K'. The four new files above have this boundary condition so specified for ORs (OBS_MODE != SECONDARY).

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. New ACIS FP_TEMP Upper/Lower Limits

The ACIS focal plane temperature continues to drift upwards as the mission proceeds and the spacecraft ages. The ACIS Calibration Team has determined that calibrations for warmer operating temperatures (FP_TEMP in the event list file headers) will be needed in the very near future. In light of this determination, the Chandra CalDB Manager has elected to implement and expanded FP_TEMP boundary condition range for any calibration files that would apply to current and any future ACIS observations runs (ORs). This will allow the CalDB to provide existing calibrations for otherwise-out-of-range observations, in both CIAO and in SDP, until appropriate new calibrations can be provided from those warmer datasets.

Hence, in the file headers for the appropriate CalDB files, the new FP_TEMP boundary condition will be set as FP_TEMP(147.15-178.16)K, or -126.0C to -94.99C. This will apply to currently applicable ACIS BADPIX, BKGRND, CTI, DET_GAIN, FEF_PHA, OSIP, P2_RESP, and QEU CalDB files. The details including specific filenames, effective dates, CBD keywords, and previous vs new value settings are included in the Section III.B Technical Details section below.

This change will not affect any use of the CalDB for previous or recently-taken observations. Users should however check the V&V reports for future ACIS calibration observations for warnings concerning high FP_TEMP values, to evaluate whether or not use or inclusion of these warmer ACIS observations in their analysis will affect their results.

PIPELINES/TOOLS AFFECTED:

None.

THREADS AFFECTED:

None.

III. TECHNICAL DETAILS

A. ACIS T_GAIN Epochs 87+88

The general description and method of derivation for the ACIS T_GAIN are given in the memorandum posted on ACIS Calibrationweb page http://cxc.harvard.edu/cal/Acis/Cal_prods/tgain/index.html. However, additional steps have been added to the derivation procedure, due to the ever poorer statistics that are attainable from the ECS due to the source's diminishing flux levels. In particular, the ACIS calibration team has used trends from previous epochs (when more ECS flux was available) to "nudge" their more recent results to provide more predictable time-dependent gain corrections. The method is to combine earlier epochal data with current (i.e. new) epochal data to generate a 12-month average for T_GAIN corrections, and use the trends form the 12-month averages to modify the 6-month averages, resulting in a smoother correction with better statistical support.

The data are increasingly noisy as the ECS flux decreases with the age of the spacecraft. As a result the ACIS team is has selectively increased the range of acceptable operating focal plane temperatures (FP_TEMP values) for all of the 10 chips in order to include more events for better statistics in the T_GAIN correction values. This expanded range is 151.96K to 154.96K.

Long term trends for chips I3 and S3 are plotted below in Figures 1a and b, through Epoch 88, which includes the latest release. The chip locations for these plots are given in the respective labels above the plots. The chip locations selected are near the aimpoints. The full CTI corrections have been applied to the data in both figures. While some fluctuations have occurred recently in the results for the Ti and Mn lines of the ECS for I3 in particular, there is nothing out-of-expectation for the newest datasets. The fluctuations in the traces are due to counting statistics.

supporting/i3_tgain_trends_epochs1-88.gif
Fig. 1a: Long-term T_GAIN correction tgain_trends at the ACIS-I3 aimpoint,
for specific ECS line energies, from Epoch 1 to Epoch 86.
supporting/s3yesCTI_tgain_trends_epochs1-88.gif
Fig. 1b: Long term T_GAIN correction tgain_trends at the aimpoint of ACIS-S3,
for specific ECS line energies, from Epoch 1 to Epoch 86.

B. New ACIS FP_TEMP Upper/Lower Limits

The following table gives the specific CalDB file types and directory locations, the filenames, block numbers, effective dates, calibration boundary (CBD) keyword names, and the old and new CBD keyword values that have been assigned to those files and block numbers. All of these changes appear in the latest ACIS branch CalDB index file as well.

CODENAME
Directory
FILENAME BLOCK(s) Effective Date
CVSD*
FP_TEMP
KEYWORD
Old Value New Value
BADPIX
$CALDB/data/chandra/acis/badpix/
acisD2000-11-28badpixN0004.fits
acisD2000-11-28badpixN0004B.fits
2-11 2020-07-01T00:00:00 CBD10002 FP_TEMP(148.15-168.16)K FP_TEMP(147.15-178.16)K
CTI
$CALDB/data/chandra/acis/cti/
acisD2002-08-01ctiN0009B.fits 2-10 2020-07-01T00:00:00 CBD10002 FP_TEMP(148.15-168.16)K FP_TEMP(147.15-178.16)K
acisD2020-01-01ctiN0009.fits 2-14 2020-07-01T00:00:00 CBD10002 FP_TEMP(148.15-168.16)K FP_TEMP(147.15-178.16)K
DET_GAIN
$CALDB/data/chandra/acis/det_gain/
acisD2000-01-29gain_ctiN0005.fits 2 2020-07-01T00:00:00 CBD10002 FP_TEMP(148.15-168.16)K FP_TEMP(147.15-178.16)K
acisD2000-01-29gain_ctiN0008.fits 2 2020-07-01T00:00:00 CBD20003 FP_TEMP(148.15-168.16)K FP_TEMP(147.15-178.16)K
acisD2000-01-29gainN0005.fits 2 2020-07-01T00:00:00 CBD10005 FP_TEMP(148.15-168.16)K FP_TEMP(147.15-178.16)K
FEF_PHA
$CALDB/data/chandra/acis/fef_pha/
acisD2000-01-29fef_pha_ctiN0004.fits 2 2020-07-01T00:00:00 CBD10002 FP_TEMP(148.15-168.16)K FP_TEMP(147.15-178.16)K
acisD2000-01-29fef_phaN0005.fits 2 2020-07-01T00:00:00 CBD10002 FP_TEMP(148.15-168.16)K FP_TEMP(147.15-178.16)K
OSIP
$CALDB/data/chandra/acis/osip/
acisD2000-01-29osip_ctiN0005.fits 2 2020-07-01T00:00:00 CBD10002 FP_TEMP(148.15-168.16)K FP_TEMP(147.15-178.16)K
acisD2000-01-29osip_ctiN0006.fits 2 2020-07-01T00:00:00 CBD10002 FP_TEMP(148.15-168.16)K FP_TEMP(147.15-178.16)K
acisD2000-01-29osipN0006.fits 2 2020-07-01T00:00:00 CBD10003 FP_TEMP(148.15-168.16)K FP_TEMP(147.15-178.16)K
P2_RESP
$CALDB/data/chandra/acis/p2_resp/
acisD2000-01-29p2_respN0005.fits 2-5
6
2020-07-01T00:00:00 CBD30002
CBD10002
FP_TEMP(148.15-168.16)K FP_TEMP(147.15-178.16)K
acisD2000-01-29p2_respN0008.fits 2-5
6
2020-07-01T00:00:00 CBD30002
CBD10002
FP_TEMP(148.15-168.16)K FP_TEMP(147.15-178.16)K
QEU
$CALDB/data/chandra/acis/qeu/
acisD2010-02-01qeuN0005B.fits 2-11 2020-07-01T00:00:00 CBD30002 FP_TEMP(148.15-168.16)K FP_TEMP(147.15-178.16)K
acisD2010-02-01qeuN0007.fits 2-11 2020-07-01T00:00:00 CBD30002 FP_TEMP(148.15-168.16)K FP_TEMP(147.15-178.16)K
BKGRND
$CALDB/data/chandra/acis/bkgrnd/
acis0iD2012-01-01bkgrnd_ctiN0002.fits 2 2012-12-01T00:00:00 CBD30001 FP_TEMP(148.15-168.16)K FP_TEMP(147.15-178.16)K
acis1iD2012-01-01bkgrnd_ctiN0002.fits 2 2012-12-01T00:00:00 CBD30001 FP_TEMP(148.15-168.16)K FP_TEMP(147.15-178.16)K
acis2iD2012-01-01bkgrnd_ctiN0002.fits 2 2012-12-01T00:00:00 CBD30001 FP_TEMP(148.15-168.16)K FP_TEMP(147.15-178.16)K
acis2sD2012-01-01bkgrnd_ctiN0002.fits 2 2012-12-01T00:00:00 CBD30001 FP_TEMP(148.15-168.16)K FP_TEMP(147.15-178.16)K
acis3iD2012-01-01bkgrnd_ctiN0002.fits 2 2012-12-01T00:00:00 CBD30001 FP_TEMP(148.15-168.16)K FP_TEMP(147.15-178.16)K
acis3sD2012-01-01bkgrnd_ctiN0002.fits 2 2012-01-01T00:00:00 CBD30001 FP_TEMP(148.15-168.16)K FP_TEMP(147.15-178.16)K
acis5sD2009-09-21bkgrndN0002.fits 2 2009-09-21T00:00:00 CBD30001 FP_TEMP(148.15-168.16)K FP_TEMP(147.15-178.16)K
acis5sD2012-01-01bkgrnd_ctiN0002.fits 2 2012-12-01T00:00:00 CBD30001 FP_TEMP(148.15-168.16)K FP_TEMP(147.15-178.16)K
acis6iD2012-01-01bkgrnd_ctiN0002.fits 2 2012-12-01T00:00:00 CBD30001 FP_TEMP(148.15-168.16)K FP_TEMP(147.15-178.16)K
acis6sD2012-01-01bkgrnd_ctiN0002.fits 2 2012-12-01T00:00:00 CBD30001 FP_TEMP(148.15-168.16)K FP_TEMP(147.15-178.16)K
acis7sD2009-09-21bkgrndN0002.fits 2 2009-09-21T00:00:00 CBD30001 FP_TEMP(148.15-168.16)K FP_TEMP(147.15-178.16)K
acis7sD2012-01-01bkgrnd_ctiN0002.fits 2 2012-12-01T00:00:00 CBD30001 FP_TEMP(148.15-168.16)K FP_TEMP(147.15-178.16)K
acis8sD2012-01-01bkgrnd_ctiN0002.fits 2 2012-12-01T00:00:00 CBD30001 FP_TEMP(148.15-168.16)K FP_TEMP(147.15-178.16)K
acis0D2009-09-21bgstow_ctiN0002.fits 2 2009-09-21T00:00:00 CBD30001 FP_TEMP(148.15-168.16)K FP_TEMP(147.15-178.16)K
acis1D2009-09-21bgstow_ctiN0002.fits 2 2009-09-21T00:00:00 CBD30001 FP_TEMP(148.15-168.16)K FP_TEMP(147.15-178.16)K
acis2D2009-09-21bgstow_ctiN0002.fits 2 2009-09-21T00:00:00 CBD30001 FP_TEMP(148.15-168.16)K FP_TEMP(147.15-178.16)K
acis3D2009-09-21bgstow_ctiN0002.fits 2 2009-09-21T00:00:00 CBD30001 FP_TEMP(148.15-168.16)K FP_TEMP(147.15-178.16)K
acis5D2009-09-21bgstow_ctiN0002.fits 2 2009-09-21T00:00:00 CBD30001 FP_TEMP(148.15-168.16)K FP_TEMP(147.15-178.16)K
acis6D2009-09-21bgstow_ctiN0002.fits 2 2009-09-21T00:00:00 CBD30001 FP_TEMP(148.15-168.16)K FP_TEMP(147.15-178.16)K
acis7D2009-09-21bgstow_ctiN0002.fits 2 2009-09-21T00:00:00 CBD30001 FP_TEMP(148.15-168.16)K FP_TEMP(147.15-178.16)K