CalDB Public Release Notes Version: 2.29 CalDB Date: 2004-11-18T17:00:00 Public Release expected 11/19/2004 at 10:00 EST SDP Release anticipated 11/18/2004 at 20:00 EST I. INTRODUCTION CalDB 2.29 is a small but significant upgrade for ACIS users because it includes the EPOCH 18 and 19 updates for the T_GAIN (time-dependent gain) correction calibration data. This upgrade is neutral for HRC users. CalDB 2.29 impacts both CIAO data analysis and Standard Data Processing (SDP). Details of the ACIS calibration upgrades are provided below. II. SUMMARY OF CHANGES A. ACIS T_GAIN upgrades for EPOCH 18 (FEB-MAY 2004) and 19 (MAY-AUGUST 2004) Directory: $CALDB/data/chandra/acis/bcf/t_gain/ Filenames: acisD2004-02-01t_gainN0003.fits (EPOCHs 17 & 18) acisD2004-05-01t_gainN0003.fits (EPOCHs 18 & 19) acisD2004-11-01t_gainN0002.fits (EPOCH 19 noninterpolated) EPOCHS 18 and 19 corrections for the time-dependent gain are now available. Users in particular who have Oxygen emission lines in their data may wish to re-process their L1 events files, and reapply the t_gain correction once CalDB 2.29 is installed locally in their systems. HOWEVER, note that unless you are fitting a spectra with oxygen emission lines, the gain refinement is unlikely to have an effect on the spectrum larger than the uncertainties in determining the gain. See the Why page link: http://cxc-test.harvard.edu/ciao3.1/why/acistgain.html#calupdate for details and illustrations of the significance of these upgrades. Tools affected: DS and CIAO acis_process_events Threads affected: See the analysis guide ""ACIS Data Preparation" http://cxc.harvard.edu/ciao/guides/acis_data.html In particular see the threads: "Apply the Time-Dependent ACIS Gain Correction" http://cxc.harvard.edu/ciao/threads/acistimegain/ "Apply the ACIS CTI Correction" http://cxc.harvard.edu/ciao/threads/acisapplycti/ B. ACIS -120C gain and FEF files repaired (CCD-9, Node 2, Tile 19) Location: $CALDB/data/chandra/acis/bcf/gain/ Filenames: acisD2000-01-29gainN0004.fits (non-cti cases) acisD2000-07-04gainN0004.fits acisD2000-07-06gainN0004.fits acisD2000-08-12gainN0004.fits acisD2000-01-29gain_ctiN0002.fits (CTI-corrected) acisD2000-01-29p2_gain_ctiN0002.fits (CTI-corr. with S1 gain improvement) The ACIS calibration group has detected a significant, but generally inconsequential corruption of data in the ACIS gain and FEF files for -120C operating temperature, specifically for a single tile on the ACIS-9 chip, to wit CCD_ID=9, Node=2, Tile=19. The corruption has been identified, and the data have been corrected in the files specified above. TOOLS AFFECTED: DS/CIAO acis_process_events Threads affected: Users should note that the changes to the above files are generally unnoticeable by almost all users, because it is on a generally unused portion of CCD - 9, an end chip in the ACIS-S array. See "ACIS Data Preparation" http://cxc.harvard.edu/ciao/guides/acis_data.html In particular see the threads for: "Create a New Level=2 Event File" http://cxc.harvard.edu/ciao/threads/createL2/ "Apply an ACIS Gain Map" http://cxc.harvard.edu/ciao/threads/acisgainmap/ III. Technical Details A. EPOCH 18 and 19 T_GAIN additions The new CalDB files included in this release: Filenames: acisD2004-02-01t_gainN0003.fits (EPOCHs 17 & 18) acisD2004-05-01t_gainN0003.fits (EPOCHs 18 & 19) acisD2004-11-01t_gainN0002.fits (EPOCH 19 noninterpolated) contain two different epochs (three month epochs are used for T_GAIN) of calibration data so that the system may interpolate between them across the time period of applicability of the files. Hence in the listing above, the file actually contains the epochal correction tables corresponding to that period and the one following. The interpolation limit dates are included in the file headers. The new epochal tables, for reference, but NOT for use in the CALDB, are to be found online in the contributed software page. The new filenames are corrgain2004-05-01.fits (EPOCH 18) corrgain2004-08-01.fits (EPOCH 19) B. REPAIRS to -120C GAIN and FEF files Recent Cal group work on ACIS CTI corrections for ACIS chip 9 (-120C) has revealed an error in the gain and response tables for a single infrequently- used tile in Node 2 of that chip. The error occurred originally in version 2 of the -120C gain files, when the energy range of the FI chips was expanded from the original 0.277 - 9.886 keV to the current 0.1 - 11.0 keV range. The error occured only for the chip, node, and tile specified above. However the corrupted tile data have been propagated to a) the time-dependent gain files for -120C during Summer 2000, b) the new CTI-corrected -120C gains and c) special phase-2 response gain files as well. Additionally the -120C FEFs for the CTI-corrected as non-CTI corrected cases show the error, since currently CHIP 9 is NOT CTI-corrected at all in our releases. Hence the same data were used in both FEF files in order to make them complete datasets for ACIS. The errant FEF data for CCD-9, Node 2, Tile 19 are visible and indeed obvious in the extended ECD tables for that location. For the gains, the gain table for that location also clearly shows the error in a single location for each of the 30 energies included. The new tables will be posted in the Cal. web page area as soon as reasonably possible.