CALDB RELEASE NOTES Version: 2.27 CALDB Effective Date: 2004-07-01T13:00:00 Concurrent with CIAO 3.1 Release I. Introduction CalDB 2.27 contains an essential element for CIAO version 3.1: the ACIS T_GAIN file. Additionally, there are new HETGS and LETGS first order LSF parameter (LSFPARM) files with zero randomization (RAND_TG=0.0). CIAO 3.1 includes a modified ardlib.par which selects the correct type of LSFPARM file based on whether or not your data have pixel randomization turned on. II. Summary of Changes and Additions A. ACIS T_GAIN time-dependent gain correction files We have determined that there is a time-dependent variation in the effective gain of the ACIS chips due to the slowly increasing CTI due to on-orbit exposure. The new files contain the PHA correction tables to be used to compensate for this effect. The files are version 3, but are the first to be publicly released. Directory: $CALDB/data/chandra/acis/bcf/t_gain/ (new dir) Filnames: (18 total files, and more to be added quarterly) acisD2000-01-29t_gainN0003.fits acisD2000-05-01t_gainN0003.fits acisD2000-08-01t_gainN0003.fits acisD2000-11-01t_gainN0003.fits acisD2001-02-01t_gainN0003.fits acisD2001-05-01t_gainN0003.fits acisD2001-08-01t_gainN0003.fits acisD2001-11-01t_gainN0003.fits acisD2002-02-01t_gainN0003.fits acisD2002-05-01t_gainN0003.fits acisD2002-08-01t_gainN0003.fits acisD2002-11-01t_gainN0003.fits acisD2003-02-01t_gainN0003.fits acisD2003-05-01t_gainN0003.fits acisD2003-08-01t_gainN0003.fits acisD2003-10-19t_gainN0003.fits acisD2003-11-18t_gainN0003.fits acisD2004-01-01t_gainN0003.fits acisD2004-02-01t_gainN0002.fits Tool affected: CIAO/DS pipeline ACIS L1 "acis_process_events," activated by setting the new acis_process_events.par parameter "apply_tgain" to "yes." Relevant Thread: "Apply the Time-Dependent ACIS Gain Correction" http://cxc.harvard.edu/ciao/threads/acistimegain/ B. ACIS phase 2 gain v1 There is a new gain function for ACIS chips 0-3, and 5-7 which better represents the Si-K region. Additionally, it contains a much more accurate gain table for the S1 (ACIS-5) chip. Currently this file should only be used for ACIS/grating observations, with the CTI-correction ON, and the file must be hand-selected. Directory: $CALDB/data/chandra/acis/bcf/gain/ Filename: acisD2000-01-29p2_gain_ctiN0001.fits Tool affected: "acis_process_events" with parameter gainfile set to $CALDB/data/chandra/acis/bcf/gain/acisD2000-01-29p2_gain_ctiN0001.fits C. HETGS and LETGS first-order no-randomization LSF Parameter files As of the installation of DS 7.3.0 in pipeline operations, scheduled for June 2004, grating pixel randomization will be turned off, and the value of keyword RAND_TG will be set to 0.0 pixels. The following LSF parameter files have been rebuilt with this prescription. They will be automatically selected for the cases where RAND_TG is set to ZERO in the PHA2 and EVT2 data file headers. HETG/ACIS-S: Directory: $CALDB/data/chandra/tel/grating/hetg/cpf/lsf/ Filenames: acisheg-1D1999-07-22lsfparmN0004.fits acisheg1D1999-07-22lsfparmN0004.fits acismeg-1D1999-07-22lsfparmN0004.fits acismeg1D1999-07-22lsfparmN0004.fits LETG/HRC-S: Directory: $CALDB/data/chandra/tel/grating/letg/cpf/lsf/ Filenames: hrcsleg-1D1999-07-22lsfparmN0003.fits hrcsleg1D1999-07-22lsfparmN0003.fits Tools affected: CIAO "mkgrmf". Relevant Threads: "Create Grating RMFs for ACIS-S Observations" http://cxc.harvard.edu/ciao/threads/mkgrmf_aciss/ "Create Grating RMFs for HRC-S Observations" http://cxc.harvard.edu/ciao/threads/mkgrmf_hrcs/ D. GTI LIMITS updates for ACIS and HRC ACIS: $CALDB/data/chandra/acis/bcf/gtilim/ FILENAMES: acisD1999-07-22gtilimN0006.fits acisD1999-07-22gtilim_secN0005.fits acisD2002-11-15gtilimN0003.fits HRC: $CALDB/data/chandra/hrc/bcf/gtilim/ hrciD1999-07-22gtilimN0006.fits hrciD1999-07-22gtilim_secN0005.fits hrciD1999-10-04gtilimN0006.fits hrciD1999-10-04gtilim_secN0005.fits hrciD2002-11-15gtilimN0003.fits hrcsD1999-07-22gtilimN0006.fits hrcsD1999-07-22gtilim_secN0005.fits hrcsD2002-11-15gtilimN0003.fits Tools affected: DS 7.3.0 MTL pipeline processing, "mtl_build_gti" III. Technical details A. ACIS T_GAIN time-dependent gain correction files We have determined that the effective gains of the various ACIS chips have been degrading since launch. We have calibrated this effect for chips 0, 1, 2, 3, 5, 6, 7. Chips 4, 8, and 9 are not calibrated and the correction is not effective for those chips. The correction is done by artificially shifting the PHA values by an interpolated correction factor derived from quarterly gain correction tables, stored in the new CalDB files. Each file contains two gain correction tables used to interpolate the correction values to be applied to each dataset. See the memorandum "Corrections for time-dependence of ACIS gain" http://hea-www.harvard.edu/~alexey/acis/tgain/ B. ACIS P2_RESP GAIN version 1 Technical details for the new gain data are TBR on the Cal web pages. For now, the document section: https://icxc.harvard.edu/calco/ard_updates/ECR/supporting/gain.pdf contains an excellent discussion of the ACIS gain functions. C. LSFPARM files with RAND_TG=0.0 See the memorandum "Evaluation of the Quality of HETG/ACIS-S LSFPARM file for unrandomized event datasets," http://space.mit.edu/ASC/docs/memo_lsf_ha_1.1.ps.gz See the memorandum "Evaluation of the Quality of LETG/HRC-S LSFPARM file for unrandomized event datasets," http://space.mit.edu/ASC/docs/memo_lsf_lh_1.1.ps.gz See the web page http://space.mit.edu/CXC/LSFX/index.html for construction and verification details for LSF parameter files. D. GTI LIMITS ACIS GTI LIMITS changes: The following ACIS related GTI limit is added: From: To: (((READMODE:1=="TIMED")&&(EXPNO:1>2)) || ((READMODE:1=="CONTINUOUS")&&(EXPNO:1>3))) Justification: The GTIs for ACIS data now erroneously include frame numbers (EXPNO) 2 and higher, because these frame are in exr0 and stat1 files. However, no science data is telemetered for frame 2 in TIMED mode, or frames 2 and 3 in CC mode. These frames should be excluded from good time. HRC GTI LIMIT changes: The following HRC related GTI limit is changed: From: (STATUS:1==X1F,X2F,X3F,X4F,X5F) To: ((STATUS:1==X1F)&&(STATUS:1==X2F)&&(STATUS:1==X3F)&&(STATUS:1==X4F)&&(S TATUS:1==X5F)) Justification: The revisions to hrc_calc_deadtime that implements the HRC rate scalars recomputation defines 3 new bad-status bits: 0x08: Total or valid event count < 0 0x10: Total or valid event count in SS0a record saturated (>65535) 0x20: Time difference between adjacent SS0a records > user-defined limit (default = 5 sec.) GTIs should now exclude times when any of these new bits are set as well as the existing status bit checks. These bits correspond to X3F,X4F,X5F in the gtilim files. Addtionally: mtl_build_gti incorrectly interpreted a filter of the form XF,XF to mean "bit false OR bit false" instead of "bit false AND bit false" as documented. Explicitly checking each bit using the alternate syntax is interpreted correctly by mtl_build_gti.