CALDB INTERNAL RELEASE NOTES Version: 2.4 CALDB DATE: 2001-03-19T20:00:00 (Noon EST) Internal Release notes are available for viewing (CfA Only) at http://cxc.harvard.edu/caldb/version_release_notes.html NOTE: CALDB 2.4 is an internal SDP/HEAD release only. The updates included here will not be released to the public until the next CALDB update, to be released 04 June 2001, with CALDB 2.6. The upgrade of the Chandra CALDB to version 2.4 took place at 15:00 EST, on 19 March 2001. The FPTEST coefficients, part of the particle background and ghost-removal in HRC observations, have been optimized in time for REPRO II, wherein all HRC OBSIDS since launch date will be reprocessed. I. SUMMARY of CHANGES HRC-I/S event hyperbolic test (FPTEST) coefficients files. NEW FILENAMES: $CALDB/data/chandra/hrc/bcf/fptest/ hrciD1999-07-22fptestN0003.fits hrcsD1999-07-22fptestN0004.fits These files are used in "hrc_process_events", both in standard Level 1 processing and in the CIAO threads for regenerating HRC-I or -S events files. (See the threads page http://asc.harvard.edu/ciao/threads/hrcidegap.thread.html.) The event hyperbolic test is the key method for removing "ghost" images which result when certain events' positions are incorrectly determined in the HRC electronics. You can learn more about this specific correction from the CAL web page at http://asc.harvard.edu/cal/Links/Hrc/CIP/filter.html See also SS Murray, et al., "Event Screening for the Chandra X-ray Observatory High Resolution Camera (HRC)," available at http://hea-www.harvard.edu/HRC/calib/event_screening.ps II. TECHNICAL DETAILS The HRC IPI team has indicated that corrections and updates were needed to several values in the HRC-I and HRC-S FPTEST coefficients files. In some cases the U and V axis values were switched; in others improved values were provided. Here are the (new) specific values, for your edification: HRC-I: Axis B H A DELTAH U 0.3030 1.058 0.3110 0.035 V 0.2730 1.100 0.3050 0.035 HRC-S: Axis B H A DELTAH V 0.2480 1.071 0.2706 0.035 U 0.2620 1.018 0.2706 0.035 The value of DELTAH has been increased to .035 from .030 in all four cases for this most recent update. For HRC-S, the values needed to be switched between U and V axes. HRC-I and HRC-S observations will be reprocessed from Launch Date to include the most up-to-date event test coefficients and the latest degap corrections (HRC-I). Regenerating L1 events files with CIAO: CIAO users may execute the hrc_process_events thread immediately to take advantage of all the most recent improvements in HRC level one calibration data, but only after AFTER they have installed these updated FPTEST files. WARNING: If your HRC data have been processed with CALDB v2.4 or later version, do NOT use CALDB 2.3/CIAO 2.x to regenerate L1 files or re-execute degap corrections as you will degrade your output with earlier calibration data. To determine the CALDB version used in processing, use the following command: % dmlist header | grep CALDBVER