CALDB RELEASE NOTES Version: 2.6 CALDB Effective Date: 2001-06-01T19:59:00 (3:58pm EDT) I. Summary of Changes A. HRC-S DEGAP Version 2 Filename: hrcsD1999-07-22gapN0002.fits in $CALDB/data/chandra/hrc/bcf/degap/ B. -100C ACIS OSIP table, Version 5 Filename: acisD1999-08-13osipN0005.fits in $CALDB/data/chandra/acis/cpf/osip/ C. ACIS QE version 4, for use with LETG/ACIS-S only Filename: acisD1997-04-17qeN0004.fits in $CALDB/data/chandra/acis/bcf/qe/ File must be selected by hand for use in CIAO. D. GTI_LIM file changes Filenames: acisD1999-07-22gtilimN0003.fits in $CALDB/data/chandra/acis/bcf/gtilim/ hrciD1999-07-22gtilimN0003.fits hrciD1999-10-04gtilimN0003.fits hrcsD1999-07-22gtilimN0003.fits The only change here is that the altitude lower limit of 60,000 km, originally included to exclude radiation zone from giving good time intervals in any case, has been removed from the N0003 files. II. Technical Reports A. HRC-S Degap upgrade v2: This new degap correction file removes difficulties for imaging with HRC-S, caused by an inadequate degap specification in the N0001 file for low U and high U column numbers. This resulted in a non-correction for the degap in a number of CAL observations, and any observations with point sources near the long edges of the S2 plate. This new degap map is NOT a final solution, as the PSF performance is not yet what is expected for sources within a few arc minutes of the axis. Hence, while there is a significant improvement for edge point sources, it should clearly be possible to improve on the point source resolution with a better correction map, to be expected around August 1, 2001 (version 3). Thread affected: The new HRC-S degap correction thread. http://asc.harvard.edu/ciao/threads/hrcsdegap.thread.html B. -100C OSIP version 5: For OAC grating observations, the N0004 OSIP (order sorting and integrated probability) table is clipping events severely and asymmetrically between + and - orders. This is due to the onset of ACIS CTI problems in the FI chips between August 12, 1999 and August 28, 1999, when the first HETG/ACIS-S grating data of Capella were being taken. Public OBSIDs 1099, 1100, 1101, 1235, 1236, and 1237 were badly affected, losing 60% of counts in the negative 1st order over 12-16A of the MEG, and up to 85% of events at 14A in the HEG-1 order. By opening the negative acceptance angle in (grating order) x (order-wavelength) space in the first order, one is able to recover most of the symmetry, although the correction is still not perfect. What is literally needed is a better gain-response calibration during that ramping period of damage to ACIS near late August 1999. However this is not likely to come in the near future, so this file will have to do for now. Threads affected: mkgarf (mkgarf_acis) (CIAO) http://asc.harvard.edu/ciao/threads/mkgarf.hetgacis.html#osip http://asc.harvard.edu/ciao/threads/mkgarf.letgacis.html#osip Grating L1.5 with ACIS, aka tg_resolve_events (CIAO and SDP) http://asc.harvard.edu/ciao/threads/spectra.hetgacis.html#hetg.thread.B.Generate1.5.html http://asc.harvard.edu/ciao/threads/spectra.letgacis.html#letg.thread.B.Generate1.5.html C. ACIS QE version 4, user-selectable file: Details are posted at http://space.mit.edu/CXC/calib/letg_acis/ck_cal.html. For some time now we have known that residuals have remained in fits of continuum sources in LETG/ACIS observations near the carbon edge (3C273 for example). An attempt is being made to correct the residual with an as yet unaccounted-for enhancement of the Carbon-K edge absorption features, which has been consigned to the Optical Blocking Filter transmission. The CAL team considers this change likely applies to the whole of ACIS-S only (so far), but can only confirm an improvement in fitting of observation data for the LETG/ACIS-S configuration, with a 10mm sim-z offset, moving the LETG pattern nearer the ACIS-S chip readouts. (This reduces the CTI losses). This new file needs to be selected manually by the user, as indicated in the threads below: LETG/ACIS-S Grating ARFs: http://asc.harvard.edu/ciao/threads/mkgarf.letgacis.html#osip HETG/ACIS-S Grating ARFs: http://asc.harvard.edu/ciao/threads/mkgarf.hetgacis.html#osip (Optional use here) ACIS-S imaging (ACIS-S3, optional): Exposure Maps http://asc.harvard.edu/ciao/threads/expmap.single.html#createinstmap http://asc.harvard.edu/ciao/threads/expmap.multi.html#createinstmap ARFs with mkarf (ACIS-S3, optional) http://asc.harvard.edu/ciao/threads/psextract.thread.html#script http://asc.harvard.edu/ciao/threads/pieces.thread.html#ARF