PUBLIC RELEASE NOTES CalDB Version 3.2.0 CalDB Effective Date: 16 Nov 2005 NOON EST For Public as well as SDP release; Public release at 2005-11-21T12:00:00 I. Introduction CalDB 3.2.0 includes upgrades to the ACIS -120C responses suite which includes CTI, T_GAIN, DET_GAIN, and P2_RESP updates, a correction to the -120C ACIS BADPIX input files, HRC-I gain maps, and an upgrade to HRC-S GAPLOOKUP table. All of the above files except ACIS P2_RESP will be used in "Repro 3" the next round of archival reprocessing of all Chandra observations, expected to begin before January 2006. These items have been installed in current SDP as of Tuesday 15 Nov 2005, with the installation of DS 7.6.4. II. Summary of Changes A. ACIS -120C BADPIX corrections Location: $CALDB/data/chandra/acis/bcf/badpix/ Filenames: acisD2000-01-29badpixN0003.fits acisD2000-07-04badpixN0003.fits acisD2000-07-06badpixN0003.fits acisD2000-08-12badpixN0003.fits acisD2000-11-28badpixN0003.fits A correction has been made to change the STATUS bits on the six node boundary columns for all ten chips in these files. This will reduce the number of events excluded due to proximity to the node boundary, because these will be treated differently than ordinary bad pixels. Pipes/Tools: SDP only. ACIS L1: acis_build_badpix Threads affected: NONE B. ACIS -120C responses suite version 5 (CTI, T_GAIN, GAIN, P2_RESP) 1. -120C ACIS FI chip CTI correction files: Location: $CALDB/data/chandra/acis/bcf/cti/ Filenames: acisD2000-01-29ctiN0005.fits acisD2002-08-01ctiN0005.fits We are attempting to account for some known degradation in the ACIS CTI with time, in particular for some broadening of the main peak in the ACIS response, by using two sets of trap density maps in the CalDB, one set used for January 29, 2000- August 01, 2002, and the next set for August 1 2002 through the present epoch. 2. -120C T_GAIN correction files: Location: $CALDB/data/chandra/acis/bcf/t_gain/ Filenames: acisD2000-01-29t_gainN0005.fits acisD2000-05-01t_gainN0005.fits acisD2000-08-01t_gainN0005.fits acisD2000-11-01t_gainN0005.fits acisD2001-02-01t_gainN0005.fits acisD2001-05-01t_gainN0005.fits acisD2001-08-01t_gainN0005.fits acisD2001-11-01t_gainN0005.fits acisD2002-02-01t_gainN0005.fits acisD2002-05-01t_gainN0005.fits acisD2002-08-01t_gainN0005.fits acisD2002-11-01t_gainN0005.fits acisD2003-02-01t_gainN0005.fits acisD2003-05-01t_gainN0005.fits acisD2003-08-01t_gainN0005.fits acisD2003-10-19t_gainN0005.fits acisD2003-11-18t_gainN0005.fits acisD2004-01-01t_gainN0005.fits acisD2004-02-01t_gainN0005.fits acisD2004-05-01t_gainN0005.fits acisD2004-08-01t_gainN0005.fits acisD2004-11-01t_gainN0005.fits acisD2005-02-01t_gainN0005.fits acisD2005-05-01t_gainN0002.fits The new T_GAIN files have higher density spatial mapping than previous editions. This is to address the apparent gain sag noticed in the N0004 suite processing, within +/-50 columns from Column 512 of the FI chips. Note: The previous T_GAIN datasets (versions N0003 and N0004) have been removed from the CalDB distribution as of 3.2.0, to reduce the size of the tar balls. Users who do not delete these files from their own CalDB installations will still have them. However, they are marked OFFLINE in the new index. 3. ACIS -120C DET_GAIN N0005 for CTI corrected FI chips (BI uncorrected) Location: $CALDB/data/chandra/acis/bcf/gain/ Filename: acisD2000-01-29gain_ctiN0005.fits The new DET_GAIN file has the same data as N0004 except for the S2 (ACIS-6) FI chip, which has been modified for the NEW CTI and RMF inputs also released with the N0005 suite. It will be the default gain file in ALL ACIS processing from 16 Nov 2005 forward, and from the initiation of live processing with DS 7.6.4 forward. 4. ACIS Phase 2 (P2_RESP) N0005 response inputs for CIAO "mkacisrmf" Location: $CALDB/data/chandra/acis/cpf/p2_resp/ Filename: acisD2000-01-29p2_respN0005.fits Upgrades have been made to the BI chip PRE_CTI response matrix inputs. (SEE Block 3 of this file.) This incorporates the ACIS SI team's new model for the low-energy tail of the RMF. The results do not change the apparent gain of these chips, but should markedly improve some fitting results for S1 and S3. In addition, due to the upgrade in the ACIS-S2 (ACIS-6) CTI corrections in the N0005 suite, the CTI-induced scatter contribution (See block 4 of this file) has been modified from version N0004. Hence this file must only be used to analyzed ACIS-6 results that have been reprocessed with the ACIS N0005 suite applied within "acis_process_events." For the other seven FI chips, this file will give the same responses as p2_resp N0004. Pipes/Tools affected (by items B.1-4): ACIS L1 processing (acis_process_events) CIAO acis_process_events CIAO mkacisrmf Threads affected by the ACIS N0005 Suite: "Apply the ACIS CTI Correction" http://cxc.harvard.edu/ciao/threads/acisapplycti/ "Apply the Time-Dependent ACIS Gain Correction" http://cxc.harvard.edu/ciao/threads/acistimegain/ "Creating ACIS RMFs with mkacisrmf" http://cxc.harvard.edu/ciao/threads/mkacisrmf/ 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/ CAVEAT RE the ACIS N0005 Responses Suite: http://cxc.harvard.edu/calco/caveats/acis_caveat_N0005.html C. HRC-I GMAPs N0001 (gain maps) Location: $CALDB/data/chandra/hrc/bcf/gain/ Filenames: hrciD1998-10-30gainN0001.fits hrciD1999-10-04gainN0001.fits For the first time, there will be GMAPs applied to HRC-I data in standard data processing, with the installation of these two GMAP correction images in the CalDB. Two maps are needed because there has been a change in the HRC-I MCP High Voltage setting as of the date of the second file, which adjusts the gain somewhat. Pipes/Tools affected: CIAO and SDP "hrc_process_events" The tool automatically runs the PHA-to-PI conversion if an HRC-I gainmap is present in the CalDB. NO action required by user except to run the tool. Threads affected: "Create a new (HRC) L2 Events file" http://cxc.harvard.edu/ciao/threads/createL2/index.html#hrc D. HRC-S GAPLOOKUP N0002 Location: $CALDB/data/chandra/hrc/bcf/gaplookup/ Filename: hrcsD1999-07-22gaplookupN0002.fits This file is the first iteration of corrections for the known non-linearity in the HRC-S/LETG spatial wavelength scale that has been frequently alluded to in the literature. A second correction (N0003) will be released in the not-too-distant future. This first iteration will improve the performance of the LETGS significantly, but does not account fully for all the systematic errors in the dispersion relation. Pipes/Tools affected: HRC L1 processing (hrc_process_events) in DS 7.6.2 (TBD release date) CIAO hrc_process_events (CIAO 3.2.2 patch and later versions) Threads affected: HRC-S Degap Correction http://cxc-test.harvard.edu/ciao/threads/hrcs_degap/ III. Technical Details A. ACIS -120C BADPIX version N0003 A problem has been discovered with the N0002 versions of these files, which were released with CalDB 3.0.2 in Feb. of 2005. The node boundary columns (256-257, 512-513, and 768-769) had been marked not only as node boundaries (STATUS bit 12 set), but also as regular bad pixels (STATUS bit 1 set). This protocol has been changed in version N0003 files. Now the status bit 1 is no longer set for node boundary columns UNLESS they have been identified as being hot columns independently. B. ACIS -120C Responses (CTI, T_GAIN, DET_GAIN, and P2_RESP) N0005 1. CTI corrections N0005 (for FI chips only at this point) It has been known for some time that the increasing CTI effect with time is degrading the ACIS FI chip responses, both in main peak position (corrected by T_GAIN) and in FWHM. It has been decided that we will deal with the FWHM degradation by occasionally updating the trap density maps that are used in the CTI-correction algorithm of acis_process_events. To that end, two time-displaced CTI files are being added to the CalDB in this release. The first has trap density maps derived from External Calibration Source data taken during 29 January 2000 through 31 January 2001. This corresponds to T_GAIN epochs 1-4. These TDMs are all the same as in the N0004 CTI file from CalDB 3.1.0, except for chip ACIS-S2 (ACIS-6). A new S2 trap map was derived using "alpha" and "f" values taken from derivations using ECS data from T_GAIN epochs 18-21. This first CTI file will be applied to data taken over TT=2000-01-29T20:00:00 to TT=2002-08-01T00:00:00, or T_GAIN epochs 1-10. The second CTI file was built from trap density maps derived from ECS data over T_GAIN epochs 18-21, which corresponds to January 1-Oct 31 2004. Several of these TDM's needed bad column substitutions in their compilations. These TDM's will be applied, rather than the first set above, for dates after TT=2002-08-01T00:00:00, which corresponds to T_GAIN epoch 11-present. 2. ACIS T_GAIN N0005, epochs 1-23, epoch 24 preliminary N0002 CXC Calibration Scientist Alexey Vikhlinin has produced new T_GAIN correction CIP files which are named corrgain.v4.fits, as part of the generation of upgraded responses for ACIS in CTI-corrected mode for FI chips, and in not-corrected mode for S1 and S3, the BI chips. These files have been compiled into the standard interpolation pairs that compose the CalDB T_GAIN files. It has been found that a significant droop in gains in the central columns of most of the FI chips with our best RMF calibrations. This particular effect increases with photon energy, and becomes unacceptably large in the 4-5 keV range (as indicated by results using ECS lines.) This effect can be alleviated by using a higher-spatial resolution T_GAIN correction for those chips (I0, I1, I2, I3, and I6). The new T_GAIN N0005 files have this enhancement for these chips. Hence for these chips, there are now 1024, rather than 128, t-gain correction regions defined. This considerably increases the size of the datasets. Furthermore, if any users' data and fitted results are sensitive to this central column gain droop at high energies, they are well-advised to reprocess these data using the new T_GAIN files, as this is the only way to remove or mitigate this effect in the DS or CIAO software. 3. ACIS -120C DET_GAIN N0005 for CTI-corrected FI chips, uncorrected BI chips. The only change here is due to the upgrade/correction of the CTI trap density map for ACIS-S2 (ACIS-6). All other values in the file are the same as for N0004. 4. ACIS -120C P2_RESP N0005 (inputs for mkacisrmf) Changes have been made to the S2 epoch 1-4 trap density map in order to improve epoch 1 gain residuals. Hence there is an update to the scattering matrix for chip S2 in the P2_RESP data file. (This is a portion of Block 4 of the P2_RESP file) Additionally, we have long been aware of the need for an improved model for the low-energy tails of the BI chip responses. G.Y. Prigozhin has provided this new model, which results in new PRE_CTI_MATRIX data for S1 and S3 (see block 3 of the P2_RESP file). All other values are the same in the new P2_RESP file as they have been in the released version, N0004, which went public in June 2005. Hence, users who process their data with the new trap density maps and T_GAINS (or receive original processing or archived Repro 3 data with same) will NEED to use the new P2_RESP file N0005 in their analysis. There remains a residual effect on the central nodes of the FI chips, more striking on some than on others. C. HRC-I GMAPs version N0001 The HRC calibration team has produced two gain map (GMAP) files to be used to populate the PI column of the output L1 and L2 events files. This will initiate the PI calculations for the HRC-I in standard processing, as this has not been installed in the CalDB before at all. The original gain map, derived from laboratory sources only, applies to the first portion of the mission, before the voltage adjustment of 1999-10-04. A second gain map applies to all data taken since that date, and was derived from this original data plus flight observations. Illustrations of the GMAPs are available at the Cal Web page. http://cxc.harvard.edu/cal/Hrc/gain.html#maps Shown below is the version 1 gain correction map for the HRC-I (Oct 2005 by C. Wilton, J. Posson-Brown, and V. Kashyap), based on lab and flight data. To make this map, we used lab flats at six energies to get median values of the gain, and constructed an average gain map using these separate maps. This gain map was then modified to match the on-axis PHA profile of AR Lac, using a raster of off-axis AR Lac observations carried out at the current flight voltage setting. In standard data processing, this map provides multiplicative gain correction factors as a function of location on the detector. These values are used to convert pulse height amplitude (PHA) values to pulse invariant (PI) values. The respective FITS files are http://cxc.harvard.edu/cal/Hrc/Documents/hrci_gain_corr_v0.fits and http://cxc.harvard.edu/cal/Hrc/Documents/hrci_gain_corr_v1.fits These have been copied to the new CalDB filenames in the "description of change" section. The procedures used in deriving the gain maps are described in some detail in the Chandra Calibration Workshop (2005) poster "The HRC-I Gain Map" http://cxc.harvard.edu/ccw/proceedings/05_proc/presentations/wilton/. An HRC-I (PI) RMF has been generated, for use in deriving fluxes using Sherpa or Xspec (or similar fitting environment) to allow flux calculations from modeled spectra; It will be released at a later date. D. HRC-S GAPLOOKUP N0002 It has long been realized that the LETGS spatial grating pattern has a certain small-scale nonlinearity in the relation between wavelength and position along the three HRC-S plates. This nonlinearity is related to the degap procedure, and the corrections thereof have been deferred until solutions could be developed. A great source for the description of the problem for LETGS is the SPIE 2004 LETGS paper: Update on the Non-Linearities in the Chandra LETG/HRC-S Dispersion Relation, http://cxc.harvard.edu/cal/spie/letg_2004.ps We have here the first iteration (of an anticipated two iterations) of the wavelength scale correction via a new GAPLOOKUP table, the subject HRC-S N0002 GAPLOOKUP file for the CalDB. Basic technical details are described on the HRC calibration web page at http://cxc.harvard.edu/cal/Letg/Hrc_disp/degap.html#intro >From this source: "The degapping algorithm currently used for Chandra data analysis was derived by fitting symmetric 5th-order polynomials around tap center, to lab data. It still has some defects, such as a 1-pixel drop-off between taps, invalid corrections due to the assumed symmetry of the degapping, etc. These errors contribute to the observed non-linearities in the LETGS+HRC-S dispersion relation. The HRC-S poses some unique practical difficulties in the determination of degapping solutions using on-orbit data. Due to an uncorrectable error in the onboard electronics, the anticoincidence counter has been turned ineffective, and the telemetered data contain a large number of particle events, which strongly affects the pattern of the amplifier signals, and adversely affects the degapping solution. These background events are reduced, but never entirely eliminated, using various filtering steps during analysis. Therefore, degapping solutions are strongly tied to the filtering applied to the data. Further, the analysis naturally depends on photons dispersed by the LETGS, whose numbers depend on the shape of the source spectrum and the telescope effective area, and hence there are less data available on the outer plates. It is imperative that the true distribution of the photons across a tap be known exactly, or else the degap solution will be subject to large systematic errors. We have derived corrections to the wavelength scale based on analysis of sources with strong line emission (Chung et al. 2005). This was first made available via a Perl script corrlam and has now been incorporated directly into the degap solution (Kashyap et al. 2005). The new degap, which is the polynomial solution modified by corrections derived from line-emission data, is available from CALDB 3.2.0 onwards in the file $CALDB/data/chandra/hrc/bcf/gaplookup/hrcsD1999-07-22gaplookupN0002.fits This solution improves the performance of the LETGS significantly, but does not account fully for all the systematic errors in the dispersion relation. The rms deviation of the wavelength differences drop from 0.014 Å (0.010 Å over just the central plate) prior to the correction, to 0.010 Å (0.006 Å over the central plate)." A detailed description of the new degap solution is available from the SPIE paper of 2004, Chandra HRC-S Degapping Corrections http://cxc.harvard.edu/cal/spie/spie_degap.ps And an update to this has been presented at the 2005 Chandra Calibration Workshop, and will be posted under http://cxc.harvard.edu/ccw/proceedings/05_proc/presentations.