CALDB RELEASE NOTES Version: 2.26 (version 2 update 26) Effective Date: 2004-02-02T21:00:00 For Public Release by 17:00 EST 02-FEB-2004 I. SUMMARY OF CHANGES A. ACIS CONTAM Files Released The ACIS contamination files, versions 1-3, have been approved for release in the CALDB. Versions 1 and 2 are released for archival purposes, and contain the original model developed by H. Marshall of the HETGS team, published in the Summer of 2003. Version 3 contains the newest model, and is the ARDLIB default in this CALDB release, that is, it will be used by mkarf, mkwarf, mkinstmap, and mkgarf to correct for the time-dependent ACIS QE degradation measured from the date of the SSD opening. FILENAMES: acisD1999-08-13contamN0001.fits acisD1999-08-13contamN0002.fits acisD1999-08-13contamN0003.fits Location: $CALDB/data/chandra/acis/bcf/contam/ Affects: CIAO ARFs, GARFs, and exposure maps. B. -120C ACIS-S3 PHA FEFs corrected We discovered a remaining error in the S3 FEF response used in both the non-CTI and the CTI-corrected FEF files (S3 is not calibrated for CTI-correction at this point). This would produce a 1-channel shift when used with CIAO 3.0.2. The new S3 FEF is now free of the 1-channel shift in the RMF generated, regardless of energy range specified. FILENAMES: acisD2000-01-29fef_phaN0004.fits acisD2000-01-29fef_pha_ctiN0003.fits Location: $CALDB/data/chandra/acis/cpf/fefs/ Affects: CIAO mkrmf (ACIS-S3 (BI CHIP) responses) C. ACIS -110C OSIP files upgraded We have widened the acceptance regions in the -110C OSIP files, in particular for the BI chip ACIS-S1, which has the errors in the gain calibration, producing the broad wiggles in plots of grating orders versus wavelength across the array. FILNAMES: acisD1999-09-16osipN0006.fits acisD2000-08-11osipN0006.fits Location: $CALDB/data/chandra/acis/cpf/osip/ Affects: ACIS-S-Grating L1.5 pipeline (tg_resolve_events) D. NOTE: The modified QE_LETG file acisD1997-04-17qeN0004.fits, which was modified using a very early model of the time-dependent QE degradation, which was applied to the ACIS-S chips only, is no longer being distributed with the CALDB as of CALDB 2.26. This file was applicable only to a limited range of data, and is now upstaged by the CONTAM version N0003 model in "A" above. For those who have used the file in the past, it will not be deleted; however future versions of the CALDB will not include it now that the effect being addressed is better quantified. The file made no corrections to ACIS-I, and in future threads and releases, we would like to avoid any confusion therewith. The current ACIS default file, acisD1997-04-17qeN0003.fits, is the one required for use with any of the more recent time-dependent contamination correction routines. II. Technical Details A. ACIS CONTAM Files After some considerable effort, CXC is now able to release into the CALDB three files which model the contamination versus time of the ACIS optical path, which is the proposed explanation of the degradation of the ACIS QE with time. Three files are being released, two of them deprecated in the CALDB but released for archival purposes, and one of them version N0003, which is the new default ACIS CONTAM file in the ARDLIB. Versions N0001 and N0002 contain the original model derived by Herman Marshall and published in the SPIE paper available at the web page http://cxc.harvard.edu/cal/docs/figs/contam.ps entitled "Composition of the ACIS Contaminant." This model includes absorption edge features seen in grating spectra of various cosmic sources, which have been found to vary with time just as the ACIS-QE does. Version N0002 contains the same model, but with an added time point extending the effective date range of the file until the end of 2006. Version N0002 was used to build the Cycle 6 PIMMS and proposal planning ARFs for ACIS. Version 3 contains the new two-level or "fluffium" modeling developed by Dan Dewey of the HETGS team, and is described here: http://space.mit.edu/HETG/technotes/contam/twolevel.html. The new model includes consideration of the External Calibration Source (ECS) time-dependent modeling of the QE degradation, which was used originally to derive the ACISABS/corrarf correction model developed at Penn State. Hence the N0003 model is adjusted to give the flattening with time of the degradation seen in the ECS data. This model is now the recommended time-dependent correction to use with CIAO, and in fact in any analysis of Chandra data, according to the CXC. ACISABS and CONTAMARF, recommended until now, are now deprecated in favor of this model. NOTE: No spatial dependence is yet included in the CONTAM file. That is still a work in progress. Threads affected: "Correcting Responses for ACIS Contamination" http://cxc.harvard.edu/ciao/threads/aciscontam/index.html Includes recommendations for correction ARFs, GARFs, and Exposure Maps. B. ACIS-S3 -120C FEF correction As of CIAO 3.0.2, released 15 DEC 2003, there has been a fix of a software bug in mkrmf. The bug, which produced a one-channel shift in the RMF toward higher energies when the user specified a lower-bound energy that was below the lower limit of the S3 FEF (224.0 eV). From Kenny Glotfelty (CXCDS development team): ------------ "The bug report was that mkrmf produced different grids if the energy range the user supplied was below the minimum energy in FEF vs when the minimum energy was above the FEF grid. When the FEFs in the current release were generated for CALDB 2.7, 08 August 2001, the S3 FEF itself was derived inadvertently with this software error in tow, that is, with the shift being generated in the resultant RMF. Since then, a patch to CIAO 3.0 (version 3.0.2) has been released including the fix to the software. This release has exposed the procedural error in deriving the FEFs in the current release. We seek to correct this procedural error by releasing the corrected S3 FEF data forthwith, in both the CTI-corrected FEF file and in the non-CTI-corrected FEF file. (The FEF files contain FEF data for all 10 chips; S3 is not CTI-corrected at this point, and so the same S3 data go into each FEF table.) From Dick Edgar (ACIS CAL team): Subject: Re: "Description of Change" for FEF corrections From: "Richard J. Edgar" <edgar@head.cfa.harvard.edu> Date: Tue, 27 Jan 2004 11:47:32 -0500 "Up to ciao version 3.0.1, mkrmf had a bug which resulted in an off-by-one error in user-selected PHA channels when the user selected an energy scale which began at an energy lower than the lowest one in the FEF file. When creating the current (CALDB 2.7) S3 FEF, we inadvertently created RMFs for testing which contained this off-by-one error, and so adjusted the gains accordingly to make them fit the known energies of the Al, Ti, and Mn lines in the external calibration source, and oxygen and neon lines in E0102. This bug was fixed with ciao release 3.0.2, (15 Dec 2003). So to generate correct RMF files, the users will need a new S3 FEF file, which we are proposing to release. The centroids of all Gaussians representing lines have been shifted by the requisite number of channels, and validation against the external cal source and E0102 has been performed. The ACIS ad-hoc modeling committee recommends release of this product as soon as possible." NOTE: No change of gain file is necessary for these new FEFs. A simple shift of the channels of the Gaussian centroids was all that was necessary to correct the problem. Threads affected: "Extract ACIS Spectra for Pointlike Sources and Make RMFs and ARFs" http://cxc.harvard.edu/ciao3.0/threads/psextract/ "Step-by-Step Guide to Creating ACIS Spectra for Pointlike Sources: Calculate the RMFs" http://cxc.harvard.edu/ciao3.0/threads/pieces/index.html#rmf "Weighting ARFs and RMFs: multiple sources: Calculate the RMFs" http://cxc.harvard.edu/ciao3.0/threads/wresp_multiple_sources/index.html#wrmf C. ACIS -110C OSIP table We have known for some time that errors in the response function for CHIP ACIS-S1 (ACIS-5) have produced problems in the order-sorting of grating observations, because there appear to be wiggles in the orders as they appear in the S5 range in order-sorting wavelength-vs-TG order plots. We want to widen the acceptance region for ACIS-S1 for the -110C period of 1999-09-16 to 2000-01-29. From Dave H., 21 Jan 2004 memorandum: ftp://space.mit.edu/pub/cxc/Misc/OSIP_update_2004.01.21.ps.gz "I have reprocessed 13 Capella observations with HETG and ACIS-S to review order-sorting quality vs epoch imposed by the OSIP (order sorting and integrated probability) tables. One epoch, 1999-09-16 (ObsIDs 1103, 1318), requires an update because the CalDB OSIP file clips the -1 order for HEG on ACIS-S1. Data were processed with CIAO 3.0.2; no CTI correction was applied (nor is one available for the problem date). After seeing the problem, a few other observations were processed from the same epoch, and also showed the defect (ObsID:Object -- 16:AB Dor; 609: lambda And; 459: 3C273; 605: UX Ari)." [See the figures in the memo and the explanation of the effect.] Dave continues: "To amend the error, I have made a new OSIP file with a widened acceptance region for ACIS-S1..." The input files for the new OSIP are the same as for the old one; there is a notice included in the memo and in the Data Value Verification about the intervening upgrade of the -110C FEF, which is inconsequential to the response data, and to the OSIP. MKGARF uses the OSIP file's FRACRESP column to adjust the effective area vs. wavelength due to the admitance of the grating mask. (Hence not all diffracted photons are admitted into the PHA2 spectra, and the GARF must be appropriately adjusted.) From the file headers, the acceptance limiters and input files used: -- HISTORY CCD_IDs: 4, 5, 6, 7, 8, 9 -- HISTORY N_sigma_lo: -2.5, -7.0, -4.0, -3.5, -4.0, -2.5 -- HISTORY N_sigma_hi: 5.0, 5.0, 6.0, 5.0, 5.0, 2.5 -- HISTORY gain_file: acisD1999-09-16gainN0005.fits -- HISTORY fef_file: acisD1999-09-16fef_phaN0001.fits Threads affected: "Obtain Grating Spectra from (H/L)ETG/ACIS-S Data: Running tg_resolve_events" http://cxc.harvard.edu/ciao/threads/spectra_hetgacis/index.html#tg_resolve_events http://cxc.harvard.edu/ciao/threads/spectra_letgacis/index.html#tg_resolve_events (for -110C ACIS-S/grating observations only)