CALDB PUBLIC RELEASE NOTES Version: 2.3 CALDB DATE: 2001-03-07T14:50:00 (Noon EST) Release notes are available for viewing at http://cxc.harvard.edu/caldb/version_release_notes.html CALDB 2.3 is required for running CAIO 2.1 and higher versions successfully. See the CALDB download page to acquire CALDB 2.3 or an upgrade from an early Chandra CALDB release. http://cxc.harvard.edu/caldb/download.html. I. SUMMARY of CHANGES A. A new PIXLIB-type file which includes the grating SHELL GEOMETRY, that is the grating SHELL diameters, which have until now been kept as parameter in the file "grating.par". CIAO 2.1 will use the new SGEOM file for these default values. The change is data-neutral. CIAO 2.0+ and ASCDS U5UPD14.3 is unaffected. U6 WILL use this new file instead of grating.par. FILENAME: $CALDB/data/chandra/tel/bcf/geom/telD1999-07-23sgeomN0001.fits B. LETG clocking angle reset to 0.0 degrees (from 0.0160 degrees), in the UPDATED GEOM PIXLIB file. This produces very little affect, if any. FILENAME: $CALDB/data/chandra/tel/bcf/geom/telD1999-07-23geomN0003.fits C. NEW LETG/HRC-S PI region filter files for three half-width factors, giving different levels of background filtering for LETG/HRC-S in PI space. These can reduce background by a factor of two or more. See the CIAO 2.1 threads page upon release of CIAO 2.1, expected today. FILENAMES: $CALDB/data/chandra/hrc/bcf/tgmask2/letgD1999-07-22pireg046_N0001.fits $CALDB/data/chandra/hrc/bcf/tgmask2/letgD1999-07-22pireg062_N0001.fits $CALDB/data/chandra/hrc/bcf/tgmask2/letgD1999-07-22pireg075_N0001.fits II. TECHNICAL DETAILS A. The SGEOM file is a data-neutral change which loads the four grating diameter values into the CALDB, instead of more or less hiding them in a parameter file. NO AFFECT ON YOUR DATA. B. The GEOM file update only changes the LETG clocking angle, and very slightly at that. Flight data analysis reveals that the correct value is actually zero degrees, as per design, rather than 0.0160 degrees, as per ground assembly estimate. CIAO 2.0.2 and 2.1 will use the value immediately. Standard Data Processing will NOT USE THIS NEW VALUE in Level 1.5 grating processing until R4CU6 (emphasize "U6") is installed, expected by March 29, 2001. The affect is miniscule. C. These PI region filter files are USER-SPECIFIED files. The LETG/HRC-S background filtration thread on the CIAO (2.1) threads page explains how to use them. See also the LETGS CAL USER page entry, at http://asc.harvard.edu/cal/Links/Letg/User/Hrc_bg/ which gives more calibration details, and refers you to the specific CIAO web page, when timely.