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Last modified: 21 September 2015


Welcome to the
Chandra Calibration Database Website

The Chandra X-Ray Center has introduced version 4.6.9 of the Chandra Calibration Database (CALDB) on 23 SEP 2015.

The CalDB 4.6.9 upgrade is a patch upgrade to CalDB 4.6.5 and later versions. CIAO 4.7 nominally requires CalDB 4.6.5 or later version, due to a modification in acis_process_events GRADE file CalDB call, which is now modified for the DATA_MODE=CC33_GRADED case. However, CalDB 4.6.9 will work with CIAO version 4.5 and later, without the new event GRADE mapping for CC33_GRADED datamode ObsIDs.

See the CIAO Downloads page for instructions for an automated installation of CIAO 4.7 and CalDB 4.6.9 on your local system. Or for manual instructions, see the CalDB Downloads page to install or upgrade your Chandra CalDB to CalDB 4.6.9.

CalDB 4.6.9 includes the following updates:

  • ACIS T_GAIN Epoch 62 (May-Jul 2015) with Epoch 61 (Feb-Apr 2015) finalizations
  • ACIS-S1 Gain Table (DET_GAIN) upgrade
  • LETG/HRC-S LSF Parameter File (LSFPARM) upgrade, including improved Enclosed Energy Fractions (EEFRACs)
  • HRC-S Mean QE file update
  • HRC-I Mean QE file update
  • ACIS Group F (2009-09-21) BKGRND DTCOR Header Keyword fix

See details in the link CalDB 4.6.9 Release Notes.

PSFLIB hypercube files are now obsolete

With the advent of CIAO 4.5, the tool mkpsf is no longer supported or included. Hence, the ACIS and HRC PSFLIB hypercube files, nominally stored in ${CALDB}/data/chandra/{acis or hrc}/2d_psf, are obsolete. As previously promised, these files have now been removed from the CalDB distribution.

The CALDB is the directory and indexing structure that stores and provides access to all calibration files that are required for standard processing and analysis.

These files are used in standard data processing, as well as for analysis with software packages such as CIAO. When you apply a gain map, create an exposure map, or build response files (RMFs and ARFs) - among many other things - you are using the Chandra CALDB to apply the necessary calibration files.

The CALDB serves many functions:

  • Storing and archiving calibration files.

  • Maintaining a naming convention and header structure for all calibration files.

  • Indexing calibration data, based on FITS header keywords, for software access.

  • Permitting updates of calibration data independent of software updates, while maintaining configuration control.

  • Providing a traceable history of calibration data in the database by maintaining versioning.

  • Translating calibration products into formats suitable for processing and/or analysis.

These webpages contain information about each of these topics. They are also designed to help you (or your system manager) understand how the CALDB is assembled and how it works in the Chandra software system.

Please email the CXC Helpdesk with any questions or comments on the CALDB and this website.

Last modified: 21 September 2015
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