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Last modified: 27 August 2014


Welcome to the
Chandra Calibration Database Website

CAVEAT POSTED regarding HRC-S QE Uniformity file search errors

NOTE: The problems reported on this caveat page have been mitigated with the release of CalDB version 4.6.3 on 29 August 2014. Upgrade to that version to eliminate these issues.

As of 25 July 2014: We have discovered HRC-S QEU file search errors for Obs_IDs from 1999 and from 2014, wherein the wrong file is delivered from CalDB. Details and a workaround are available at this link.

The Chandra X-Ray Center has introduced version 4.6.3 of the Chandra Calibration Database (CALDB) on 29 AUG 2014.

The CalDB 4.6.3 upgrade is a patch upgrade to CalDB 4.5.9 and later versions. CalDB 4.6.3 nominally requires CIAO 4.5 or later version, due to the recent upgrade in the caldb4 software in CIAO 4.5, which allows CalDB files with overlapping validity date ranges to be selected properly.

See the CIAO Downloads page for instructions for an automated installation of CIAO 4.6.1 and CalDB 4.6.3 on your local system. Or for manual instructions, see the CalDB Downloads page to install or upgrade your Chandra CalDB to CalDB 4.6.3.

CalDB 4.6.3 includes the following update:

  • ACIS T_GAIN Epoch 58 (May-Jul 2014)
  • HRC-S Time-Dependent QEUs for 2014-2020
  • Retiring old HRC-S QEU files
  • Changes to HRC-I 2006 GMAP Validity Dates

See details in the link CalDB 4.6.3 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: 27 August 2014
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