Chandra X-Ray Observatory
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Last modified: 4 May 2017

URL: http://cxc.harvard.edu/caldb/index.html

Welcome to the
Chandra Calibration Database Website


The Chandra X-Ray Center has introduced version 4.7.4 of the Chandra Calibration Database (CALDB) on 04 MAY 2017.

See the CIAO Downloads page for instructions for an automated installation of CIAO 4.9 and CalDB 4.7.4 on your local system. Or for manual instructions, see the CalDB Downloads page to install or upgrade your Chandra CalDB to CalDB 4.7.4.

CalDB 4.7.4 includes the following updates:

  • ACIS T_GAIN Epoch 67+68
  • HRC-I QE version N0010
  • HRC-S BADPIX version N0004
  • HRC-S QEU version N0008
  • FILES RETIRED from the DISTRIBUTION

See details in the link CalDB 4.7.4 Release Notes.


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: 4 May 2017
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The Chandra X-Ray Center (CXC) is operated for NASA by the Smithsonian Astrophysical Observatory. 60 Garden Street, Cambridge, MA 02138 USA.   Email:   cxchelp@head.cfa.harvard.edu Smithsonian Institution, Copyright © 1998-2017. All rights reserved.