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Last modified: 16 June 2022


Welcome to the
Chandra Calibration Database Website

The Chandra X-Ray Center has introduced version 4.9.8 of the Chandra Calibration Database (CALDB) on 16 June 2022.

CalDB 4.9.8 has been released, for use in CIAO 4.14, and users are encouraged to download both using the Conda or ciao-install procedures.

See the CIAO web page for links to instructions using preferably Conda, or alternatively ciao-install, for an automated installation of CIAO 4.14 and CalDB 4.9.8 on your local system. Or for manual instructions, see the CalDB Downloads page to install or upgrade your Chandra CalDB to CalDB 4.9.8.


CalDB 4.9.8 is compatible with CIAO 4.12 and later versions ONLY! Please do not attempt to upgrade your CalDB for CIAO 4.11 or older versions with CalDB version 4.9.8. None of the ACIS upgrades in CalDB 4.9.8 will be applied with the older software because of required software changes to do so. Furthermore, the HRC-S chip edge offset values will not be applied in CIAO 4.11 with CalDB 4.9.8, and users will not be notified by the software if this occurs.

As a result of this, there will be no further CalDB upgrades provided for CIAO 4.11.

CalDB 4.9.8 includes the following updates:

See details in the links CalDB 4.9.8 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:

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.