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Welcome to the
Chandra Calibration Database Website

The Chandra X-Ray Center has introduced version 4.12.4 of the Chandra Calibration Database (CALDB) on 23 April 2026.

CalDB 4.12.4 has been released for use in CIAO 4.18, and users are encouraged to download both using the Conda or ciao-install procedures.

See the CIAO web page for links to instructions using either Conda or ciao-install, for an automated installation of CIAO 4.18 and CalDB 4.12.4 on your local system. Or for manual instructions, see the CalDB Downloads page to install or upgrade your Chandra CalDB to CalDB 4.12.4.

CalDB 4.12.4 includes the following updates:

See details in the links CalDB 4.12.4 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.

Analysis Notes

Matching CIAO and CALDB Versions

CALDB 4.12.4 should not be used unless you are running CIAO 4.16 or later versions!

Are your versions mismatched? Time to upgrade CIAO and CALDB!

News

23 Apr 2026 [New]

CALDB 4.12.4 has been released to the public. Included in this release are (1) ACIS CONTAM File Library Reduction and (2) ACIS P2_RESP (mkacisrmf) input file lower FP_TEMP limit reduction. See the CalDB 4.12.4 Release Notes

18 Dec 2025

CfP Cycle 28 Release Includes CY28 PIMMS Effective areas information, ACIS and GRATING sample (G)RMFs and (G)ARFs for proposal planning by non-CIAO users.

16 Dec 2025

CALDB 4.12.3 has been released to the public. Included in this release are (1) ACIS CONTAM N0016 updates effective from 2021-11-01 through the present, (2) HRC-I QE file set upgrade version N0017, and (3) new PCAD DARK_CURR updates (four new files.) See the CalDB 4.12.3 Release Notes

19 Aug 2025

CALDB 4.12.2 has been released to the public. Included in this release are (1) ACIS T_GAIN updates effective from 2021-11-01 through the present, (2) HRC-S QEU file set upgrade version N0022, and (3) new PCAD DARK_CURR updates (three new files.) See the CalDB 4.12.2 Release Notes

31 Jan 2025

CalDB 4.12.0 has been released to the public. Included in this release are (1) new ACIS P2_RESP files for warm ACIS observations up to -105.0 C, and (2)the HRC-S QEU N0021 file set, See the CalDB 4.12.0 Release Notes

17 Dec 2024

CalDB 4.11.6 was released to the public. Included in this release are (1) the HRC-I QE N0016 file set, (2) PCAD ACA-P DARK_CURR file updates #9, and (3) Proposal Cycle 27 PIMMS Effective Areas. See the CalDB 4.11.6 Release Notes

16 Oct 2024

CalDB 4.11.5 was released to the public. Included in this release are HRC-S QE version N0017, and QEU version N0020 file sets as well as two new ACA-P DARK_CURR files (periodic updates #8), which do not affect CIAO. See the CalDB 4.11.5 Release Notes for details.

21 Aug 2024

CalDB 4.11.3 was released to the public. Included in this release is an updated HRC-S QEU time-dependent file set version 19 (34 new files), as well as four new ACA-P DARK_CURR files (periodic updates #7), which do not affect CIAO. See the CalDB 4.11.3 Release Notes for details.

06 Jun 2024

CalDB 4.11.2 was released to the public. Included in this release is an updated HRC-I QE time-dependent file set version 15 (38 new files). See the CalDB 4.11.2 Release Notes for details.

18 Apr 2024

CalDB 4.11.1 was released to the public. Included in this release are the new ACIS "warm-temperature" CTI corrections vN0012, and an updated HRC-S QEU N0018 file set (33 new files). Also included are set #6 of the PCAD ACA-primary DARK_CURR (dark current) image files. See the CalDB 4.11.1 Release Notes for details.

12 Dec 2023

CalDB 4.11.0 was released to the public. Included in this release are the new ACIS "warm-temperature" CTI corrections vN0011, and an updated HRC-I QE N0014 file set (37 new files). Also included are set #5 of the PCAD ACA-primary DARK_CURR (dark current) image files and the Cycle 26 PIMMS Effective Area configuration files, neither of which affect CIAO users. See the CalDB 4.11.0 Release Notes for details.

14 Sep 2023

CalDB 4.10.7 was released to the public. Included in this release are the latest HRC-S QE Uniformity data sets (version N0017) including one addtional data set effective for OBS_IDs taken after the HRC-S restart. Also included are more PCAD ACA-primary DARK_CURR (dark current) image files, which do not affect CIAO users. See the CalDB 4.10.7 Release Notes for details.

22 Mar 2023

CalDB 4.10.4 was released to the public. Included in this release are the latest ACIS T_GAIN (time-dependent gain) updates, which will be updated annually rather than semiannually going forward. Also included with this release are PCAD ACA-primary DARK_CURR (dark current) image files, which do not affect CIAO users. See the CalDB 4.10.4 Release Notes for details.