Chandra X-Ray Observatory

Digital Object Identifiers

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CDA Status
  • The archive is fully functional.
Reprocessing Status
    Reprocessing IV has been completed in December 2014.
Current Software Releases
  • ASCDSVER: 10.12.6
  • CALDBVER: 4.11.1
What's New
  • Electrical Outage 11/05/21 - 11/06/21
    There will be a planned electrical outage Friday, November 5 2021, 5:30PM - Saturday, November 6 2021, 6:00PM EDT. During this time period ChaSeR and other archive interfaces will be unavailable.
  • Electrical Outage on 07/28/21
    There will be a planned electrical outage Wednesday, July 28 2021, 8:00PM - 10:00PM EDT. During this time period ChaSeR and other archive interfaces will be unavailable.
  • Downtime on 6/12/21
    Due to electrical work, the public interfaces of the Chandra Data Archive will not be available on Saturday 6/12 from 4 AM to 9 PM.
  • Repro V Begins
    The fifth major reprocessing of the archive (Repro V) has started! Details can be found here.
  • Past Notices
Digital Object Identifiers

Digital Object Identifiers for the Chandra archive


Citing Chandra observations in the literature allows archive users immediate access to the papers published on particular (sets of) observations, and readers equally immediate access to the Chandra data used in a particular paper. Comprehensive linking between data and publications has enabled the Chandra Data Archive (CDA) to derive meaningful metrics on the use of Chandra observations in scientific and technical literature, and quantitatively demonstrate the continued and sustained scientific impact of the mission.


DOIs as Chandra data identifiers

DataCite Digital Object Identifiers (DOIs) have replaced the previously used dataset identifiers to provide a more versatile and powerful mechanism for fast, efficient and durable access, citation and cross-linking of Chandra observations in the scientific literature.

The identifiers of observations taken after March 24 2020 are native DOIs, while for all observations taken prior to March 24 2020, newly minted DOIs have replaced the old persistent identifiers during Repro V. The Chandra DOIs populate the DS_IDENT keyword located in the headers of all FITS data products that can be unequivocally associated with a single Chandra Observation Identifier (ObsID). For example, the DOI of ObsID 23336 is defined as: "10.25574/23336" where the prefix "10.25574" identifies the CDA. The "landing page" for all archival Chandra DOIs, where the Chandra observation is linked and can be retrieved from, can be generated by prepending the fixed fragment "" to the specific DOI, as in:


DOI usage

The main goal of DOI adoption is to ensure that Chandra data used in publications can be easily found and retrieved, and we encourage all users to include DOIs in their scientific publications by requesting the creation of a Chandra Data Collection (CDC) DOIs.


Chandra DOI metadata

The DOIs minted for all Chandra data products follow the DataCite v4.1 metadata schema. Chandra DOIs are enhanced with a basic set of metadata that can be used to search and retrieve Chandra observations through DOI-based search engines (for example this), and reconstruct the data-literature linkages.

Two classes of metadata can be distinguished:

  • Observational metadata: based on properties of the observations, these metadata are assigned when data are processed and updated (if applicable) when data are reprocessed and/or when the observation becomes public.
  • Bibliographic metadata: based on the data linkage to literature, these metadata are assigned and updated when an observation is used in a publication included in the CDA bibliography.

The definitions of all metadata associated with the Chandra observations DOIs are available here.

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Last modified: 2020-09-25

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