Chandra X-Ray Observatory

Replacement of bad target names

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  • The archive is fully functional.
Reprocessing Status
    Reprocessing IV has been completed in December 2014.
Current Software Releases
  • ASCDSVER: 10.11.1
  • CALDBVER: 4.10.2
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
Bad target names replacement project

Good Target Names

In order to improve searchability and general utility of the Chandra archive, we are asking that observers double-check that their target names carry sufficient information to unequivocally identify the astronomical source or area of the sky observed and follow IAU specifications. With the exception of TOO observations where the target is not yet known, observers should therefore:  

Check that the target name is recognized as a unique source by at least one of the following:


If the target name is not recognized by either of the services above, the next step is to check if there is an existing "resolvable" name, i.e., one that corresponds unambiguously to a unique set of sky coordinates and that can be "resolved" into these coordinates, following these guidelines:

  • Please do not use underscores "_" in your target name. Instead, use blanks " " or no space.
  • If your target is spatially associated with, contained in, superimposed on, or part of an extended/diffuse astronomical source with a resolvable designation (for example, a stellar source in a globular cluster or galaxy with a resolvable target name), please prepend the resolvable name of the "parent" object to your target name, e.g., "M31 BHXN", where BHXN stands for Black Hole X-ray Nova.
  • When available, use a catalog identifier (or a reference for the paper containing the catalog), or more generally any useful "subcomponent" of the designation as defined at in the target name.
  • Check that the field coordinates part is correct and carries enough spatial resolution (see

Sometimes, no practical resolvable name will be available, but a suitably informative name can be assigned. Such cases may include:

  • Composite target names, which do not resolve as a whole but contain resolvable substrings, e.g., "Abell1882 - Filament #1"
  • Surveys, deep fields, etc. that have no single "center" or "location" attached to them
  • Transients, variable sources, or EM counterparts of multi-messenger events. Their designations do not usually follow IAU specifications and are not immediately resolvable (e.g.,, "GW170817" was not resolvable for more than 1 year after detection) but they are distinguishable and clear.

Observers can also check if the target was observed in the past but with a different name in the Chandra Archive by using ChaSeR, and may consider using that name.    

For additional help, please contact  
See here for more information on the Chandra Archive Operations team's work on this subject.

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Last modified: 2020-10-29

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