The Table Access Protocol (TAP) web service allows the user to write SQL-like queries against the Chandra Observation Catalog using the Astronomical Data Query Language. The service implements the IVOA Table Access Protocol v1.0.

This TAP implementation supports both asynchronous and synchronous queries. The base URL for executing synchronous queries against the Chandra Observation Catalog TAP service is

https://cda.cfa.harvard.edu/cxctap/sync

The service accepts the following parameters in the HTTP query:

• REQUEST - Distinguish which service operation to execute. The value doQuery is required for ADQL queries.
• FORMAT - Result set output format. The following values are allowed:
  • votable - VOTable TABLEDATA serialization
  • text - Tab separated values
• LANG - Query language name. The value ADQL is required.
• PHASE - Query execution state. The value RUN is the default for the synchronous endpoint.
• QUERY - ADQL query.

A TAP request may be executed on the Unix command line using the HTTP query syntax with a command-line tool such as cURL or Wget.

curl --request POST \
  --location \
  --data REQUEST=doQuery \
  --data PHASE=RUN \
  --data FORMAT=votable \
  --data LANG=ADQL \
  --data 'QUERY=select o.obsid, o.ra, o.dec from cxc.observation o' \
  https://cda.cfa.harvard.edu/cxctap/sync

The /tables endpoint provides a complete listing of tables and columns available through the TAP web service.

An asynchronous endpoint is available for programmatic interfaces. We provide a graphical interface, seleste, which is built on top of the asynchronous functionality.

Finally, a form has been provided which will perform synchronous TAP queries.