The Washington Double Star Catalog (WDS), maintained by the United States Naval Observatory (USNO), is the world's principal database of astrometric double and multiple star information. The WDS Catalog contains positions, discoverer designations, epochs, position angles, separations, magnitudes, spectral types, proper motions and when available, Durchmusterung numbers and notes for the components of close to 100,000 systems based on ~600,000 means. The current version at the HEASARC is updated weekly and is derived from the version available online at <a href="https://crf.usno.navy.mil/wds/">https://crf.usno.navy.mil/wds/</a>; (and mirrored at <a href="http://www.astro.gsu.edu/wds/">http://www.astro.gsu.edu/wds/</a>;), the latter being potentially updated nightly. The Washington Visual Double Star Catalog (WDS) is the successor to the Index Catalogue of Visual Double Stars, 1961.0 (IDS; Jeffers & van den Bos, 1963). Three earlier double star catalogs in the 20th century, those by Burnham (BDS; 1906), Innes (SDS; 1927), and Aitken (ADS; 1932), each covered only a portion of the sky. Both the IDS and the WDS cover the entire sky, and the WDS is intended to contain all known visual double stars for which at least one differential measure has been published. The WDS is continually updated as published data become available. Prior to this, two major updates have been published (Worley & Douglass 1984, 1997). The Washington Double Star Catalog (WDS) has seen numerous changes since the last major release of the catalog. The application of many techniques and considerable industry over the past few years has yielded unprecedented gains in both the number of systems and the number of measures. This version of the WDS catalog was first created at the HEASARC in March 2002 based on the USNO online version (available at either <a href="https://crf.usno.navy.mil/wds/">https://crf.usno.navy.mil/wds/</a>; or <a href="http://www.astro.gsu.edu/wds/">http://www.astro.gsu.edu/wds/</a>;), and is updated by the HEASARC on at least a weekly basis. The table schema was last revised in February 2005. This is a service provided by NASA HEASARC .
