USNO and Paris Observatory jointly operate the International Earth Rotations and Reference System (IERS) International Celestial Reference System (ICRS) Product Center (IERS ICRS Center). The IERS ICRS Center is responsible for the maintenance of the International Celestial Reference System (ICRS) and the International Celestial Reference Frame (ICRF). Membership on the IERS Directing Board rotates between the USNO and the OP lead every three years. Responsibilities of the IERS ICRS Center include maintaining and disseminating the ICRS and associated data products and information, performing specific analyses on a regular basis and providing these products to the IERS, astronomical and geodetic communities, and generating an annual report describing the preceding year’s work, which is available in the IERS Annual Report.

Below you will find a list of current IERS standard products and links to the IERS and Paris Observatory. For more information on what the ICRS and ICRF are, click here.



  • USNO Bright Star Catalog: USNO Bright Star Catalog (UBSC) is a new astrometric catalog of 1423 brightest stars covering the entire sky. Details can be found in the corresponding manuscript by Zacharias et al. published in The Astronomical Journal.
  • USNO VLBI Spectroscopic Catalog: Value-added catalog of over 1000 ICRF3 objects with available SDSS/BOSS spectroscopy, fitted using the Bayesian AGN Decomposition Analysis for SDSS Spectra software. Details of the analysis, as well as column descriptions, can be found in the corresponding manuscript by Sexton et al. (2022) published in The Astrophysical Journal Supplement.
  • The GNC v1.1 Star Catalog: The Guidance, Navigation & Control (GNC) standard reference star catalog is produced by USNO to fulfill the need for a multi-purpose bright star catalog, with a limiting magnitude of Gaia G < 11 mag. This full-sky catalog provides the astrometric parameters and optical and near-infrared magnitudes for 1.2 million stars. Additional data, such as variability and multiplicity flags, distance to nearest stellar neighbor, and photocentric shift are also given. Details of the catalog, as well as column descriptions, can be found in the corresponding documentation.