The U.S. Naval Observatory: Mission, Products, and Services

The U.S. Naval Observatory: Mission, Products, and Services
Naval Observatory, USNO, astrometry, celestial reference frame, terrestrial reference frame, Earth Orientation Parameters, EOP, Very Long Baseline Interferometry, VLBI, proper motion, parallax, double star, star catalog, Astronomical Almanac, Nautical Almanac, Air Almanac, precise time, time scale, Coordinated Universal Time, UTC, UT1, Greenwich Mean Time, GMT, International Atomic Time, TAI, atomic clock