United States Naval Observatory

The United States Naval Observatory (USNO) is one of the oldest scientific agencies in the United States, with a primary mission[1] to produce Positioning, Navigation, and Timing (PNT)[2] for the U.S. Navy and the U.S. Department of Defense. Located in Northwest Washington, D.C., it is one of the few astronomical observatories located in an urban area; at the time of its construction, it was far from the light pollution generated by the (then-smaller) city center. Today, the observatory's primary observational work is done at the U.S. Navy's higher elevation United States Naval Observatory, Flagstaff Station (NOFS) near Flagstaff, Arizona. USNO also has an "Alternate Master Clock" site in Colorado Springs, CO,[3] which with the "Master Clock",[4] provides precise time to the GPS satellite constellation run by the U.S. Air Force; and it performs radio VLBI-based positions of quasars with numerous global collaborators, in order to produce Earth Orientation parameters. Aside from its scientific mission, since 1974, the Observatory is the official residence of the Vice President of the United States.

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