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 to produce positioning, navigation and timing for the United States Navy and the United States Department of Defense.
The observatory is located in Northwest Washington, D.C. at the northwestern end of Embassy Row. It is one of the pre-1900 astronomical observatories located in an urban area; at the time of its construction, it was far from the light pollution thrown off by the (then-smaller) city center.
Former USNO director Gernot M. R. Winkler initiated the “Master Clock” service that the USNO still operates, and which provides precise time to the GPS satellite constellation run by the United States Space Force. The USNO performs radio VLBI-based positions of quasars for astrometry and geodesy with numerous global collaborators (IERS), in order to produce Earth orientation parameters and to realize the celestial reference system (ICRF).
Aside from its scientific mission, a house located within the Naval Observatory campus serves as the official residence of the vice president of the United States.