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 (PNT) for the United States Navy and the United States Department of Defense. 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 Air Force. The USNO performs radio VLBI-based positions of quasars with numerous global collaborators, in order to produce Earth Orientation parameters. Aside from its scientific mission, a house located within the Naval Observatory complex serves as the official residence of the Vice President of the United States. President John Quincy Adams, who in 1825 signed the bill for the creation of a national observatory just before leaving presidential office, had intended for it to be called the National Observatory. The names "National Observatory" and "Naval Observatory" were both used for 10 years, until a ruling was passed to officially use the latter. Adams had made protracted efforts to bring astronomy to a national level at that time. He spent many nights at the observatory, watching and charting the stars, which had always been one of Adams' avocations. Established by the order of the United States Secretary of the Navy John Branch on 6 December 1830 as the Depot of Charts and Instruments, the Observatory rose from humble beginnings. Placed under the command of Lieutenant Louis M. Goldsborough, with an annual budget of $330, its primary function was the restoration, repair, and rating of navigational instruments. It was made into a national observatory in 1842 via a federal law and a Congressional appropriation of $25,000. Lieutenant James Melville Gilliss was put in charge of "obtaining the instruments needed and books." Lt. Gilliss visited the principal observatories of Europe with the mission to purchase telescopes and scientific devices and books. The observatory's primary mission was to care for the United States Navy's marine chronometers, charts, and other navigational equipment. It calibrated ships' chronometers by timing the transit of stars across the meridian.