The United States Naval Observatory (USNO) is a scientific and military facility that produces geopositioning, navigation and timekeeping data for the United States Navy and the United States Department of Defense. Established in 1830 as the Depot of Charts and Instruments, it is one of the oldest scientific agencies in the United States, and remains the country's leading authority for astronomical and timing data for all purposes.
The observatory is located in Northwest Washington, D.C. at the northwestern end of Embassy Row. It is among the few pre-20th century astronomical observatories located in an urban area; initially located in Foggy Bottom near the city's center, it was relocated to its Northwest DC location in 1893 to escape light pollution.
The USNO has conducted significant scientific studies throughout its history, including measuring the speed of light, observing solar eclipses, and discovering the moons of Mars. Its achievements including providing data for the first radio time signals, constructing some of the earliest and most accurate telescopes of their kind, and helping develop universal time. The Naval Observatory 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, the Naval Observatory campus hosts the official residence of the vice president of the United States.
History
Early presidential astronomical interest
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 the Secretary of the Navy officially adopted the latter.
Adams had made protracted efforts to bring astronomy to a national level. He spent many nights at the observatory, watching and charting the stars, which had always been one of his interests.
Establishment as an optical equipment depot
Established by 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.
Federal observatory
It was established as a national observatory in 1842 by federal law and a Congressional appropriation of $25,000. Lt. J.M. 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 other 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. It opened in 1844 in Foggy Bottom, north of the site of the Lincoln Memorial and west of the White House (see: Old Naval Observatory). The observatory moved to its Northwest DC location in 1893 located on a 2000 foot circle of land atop "Observatory Hill", overlooking Massachusetts Avenue.
The facilities were listed on the National Register of Historic Places in 2017.
The time ball
The first superintendent was Navy Commander M.F. Maury. Maury had the world's first vulcanized time ball, created to his specifications by Charles Goodyear for the U.S. Observatory. Placed into service in 1845, it was the first time ball in the United States and the 12th in the world. Maury kept accurate time by the stars and planets.
The time ball was dropped every day except Sunday, precisely at the astronomically defined moment of mean solar noon; this enabled all ships and civilians within sight to know the exact time. By the end of the American Civil War, the Observatory's clocks were linked via telegraph to ring the alarm bells in all of the Washington, D.C. firehouses three times a day.
The USNO held a one-off time-ball re-enactment for the year-2000 celebration.
The Nautical Almanac Office
In 1849 the Nautical Almanac Office (NAO) was established in Cambridge, Massachusetts as a separate organization. It was moved to Washington, D.C. in 1866, operating near Fort Myer. It relocated to the U.S. Naval Observatory grounds in 1893.
On 20 September 1894, the NAO became a "branch" of USNO; however, it remained autonomous for several years.