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.[2] Established in 1830 as the Depot of Charts and Instruments, it is one of the oldest scientific agencies in the United States,[3] and remains the country's leading facility for astronomical and timing data.[4]
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. In 1893, in an effort to escape light pollution, it was relocated from Foggy Bottom near the city's center, to its Northwest Washington, D.C. location.
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.[5] 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.[4] 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, since the 1970s the Naval Observatory campus hosts 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.[6]
The names "National Observatory" and "Naval Observatory" were both used for 10 years, until the Secretary of the Navy officially adopted the latter.[7]
Adams had made protracted efforts to bring astronomy to a national level.[8][9] He spent many nights at the observatory, watching and charting the stars, which had always been one of his interests.
Established by order of the United States Secretary of the Navy John Branch on 6 December 1830 as the Depot of Charts and Instruments,[10] 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 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."[11] Lt. Gilliss visited the principal observatories of Europe with the mission to purchase telescopes and other scientific devices, and books.[12]
La misión principal del observatorio era cuidar los cronómetros marinos , cartas y otros equipos de navegación de la Armada de los Estados Unidos . Calibró los cronómetros de los barcos cronometrando el tránsito de las estrellas a través del meridiano . Se inauguró en 1844 en Foggy Bottom , al norte del sitio del Monumento a Lincoln y al oeste de la Casa Blanca .
En 1893, el observatorio se trasladó a su ubicación actual en el noroeste de Washington, DC [13] ubicado en un círculo de terreno de 2000 pies en la cima de "Observatory Hill", con vista a la Avenida Massachusetts .
En 2017, las instalaciones fueron incluidas en el Registro Nacional de Lugares Históricos . [14]
El primer superintendente fue el comandante de la Armada MF Maury . Maury tuvo la primera bola de tiempo vulcanizada del mundo , creada según sus especificaciones por Charles Goodyear para el Observatorio de Estados Unidos. Puesto en servicio en 1845, fue el primer balón en los Estados Unidos y el duodécimo en el mundo. Maury mantuvo la hora exacta de las estrellas y los planetas.
La bola del tiempo se dejaba caer todos los días excepto el domingo, precisamente en el momento astronómicamente definido del mediodía solar medio ; esto permitió que todos los barcos y civiles a la vista supieran la hora exacta. Al final de la Guerra Civil estadounidense, los relojes del Observatorio estaban conectados vía telégrafo para hacer sonar las alarmas en todas las estaciones de bomberos de Washington, DC tres veces al día.
La USNO celebró una recreación única de un balón de tiempo para la celebración del año 2000. [15]
En 1849, la Oficina del Almanaque Náutico (NAO) se estableció en Cambridge, Massachusetts, como una organización separada. En 1866, se trasladó a Washington, DC , operando cerca de Fort Myer. Se trasladó a los terrenos del Observatorio Naval de EE. UU. en 1893. [16]
El 20 de septiembre de 1894, la NAO se convirtió en una "sucursal" de la USNO; sin embargo, permaneció autónomo durante varios años. [dieciséis]
El sitio alberga la biblioteca de astronomía más grande de los Estados Unidos (y la colección de publicaciones periódicas astrofísicas más grande del mundo). [17] La biblioteca incluye una gran colección de libros raros de física y astronomía del último milenio.
An early scientific duty assigned to the Observatory was the U.S. contribution to the definition of the Astronomical Unit, or the AU, which defines a standard mean distance between the Sun and the Earth. This was conducted under the auspices of the congressionally-funded U.S. Transit of Venus Commission. The astronomical measurements taken of the transit of Venus by a number of countries since 1639 resulted in a progressively more accurate definition of the AU.
Relying strongly on photographic methods, the naval observers returned 350 photographic plates in 1874, and 1,380 measurable plates in 1882. The results of the surveys conducted simultaneously from several locations around the world (for each of the two transits) produced a final value of the solar parallax, after adjustments, of 8.809″, with a probable error of 0.0059″, yielding a U.S.-determined Earth-Sun distance of 92,797,000 mi (149,342,000 km), with a probable error of 59,700 mi (96,100 km). The calculated distance was a significant improvement over several previous estimates.[18]
The telescope used for the discovery of the Moons of Mars was the 26 inch (66 cm) refractor telescope, then located at Foggy Bottom, Washington, DC.[19] In 1893 it was moved to its Northwest DC location.[20]
In 1934, the largest optical telescope installed at USNO saw "first light". This 40 inch aperture instrument[21] was also the second (and final) telescope made by famed optician, George Willis Ritchey. The Ritchey–Chrétien telescope design has since become the de facto optical design for nearly all major telescopes, including the famed Keck telescopes and the space-borne Hubble Space Telescope.
Because of light pollution in the Washington metropolitan area, USNO relocated the 40 inch telescope to Flagstaff, Arizona. A new Navy command, now called the USNO Flagstaff Station (NOFS), was established there. Those operations began in 1955.[22] Within a decade, the Navy's largest telescope, the 61 inch "Kaj Strand Astrometric Reflector" was built; it saw light at Flagstaff in 1964.[23]
USNO continues to maintain its dark-sky observatory, NOFS, near Flagstaff. This facility now oversees the Navy Precision Optical Interferometer.[24]
By the early 1870s the USNO daily noon-time signal was distributed electrically, nationwide, via the Western Union Telegraph Company. Time was also "sold" to the railroads[25] and was used in conjunction with railroad chronometers to schedule American rail transport. Early in the 20th century, the service was broadcast by radio, with Arlington time signal available to those with wireless receivers.
In November 1913 the Paris Observatory, using the Eiffel Tower as an antenna, exchanged sustained wireless (radio) signals with the U.S. Naval Observatory to determine the exact difference of longitude between the two institutions, via an antenna in Arlington, Virginia.[26]
The U.S. Naval Observatory in Washington continues to be a major authority in the areas of Precise Time and Time Interval, Earth orientation, astrometry, and celestial observation. In collaboration with many national and international scientific establishments, it determines the timing and astronomical data required for accurate navigation, astrometry, and fundamental astronomy, and calculation methods — and distributes this information (such as star catalogs)[27] on-line and in the annual publications The Astronomical Almanac and The Nautical Almanac.[28]
Former USNO director Gernot M. R. Winkler initiated the "Master clock" service that the USNO still operates,[29][30] and which provides precise time to the GPS satellite constellation run by the United States Space Force. The alternate Master Clock time service continues to operate at Schriever Space Force Base in Colorado.
In 1990 two departments were established: Orbital Mechanics and Astronomical Applications, with the Nautical Almanac Office a division in Astronomical Applications.[16][31] The Orbital Mechanics Department operated under P. Kenneth Seidelmann until 1994, when the department was abolished and its functions transferred to a group within the Astronomical Applications Department.[16]
In 2010, USNO's astronomical 'department' known as the Naval Observatory Flagstaff Station (NOFS) was officially made autonomous as an Echelon 5 command, separate from, but still reporting to the USNO in Washington. In the alpine woodlands above 7,000 feet altitude outside Flagstaff, Arizona, NOFS performs its national, Celestial Reference Frame (CRF) mission under dark skies in that region.
A house situated on the grounds of the observatory, at Number One Observatory Circle, has been the official residence of the vice president of the United States since 1974. It is protected by tight security control enforced by the Secret Service. The house is separated from the Naval Observatory.
It formerly served as the residence of the observatory's superintendent, and later was the residence of the chief of naval operations, and finally the vice president.[32]
The U.S. Naval Observatory operates two “Master Clock” facilities, one in Washington, DC, and the other at Schriever SFB near Colorado Springs, CO.
The observatory also operates four[34] rubidium atomic fountain clocks, which have a stability reaching 7×10−16.[35] The observatory plans to build several more of this type for use at its two facilities.[33]
The clocks used for the USNO timescale are kept in 19 environmental chambers, whose temperatures are kept constant to within 0.1°C. The relative humidities are kept constant in all maser, and most cesiums enclosures, to within 1%. Time-scale management only uses the clocks in Washington, DC, and of those, preferentially uses the clocks that currently conform reliably to the time reports of the majority. It is the combined ‘vote’ of the ensemble that constitutes the otherwise-fictitious “Master Clock”. The time-scale computations on 7 June 2007 weighted 70 of the clocks into the standard.[33]
The U.S. Naval Observatory provides public time service via 26 NTP[33] servers on the public Internet,[36] and via telephone voice announcements:[37]
The voice of actor Fred Covington (1928–1993)[38] has been announcing the USNO time since 1978.[39]
The voice announcements always begin with the local time (daylight or standard), and include a background of 1 second ticks. Local time announcements are made on the minute, and 15, 30, and 45 seconds after the minute. Coordinated Universal Time (UTC) is announced 5 seconds after the local time.[40] Upon connecting, only the second-marking ticks are heard for the few seconds before the next scheduled local time announcement
The USNO also operates a modem time service,[41] and provides time to the Global Positioning System.
The United States Naval Observatory Instrument shop has been designing and manufacturing precise instrumentation since the early 1900s.[42]
Astronomy and observatories
Technology and technical resources
USNO personnel
These different names for the observatory, and the term 'Hydrographic Office', were used interchangeably until December 1854, when the Secretary of the Navy officially ruled that the proper designation was "The United States Naval Observatory and Hydrographical office".
