thumb|right|250px|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
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, which with the "
Master Clock" , 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.
History
Aerial view of the U.S. Naval Observatory.
Established by order of 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 the project, which was completed in 1844.
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. Initially located downtown in
Foggy Bottom (near the
Lincoln Memorial), the observatory was moved to its present location in 1893, atop Observatory Hill overlooking
Massachusetts Avenue, amidst perfectly
circular grounds.
The first superintendent was Navy Commander
Matthew Fontaine Maury. Maury had the world's first
vulcanized time ball, created to his specifications by
Charles Goodyear for the U.S. Observatory. It was the first time ball in the United States, being placed into service in 1845, 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, enabling all ships and civilians 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, and by the early 1870's the Observatory's daily noon time signal was being distributed nationwide via the
Western Union Telegraph Company. Time was also "sold" to the railroads and was used in conjunction with
railroad chronometers to schedule American rail transport. Early in the 20th century, the Arlington Time Signal broadcast this service to
wireless receivers.
The names "National Observatory" and "Naval Observatory" were both used for 10 years, until a ruling was passed to use only the term "Naval Observatory".
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. He spent many nights at the observatory with Maury, watching and charting the stars, which had always been one of Adams' avocations.
In November 1913, the
Paris Observatory, using the
Eiffel Tower as an
antenna, exchanged sustained wireless (radio) signals with the United States Naval Observatory, using an antenna in
Arlington, Virginia to determine the exact difference of longitude between the two institutions.
Naval Observatory Flagstaff Station in Operation.
In 1934, the last large telescope to be installed at USNO saw "first light". This 40-inch aperture instrument was also the second (and final) telescope made by famed optician,
George Ritchey. The
Ritchey-Chrétien telescope design has since become the defacto optical design for nearly all major telescopes, including the famed
Keck telescopes and the spaceborne
Hubble Telescope. Unfortunately, light pollution forced USNO to think of other more viable locations to continue work, and so began a search. The final dark sky site chosen was
Flagstaff, Arizona, and so the 40-inch telescope was moved to that location, beginning operations at the new
Naval Observatory Flagstaff Station (NOFS) in 1955. . Within a decade, the Navy's largest telescope, the 61-inch "
Kaj Strand Astrometric Reflector" was built, seeing light at NOFS in 1964.
The modern United States Naval Observatory continues to be a major authority in the areas of time-keeping 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
astronomical catalogs ) in the
Astronomical Almanac, the
Nautical Almanac, and online .
Perhaps it is best known to the general public for its highly accurate ensemble of
atomic clocks and its year 2000 Timeball replacement. The site also houses the largest astronomy library in the United States (and the largest astrophysical periodicals collection in the world). The library includes a large collection of rare, often famous, physics and astronomy books from across the past millenium.
USNO continues to maintain its
dark-sky observatory,
NOFS, near
Flagstaff,
Arizona, which also now oversees the
Navy Prototype Optical Interferometer . NOFS opens to the public annually in the autumn one weekend . The Alternate Master Clock, mentioned above, also continues to operate at
Schriever AFB in
Colorado.
Official Residence of the Vice President of the United States
Since 1974, and separated from auspices of the Naval Observatory,
Number One Observatory Circle, a house situated in the grounds of the observatory (formerly the residence of its superintendent, and later the home of the
Chief of Naval Operations), has been the official residence of the
Vice President of the United States.
According to a May 15, 2009 blog posting by
Newsweek's Eleanor Clift, Vice President
Joe Biden recently revealed the existence of what Clift described as a bunker-like room in the residence. The bunker is believed to be the secure, undisclosed location former Vice President
Dick Cheney remained under protection in secret after the
9/11 attacks. According to Clift's report:
"Biden said a young naval officer giving him a tour of the residence showed him the hideaway, which is behind a massive steel door secured by an elaborate lock with a narrow connecting hallway lined with shelves filled with communications equipment."
Biden's press office subsequently issued a statement denying the bunker report, suggesting that Biden had instead been describing "an upstairs workspace".
Time service
Atomic clock ensemble at the U.S. Naval Observatory
The U.S. Naval Observatory's time service can be accessed by telephone or via the Internet:
- *719-567-6742 (Colorado Springs)
- *202-762-1401 (Washington, D.C.)
- *USNO operates several NTP servers for time synchronization over the Internet
The voice of
Fred Covington (1928–1993) has been announcing the USNO time since 1978.
See also
