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Timation
The Timation satellites were conceived, developed, and launched by the Naval Research Laboratory in Washington, D.C. beginning in 1964. The concept of Timation was to broadcast an accurate time reference for use as a ranging signal to receivers on the ground. On 31 May 1967 the Timation-1 satellite was launched. This was followed by the Timation-2 satellite launch in 1969. The results of this program and Air Force Project 621B formed the basis for the Global Positioning System (GPS). The Navy's contribution to the GPS program continued to be focused on ever more accurate clocks.
There is a historical connection between accurate time keeping, navigation, and the Navy. In 1714 the British government passed the ''Longitude Act'' (see longitude prize) to create an incentive to solve the problem of navigation at sea. The solution, developed by John Harrison, was an accurate clock which could compare local time to Greenwich, England time. To this day Greenwich Mean Time is the reference time for the planet, and in the United States, the official time for the Department of Defense is kept by the United States Navy at the U.S. Naval Observatory in Washington, D.C.. This is kept in sync with the official civilian time reference maintained by NIST and contributes to the International Atomic Time.〔(【引用サイトリンク】url=http://www.nist.gov/pml/div688/utcnist.cfm#usno )〕
== See also ==
* Time signal
* Global Positioning System (GPS)
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