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|Country of origin||United States|
|Satellites in orbit||31|
|First launch||February 1978|
|Regime(s)||6x MEO planes|
|Orbital height||20,180 km (12,540 mi)|
The Global Positioning System (GPS) is a space-based radionavigation system owned by the United States Government (USG) and operated by the United States Air Force (USAF)." It is a global navigation satellite system (GNSS) that provides geolocation and time information to a GPS receiver in all weather conditions, anywhere on or near the Earth where there is an unobstructed line of sight to four or more GPS satellites. The GPS system operates independently of any telephonic or internet reception, though these technologies can enhance the usefulness of the GPS positioning information. The GPS system provides critical positioning capabilities to military, civil, and commercial users around the world. The United States government created the system, maintains it, and makes it freely accessible to anyone with a GPS receiver. However, the US government can selectively deny access to the system, as happened to the Indian military in 1999 during the Kargil War.
The GPS project was launched in the United States in 1973 to overcome the limitations of previous navigation systems, integrating ideas from several predecessors, including a number of classified engineering design studies from the 1960s. The U.S. Department of Defense (DoD) developed the system, which originally used 24 satellites. It became fully operational in 1995. Roger L. Easton of the Naval Research Laboratory, Ivan A. Getting of The Aerospace Corporation, and Bradford Parkinson of the Applied Physics Laboratory are credited with inventing it.
Advances in technology and new demands on the existing system have now led to efforts to modernize the GPS and implement the next generation of GPS Block IIIA satellites and Next Generation Operational Control System (OCX). Announcements from Vice President Al Gore and the White House in 1998 initiated these changes. In 2000, the U.S. Congress authorized the modernization effort, GPS III.
|Satellite launches||Currently in orbit
|(Last update: March 9, 2016)
GPS time relationship
(precise satellite orbit)
(satellite network synopsis,
|L1||1575.42 MHz||Coarse-acquisition (C/A) and encrypted precision (P(Y)) codes, plus the L1 civilian (L1C) and military (M) codes on future Block III satellites.|
|L2||1227.60 MHz||P(Y) code, plus the L2C and military codes on the Block IIR-M and newer satellites.|
|L3||1381.05 MHz||Used for nuclear detonation (NUDET) detection.|
|L4||1379.913 MHz||Being studied for additional ionospheric correction.|
|L5||1176.45 MHz||Proposed for use as a civilian safety-of-life (SoL) signal.|
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