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Samples of three GPS satellites' orbits over a five-year period (2013 to 2018) USA-242 · USA-239 · USA-151 · Earth As of 22 January 2025, 83 Global Positioning System navigation satellites have been built: 31 are launched and operational, 3 are in reserve or testing, 43 are retired, 2 were lost during launch, and 1 prototype was never launched. 3 Block III satellites have completed ...
The GPS date and time, and the satellite's status. The ephemeris: precise orbital information for the transmitting satellite. The almanac: status and low-resolution orbital information for every satellite. An ephemeris is valid for only four hours, while an almanac is valid–with little dilution of precision–for up to two weeks. [7]
GPS Block III is the first series of third-generation GPS satellites, incorporating new signals and broadcasting at higher power levels. In September 2016, the United States Air Force awarded Lockheed Martin a contract option for two more Block III satellites, setting the total number of GPS III satellites to ten. [ 22 ]
The longitude of the ascending node, also known as the right ascension of the ascending node, is one of the orbital elements used to specify the orbit of an object in space. Denoted with the symbol Ω , it is the angle from a specified reference direction, called the origin of longitude , to the direction of the ascending node (☊), as ...
These are used for Global Navigation Satellite System spacecraft, such as GPS, GLONASS, Galileo, BeiDou. GPS satellites orbit at an altitude of 20,200 kilometers (12,600 mi) with an orbital period of almost 12 hours. [8] Geosynchronous orbit (GSO) and geostationary orbit (GEO) are orbits around Earth matching Earth's sidereal rotation period.
Orbital elements are the parameters required to uniquely identify a specific orbit. In celestial mechanics these elements are considered in two-body systems using a Kepler orbit . There are many different ways to mathematically describe the same orbit, but certain schemes, each consisting of a set of six parameters, are commonly used in ...
The United States' Global Positioning System (GPS) reached Full Operational Capability on 17 July 1995, [9] completing its original design goals. Advances in technology and new demands on the existing system led to the effort to modernize the GPS system. In 2000, the U.S. Congress authorized the effort, referred to as GPS III.
GC number (Ground Control number, Russian: системный номер, номер по наземному комплексу управления) is the spacecraft number in almanac. [1] It only has to be unique during life time of each satellite. Numbers are subject to reuse. Some catalogs mistakenly used GC numbers for historical ...