Infrastructure
Positioning, Navigation, and Timing (PNT) Satellites
2007 – GPS
The U.S. Navigation Signal Timing and Ranging Global Positioning System (NAVSTAR GPS or GPS) continues to be the only fully operational navigation constellation and therefore the most popular. GPS consists of ## active satellites in ## medium Earth orbit planes. According to the Department of Defense (DoD), “the fundamental concept of GPS is to use simultaneous distance measurements from ## satellites to compute the position and time of any receiver.” The GPS signal is available at no cost to users around the world and has spawned many commercial applications.
2005 – QZSS
Japan is developing the Quasi-Zenith system, a regional augmentation of the GPS signal, with a 2008 planned launch.
2005 – Galileo
Europe launched the first test satellite in the Galileo system in December 2005.
2005 – GPS
The U.S. NAVSTAR (Navigation Signal Timing and Ranging) GPS constellation consists of ## active and ## spare satellites in MEO. According to the DoD, the fundamental concept of GPS is to use simultaneous distance measurements from ## satellites to compute the position and time of any receiver. The GPS signal is available without cost to users around the world and has spawned many commercial applications.
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