GPS Source GPS Fact Sheet 2007

Constellation/System: The NAVSTAR GPS (Navigation Satellite Timing and Ranging Global Positioning System) is all weather, continuously available, satellite-based RF positioning system providing highly accurate 3D PVT (Position Velocity & Time)

• The baseline system is specified for 24 satellites; however the system currently employs more than 24 satellites.
• The constellation contains 6 orbital planes inclined 55 degrees to the equator. Each plane contains 4-5 active satellites.
• Satellite altitude is 10,898 nmi. or 20,183 Km or 12,500 statute miles from mean surface of the Earth.
• Satellites are in an 11 hour 58 minute orbital periods.
• The system is implemented and operated by the U.S. DoD. FOC (Full Operation Constellation) was declared on 27 April 95.
• Navigation parameters are based in the NIMA (National Imaging and Mapping Agency) (formerly DMA) ECEF (Earth Centered Earth Fixed)
• WGS (World Geodetic System) 84 datum; A world wide common grid reference system.
• Transmissions are a CDMA spread spectrum signals.
• Time base for system is UTC (USNO United States Naval Observatory).
• The current system consists mainly of Boeing (formerly Rockwell Collins) Block II/IIA satellites.
• Lockheed Martin Block IIR satellites are currently being launched into the configuration.

• Runs from 700W EOL (End of Life) power source of solar panels and batteries.
• 12 L-band right hand circularly polarized helical elements form the phased array antenna.
• 2 Rubidium and 2 Cesium atomic clocks onboard II/IIA S/C. 3 Rubidium on IIR’s. UTC time to better than 30ns.
• Two Navigation carrier signals for transmission: L1 at 1575.42MHz and L2 at 1227.6MHz.
• 36 available unique PRN (Pseudo Random Noise) codes, 4 of these are reserved.
• 7.5 year design lifetime

Signal characteristics Message: Navigation message is at 50bps. Message structure format, 1500-bit frame made up of 5 sub-frames (30 seconds). Each sub-frame is 300 bits long. Superframe consists of 25 subframes.

Carriers: