GPS Block IIF
Artist's impression of a Block IIF GPS satellite in orbit
|Country of origin||United States|
|Orbit regimes||Semi-synchronous MEO|
|Operator||US Air Force|
|First launch||GPS IIF SV-1
28 May 2010, 03:00 UTC
|Average mass||1,630 kg (3,590 lb)|
GPS Block IIF, or GPS IIF is an interim class of GPS satellite, which will be used to keep the Navstar Global Positioning System operational until the GPS Block IIIA satellites become operational. They are being built by Boeing, and will be operated by the United States Air Force following their launch by United Launch Alliance, using Evolved Expendable Launch Vehicles. They will be the final component of the Block II GPS constellation to be launched. The spacecraft have a mass of 1,630 kilograms (3,590 lb) and a design life of 12 years. Like earlier GPS satellites, Block IIF spacecraft operate in semi-synchronous medium Earth orbits, with an altitude of approximately 20,460 kilometres (12,710 mi), and an orbital period of twelve hours.
The satellites will replace the GPS Block IIA satellites which were launched between 1990 and 1997 and were designed to last 7.5 years. Eleven of those satellites are still in use, including four that were launched in 1992.
Because the Evolved Expendable Launch Vehicles are more powerful than the Delta II, which was used to orbit earlier Block II GPS satellites, they can place the satellites directly into their operational orbits. As a result, Block IIF satellites do not carry apogee motors. The original contract for Block IIF, signed in 1996, called for 33 spacecraft. This was later reduced to 12, and programme delays and technical problems pushed the first launch from 2006 to 2010.
- Broadcasting L5 "safety of life" navigation signal demonstrated on USA-203
- Broadcasting a new M-code signal
- Doubling in the predicted accuracy
- Better resistance to jamming
- Reprogrammable processors that can receive software uploads
- The first GPS satellites not to have Selective Availability hardware installed which degraded civilian accuracy when turned on in the original satellite fleet
The first GPS IIF satellite, Space Vehicle 1, was launched by a Delta IV-M+(4,2) rocket at 03:00 UTC on 28 May 2010. The launch took place from Space Launch Complex 37B at the Cape Canaveral Air Force Station. It was the 61st GPS satellite to launch and the 50th GPS launched on a Delta.
A third GPS IIF satellite, GPS IIF SV-4, was launched on a Delta IV-M+(4,2) rocket at 12:10 UTC on 4 October 2012. This launch came shortly before the 10th anniversary of the inaugural Delta IV launch. This satellite went operational on November 13, 2012.
- Beidou navigation system
- Compass navigation system
- Galileo (satellite navigation)
- Quasi-Zenith Satellite System
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- Tariq Malik (28 May 2010). "Air Force Launches Advanced New GPS Satellite". SPACE.com.
- "Delta IV Set to Launch GPS IIF SV-1". United Launch Alliance. Retrieved 27 May 2010.
- "United Launch Alliance GPS IIF-2". United Launch Alliance. Retrieved 16 July 2011.
- "United Launch Alliance GPS IIF-3". United Launch Alliance. Retrieved 8 October 2012.
- "ULA Atlas V sets sail with new GPS satellite". NASA Space Flight. 15 May 2013. Retrieved 15 May 2013.
- "Orbit Data and Resources on Active GNSS Satellites". GPS World. Retrieved 6 March 2014.
- "United Launch Alliance Successfully Launches 25th Delta IV Mission Carrying Global Positioning System Satellite for the U.S. Air Force". United Launch Alliance. Retrieved 6 March 2014.