lørdag 16. juli 2011

GPS IIF nr. 2 er i bane og sender "her er jeg" signal

"Alle" er avhengig av GPS, ser det ut til. Da er du sikkert interessert i "etterfylling" av nye satellitter. Den første GPS Block IIF er allerede operativ, og den andre ble skutt opp i dag. Den forteller at alt er i orden og at den er klar for utsjekk av systemer. Her noen harde data:
Manufacturer Boeing
Country of Origin United States
Applications Navigation satellite
Orbit regimes Semi-synchronous MEO
Operator US Air Force
Lifetime 12 years
Status In Production:
Built 2
On order 10
First launch GPS IIF SV-1 28 May 2010, 03:00 UTC
Typical spacecraft:
Average mass 1,630 kg (3,600 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 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 (3,600 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.
New characteristics
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 hardware Selective Availability installed which could degrade civilian accuracy. Ill.: Boeing

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