The United States Air Force (USAF) conducted a successful launch of the eleventh satellite in the current generation of Global Positioning System (GPS) space assets from Cape Canaveral Air Force Station on October 31. The spacecraft was launched on an Atlas V rocket provided by United Launch Alliance.
GPS IIF satellites are produced by Boeing Network and Space Systems in El Segundo, California. The IIF series provides higher accuracy and better resistance to jamming than the previous generations of GPS satellites. Most of the previous GPS satellites are still operating.
The Air Force confirmed the successful launch approximately 3.5 hours after the liftoff at 12:13 p.m. In a pre-launch conference call, Air Force officials announced the final satellite of the IIF generation is scheduled for launch February 3, 2016.
GPS satellites complete their orbits every 12 hours, and they send a synchronized signal from each individual satellite. The signals are received by a user on the ground at slightly different times because the satellite are at slightly different relative position and have slightly different relative velocity from each other. Originally, GPS signals were degraded for civilian use; President Bill Clinton authorized removal of “selective availability” for civilian users in 2000.
When 4 or more satellites are in contact with a receiver, the receiver can calculate its position to a precision of a few meters.
The last GPS IIF launch will be the final launch of the Boeing manufactured GPS spacecraft. The next generation of GPS spacecraft, termed GPS IIIA, is being manufactured by Lockheed Martin. The first IIIA satellite launch is scheduled for no earlier than calendar year 2017. Lockheed Martin is currently on contract for 4 IIIA satellites.
The GPS III spacecraft contain a new civilian-use signal, a safety of life signal, and a new military use signal. The GPS III spacecraft signal power at the Earth’s surface will be greater than previous GPS generations.