BY JUSTIN RAY
Posted: June 27, 2011
A Global Positioning System satellite has been loaded aboard its ride to space, arriving Monday at Cape Canaveral’s Complex 37 for mounting atop the United Launch Alliance Delta 4 rocket.
Liftoff of the GPS 2F-2 spacecraft is scheduled for July 14 during a 19-minute window extending from 2:49 to 3:08 a.m. EDT (0649-0708 GMT).
The launch is timed to deliver the satellite into the GPS constellation to replace a 20-year craft that has long exceeded its expected lifespan.
GPS satellites fly about 11,000 miles above the planet and emit continuous navigation signals that allow users to find their precise position in latitude, longitude and altitude and determine time. Originally built for the U.S. military, the GPS service has spread across the world as an indispensable commercial utility.
The Air Force is in the midst of further upgrading the GPS network by deploying a new breed of satellite that features improved accuracy, enhanced internal atomic clocks, better anti-jam resistance, a civil signal for commercial aviation, a longer design life and reprogrammable onboard processors to evolve with future needs.
A dozen of these new satellites in the Block 2F series are being built by The Boeing Company. The first was successfully launched from the Cape on May 27, 2010.
GPS 2F-2 was shipped April 19 from Boeing’s manufacturing facility in El Segundo, Calif., to the Florida spaceport in a C-17 Globemaster III airlifter. After arriving at the Skid Strip, it was taken to Area 59 were GPS spacecraft undergo their pre-flight preps.
Launch base testing, the filling of maneuvering propellants and encapsulation within the two-piece rocket nose cone were among the activities accomplished at the satellite’s cleanroom hangar.
A motorized trailer then carried the 3,400-pound satellite up the road to Complex 37 early Monday. It was positioned on the oceanside of the mobile service gantry and hoisted into the pad tower for bolting to the rocket’s second stage.
Today’s GPS constellation is comprised of 31 operational satellites, including 11 Block 2A’s made by Boeing, 12 Block 2R’s and seven 2R-Modernized spacecraft built by Lockheed Martin, and Boeing’s first Block 2F.
Ground controllers expect to have the GPS 2F-2 satellite checked out and ready for use about 30 days after launch, the Air Force says.
The new spacecraft will occupy the Plane D, Slot 2A location of the navigation network, which is divided into six orbital groupings with multiple satellites flying in each.
The craft takes over the position held by the GPS 2A-11 satellite, which was launched by a Delta 2 rocket from Cape Canaveral on July 3, 1991.
Remarkably, that aging bird continues to function despite the loss of some redundant systems and far outlasting its design life. It will be relocated within the same orbital plane as a reinforcement while living out its remaining usefulness.
The Air Force recently completed an 18-month shuffling of six GPS satellites in the constellation to achieve “the most optimal geometry in its 42-year history,” according to the service. The effort will boost signal reception to users in difficult terrains and the system’s overall accuracy worldwide.