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With days numbered, Delta 4 rocket poised to launch GPS satellite

Irene Klotz, Spaceflight Correspondent
Mar 25, 2015, 12:07 UTC

Sen—A United Launch Alliance Delta 4 rocket is poised for liftoff Wednesday to deliver the ninth in a series of upgraded Global Positioning System satellites into orbit for the U.S. military, civilian agencies and commercial users.

Launch from Cape Canaveral Air Force Station is Florida is scheduled for 2:36 p.m. EDT. Meteorologists are predicting an 80 percent chance the weather will be suitable for launch.

Two more Block 2F GPS satellites are expected to be launched this year, with the 12th and final member of the Boeing-built constellation slated to fly in January. 

To deliver the spacecraft into its operational orbit some 12,700 miles above Earth and inclined 55 degrees relative to the equator, the Delta 4 will fly with a pair of strap-on solid rocket motors, one of several medium-lift configurations.

In an effort to better compete with Space Exploration Technologies, or SpaceX, ULA is proposing to phase out all but the heaviest-lift version of the Delta 4 and rely on the less expensive Atlas 5 for GPS and similar class missions.

The proposal is controversial since the Atlas 5 uses Russian-made engines, future imports of which have been banned by Congress. The trade sanctions are in response to Russia’s invasion of Ukraine.

The Air Force is expected to clear SpaceX to compete for its launch business as early as June, a move that likely will end ULA’s monopoly.

ULA plans to switch to a U.S.-made engine under development by startup Blue Origin around 2019. The company’s next-generation rocket design will be unveiled at the U.S. Space Symposium in Colorado Springs, Colorado, next month.

The GPS 2F-9 will replace an older-generation spacecraft that has been in orbit since 1993, said Bill Cooley, a brigadier general who oversees the Air Force Space and Missile Systems Center's Global Positioning System Directorate.

The new satellite will join a network of of 31 operational and seven spare spacecraft.