The U.S. Air Force is extending by nine months the four ground-segment study contracts for its next-generation GPS satellite navigation system to reduce risk and preserve the flexibility to accelerate the space segment, the service announced June 23.

Four companies are studying the GPS 3 Operational Control Segment under contracts awarded in the summer of 2005: Northrop Grumman Corp. of Los Angeles; General Dynamics C4 Systems of Scottsdale Ariz.; Raytheon Co. of Waltham, Mass.; and Integral Systems of Lanham, Md. Those contracts, originally valued at between $1.1 and $1.4 million apiece, were supposed to run for six months.

In a written response to questions, Tonya Racasner, a spokeswoman for the Air Force, said the value of the contract extensions have not yet been determined. She said the extensions would help reduce technical and programmatic risks associated with developing the GPS 3 space and ground segments separately.

The award of the Operational Control Segment prime contract is now slated for the second quarter of 2007, the Air Force said.

Lockheed Martin Corp. of Bethesda, Md., and Boeing Co. of Chicago are competing to build the GPS 3 satellites, which are expected to offer more accurate and robust navigation signals than prior systems. The satellites originally were supposed to start launching in 2009, but that schedule has shifted back and forth several times, with initial deployment now scheduled for 2013.

The GPS 2R-series navigation satellites currently being launched are built by Lockheed Martin. Boeing is building a follow on series dubbed GPS 2F that will serve as a bridge to the GPS 3 constellation.

Air Force officials have acknowledged that the GPS 2F program has run into developmental snags. Boeing is under contract to build 12 GPS 2F satellites, which are slated to begin launching in 2008 .

In a notice announcing the ground segment contract modifications, the Air Force said that among the areas to be studied under the extensions are “approaches to support an accelerated GPS 3A space vehicle launch” as well as ground segment and space vehicle “synchronization.”