WASHINGTON — The U.S. Air Force is proposing to scale back its planned procurement of rockets and GPS navigation satellites in 2015 while beginning long-deferred work on a new weather satellite system, the service said in budget request documents for the upcoming fiscal year.

At this time last year, the Air Force was planning on buying two additional next-generation GPS 3 navigation satellites next year from prime contractor Lockheed Martin Space Systems of Denver. Now the service plans on buying just one, according to the budget documents, which were released March 4.

Currently Lockheed Martin is under contract to build eight GPS 3 satellites, which are designed to be more accurate and less vulnerable to enemy jamming than previous generations of GPS craft. With most of its investment in development of the new craft behind it, the Air Force expected to pay about $223 million apiece for two additional satellites in 2015, according to documents that accompanied the 2014 request.

The Air Force currently has 31 earlier-generation GPS satellites active on orbit and has launched five of the 12 satellites in the current series of satellites, called GPS 2F. The first GPS 3 satellite is scheduled to launch in late 2015. 

The Air Force’s 2015 budget request also includes money to begin development of a new generation of polar-orbiting weather satellites. Known as the Weather System Follow-On (WSF), the program would replace the long-running Defense Meteorological Satellite Program. 

Gen. William Shelton, commander of Air Force Space Command, said in January the new military weather satellites could be a showcase for disaggregation, an emerging vision for space that favors smaller, less complex satellites, hosted payloads and other deployment schemes versus the large, complex systems that have been the standard for decades.

“WSF will take a disaggregated system-of-systems approach to meet specific Department of Defense needs while leveraging near-term civilian and international partnerships,” the Air Force’s 2015 budget documents said. “WSF will be comprised of a group of systems to provide timely, reliable, and high quality space-based remote sensing capabilities that meet global environmental observations of atmospheric, terrestrial, oceanographic, solar-geophysical and other validated requirements.”

The Air Force’s second-to-last Defense Meteorological Satellite Program satellite, Flight 19, is scheduled to launch aboard a United Launch Alliance Atlas 5 rocket in April. The Air Force has been studying options for a follow-on system ever since the cancellation in 2010 of an overbudget civil-military system.

Shelton had said the first of the new-generation weather satellite platforms could launch around 2020.

Meanwhile, the Air Force plans to purchase two fewer launches than expected in 2015 under  its Evolved Expendable Launch Vehicle (EELV) program. The service’s 2014 budget request outlined plans to buy five rockets at a cost of approximately $883 million in 2015. The documents accompanying the 2015 request indicate that the Air Force now plans to buy three launches during the year. 

“The EELV program has been aligned with satellite launch schedules in FY 2015,” the documents said.

The difference reflects “newly negotiated contract savings,” budget documents said. In December, United Launch Alliance and the Air Force announced they had reached terms for the first batch of rockets in a long-awaited block buy of EELV rockets and claimed they saved as much as $4.4 billion.

Further details of U.S. President Barack Obama’s 2015 Pentagon budget request, including military space programs, are expected to be released the week of March 10.

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Mike Gruss is a senior staff writer for SpaceNews. He joined the publication in January 2013 to cover military space. Previously, he worked as a reporter and columnist for The Virginian-Pilot in Norfolk, Va. and The Journal Gazette in Fort Wayne, Ind. He...