WASHINGTON — The U.S. Senate’s newly drafted defense spending bill for 2015 directs the Air Force to allocate at least $20 million for work on a space-based digital navigation instrument as a possible alternative to the payload developed for the service’s new-generation GPS 3 satellites.

Those satellites are two years behind schedule due primarily to delays with the payload being developed by Exelis Geospatial Systems of Rochester, New York. Those delays have frustrated the Air Force, prompting the service and GPS 3 prime contractor Lockheed Martin Space Systems of Denver to explore possible alternatives.

At least five unidentified companies responded to a Lockheed Martin request for information on potential providers, and officials with Boeing Space and Intelligence Systems of El Segundo, California, say they have been working on digital GPS technologies. Boeing is prime contractor on the GPS 2F satellites currently being launched but lost to Lockeed Martin in the competition for GPS 3 system, now slated to begin launching in 2016.

The Senate Appropriations defense subcommittee, which drafted the bill, “believes that early Air Force investment, when combined with industry investment, into the development of a digital navigation payload will significantly reduce cost and schedule risk for the future GPS constellation,” a report accompanying the legislation said.

The $20 million is part of an additional $32.9 million recommended by the subcommittee for the GPS 3 space modernization initiative account.

In a July 17 email, Chip Eschenfelder, a Lockheed Martin spokesman, said the company believes the technical challenges with the Exelis-built payload have been resolved and that the first unit is expected to be delivered this fall. “Once the first navigation payload is delivered, we are into the production phase,” he said.

Exelis has built or had a role in every GPS payload since the program’s inception nearly three decades ago and is expected to be the supplier for at least the first eight GPS 3 craft, all of which are under contract. How the Air Force will continue buying GPS 3 satellites after the first eight remains to be seen.

Senate Appropriators Weigh In

Like many of the Air Force’s satellite constellations, GPS has been mentioned as a candidate for disaggregation, a concept that entails dispersing capabilities currently concentrated on large platforms among smaller ones. Skeptics within the Defense Department have questioned whether disaggregation will save money and whether the Air Force can muster the investment resources necessary to develop a new constellation architecture.

The Senate bill nonetheless appears to endorse the idea. “The Committee firmly believes that movement away from large satellites, where possible, will result in significant cost savings and reduce the schedule to deliver payloads into orbit.”

The Air Force has effectively adopted the disaggregated approach on its new Defense Weather Follow-on satellite program, which is fully funded in the Senate spending bill.

The draft bill also includes $20 million next year for the Air Force-led Operationally Responsive Space (ORS) Office, which was established at Kirtland Air Force Base, New Mexico, in 2007 and is tasked with quickly developing low-cost space capabilities in response to emerging military needs. The Air Force has been seeking to close the office — the service requested no money for the office in 2015 — but has been stymied to date by Congress.

The ORS office is expected to begin work this year on at least one of two proposed satellites. One of those, ORS-2, would carry a radar sensor for ground reconnaissance; the other, ORS-5, would be used for space surveillance.

The bill also includes language directing the Air Force to reconsider plans to launch the second of two refurbished military weather satellites that were built in the 1990s. The Air Force spent hundreds of millions of dollars refurbishing and storing the last two satellites in the Defense Meteorological Satellite Program, which for decades has provided global weather data to support military and intelligence-gathering operations. The first of those satellites, DMSP Flight 19, was launched in early April, but the Air Force has been noncommital about launching the second.

Notionally, DMSP Flight 20 is expected to launch in 2020, but the Senate appropriations report said storing the satellite until then would cost $425 million.

“The Committee questions the Air Force’s current plan to launch this satellite in 2020 at a significant cost to the Government for a capability that may be met through other space-based assets,” the report said.

The Senate panel also suggested partnering with Canada on its planned satellite system for providing communications and weather monitoring in the Arctic and asked the Air Force for a plan on arctic coverage for the future.

The committee also took note of the long delay in awarding a $914 million contract to Lockheed Martin Mission Systems and Training of Moorestown, New Jersey, to build the Air Force’s next-generation Space Fence space surveillance system and trimmed $60 million from the service’s $214 million request for the program.

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...