The U.S. Air Force's upcoming fifth and sixth satellites in its missile warning constellation will have a new satellite bus. CREDIT: Lockheed Martin.

Updated June 12 at 1:25 p.m.

WASHINGTON – The U.S. Air Force will use Lockheed Martin’s standard satellite bus on the forthcoming fifth and sixth satellites of its Space Based Infrared System missile warning constellation as part of a much discussed “refresh” of the program’s technology, the service announced June 9.

The move, Air Force officials said, will open more options as the service considers its next-generation missile-warning architecture by allowing it to treat the bus separately from the payload. The current SBIRS bus, or satellite platform, is tailored specifically to the mission.

Last December, SBIRS prime contractor Lockheed Martin proposed using the latest variant of its A2100 satellite bus for the fifth and sixth satellites. Air Force officials had been studying the idea since then.

Sunnyvale, California-based Lockheed Martin Space Systems revamped the bus, which is used for both government and commercial programs, to make it simpler and less expensive using internal research and development dollars. As a result, Air Force officials said the change on SBIRS comes at no cost to the government.

“The modernized satellite provides a pathway for implementing the next-generation of capabilities being pursued under the Air Force’s Space Modernization Initiative,” Col. Mike Guetlein, commander of the Air Force’s remote sensing division, said in a June 9 press release. “In the end, the next generation capabilities will enable warfighters to see dimmer targets faster which will allow commanders to keep our troops on the battlefield as well as our nation and our allies, safe.”

In a June 10 press briefing, Guetlein said the change is one of the most significant upgrades in the program’s history.

SBIRS satellites are equipped with infrared sensors that detect and to some extent track missile launches around the world. The constellation consists of dedicated satellites in geosynchronous orbit and missile warning payloads hosted aboard classified satellites operating in highly elliptical orbit.

The Air Force in June 2014 awarded Lockheed Martin a $1.86 billion production contract for the fifth and sixth SBIRS satellites, which according to the U.S. Government Accountability Office are expected to be available for launch in 2020 and 2021, respectively. Two dedicated SBIRS satellites have launched to date.

In the press release, the Air Force said the new bus would increase resiliency, reduce obsolescence, and provide savings on future SBIRS satellites. It also improves the vehicle’s power and propulsion, according to a Lockheed Martin press release.

The improved power system will allow the Air Force to place additional payloads on the SBIRS satellites, an option not available with the current bus, Guetlein said in the briefing.

The Air Force is still working on an analysis of future missile warning alternatives that according to the GAO is expected to wrap up this fall.

In recent years, U.S. lawmakers have asked the Air Force for greater detail on how the service planned to use the $1 billion it claimed to have saved by buying the fifth and sixth SBIRS satellites together rather than serially. Given that the SBIRS program dates back to the 1990s, some in Congress are wary of launching satellites featuring decades old technology.

In response, the service said much of that money was funneled through the its multi-program Space Modernization Initiative account, including what it calls Evolved SBIRS, the next iteration of the program.

In September, the Air Force sent a report to congressional defense committees outlining a series of cost-cutting options and ways to address obsolescence issues, including using the A2100 platform.

The GAO’s total estimated cost of the SBIRS program is nearly $19 billion.

Mike Gruss covers military space issues, including the U.S. Air Force and Missile Defense Agency, for SpaceNews. He is a graduate of Miami University in Oxford, Ohio.