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.

WASHINGTON — Lockheed Martin Space Systems of Sunnyvale, California, has delivered the payload for the fourth dedicated satellite in the U.S. Air Force’s primary missile warning satellite constellation.

The infrared payload, built by Northrop Grumman Electronic Systems of Linthicum, Maryland, still needs to be integrated and tested on the Space Based Infrared System satellite, which is expected to launch in summer 2016, Air Force officials said in an Oct. 6 press release. Lockheed Martin is prime contractor on the program.

“The completion of this payload is a critical milestone keeping us on schedule for delivering the SBIRS GEO-4 satellite to the Air Force in 2016,” Louie Lombardo, director of Lockheed Martin’s SBIRS Follow-on Production program, said in an Oct. 8 press release.

The SBIRS GEO-4 payload includes highly sophisticated scanning and staring sensors, providing improved infrared sensitivity and more-timely coverage than the legacy Defense Support Program satellites, some of which are still in operation.

SBIRS scanning sensors provide wide-area surveillance of missile launches and natural phenomena, while the staring sensors are used to observe smaller areas of interest with superior sensitivity.

“It takes a tremendous amount of work and dedication to bring these systems together, but it pays off when we deliver new capabilities to the warfighter,” Air Force Maj. Jon Seal, the vehicle manager for GEO-4, said in a press release.

The fourth GEO satellite will fill out the geosynchronous component of the initial SBIRS constellation. The system also includes infrared payloads hosted aboard classified satellites in highly elliptical orbits.

“The performance of payloads on-orbit has been excellent and demonstrates unique capabilities that are needed to address current and evolving threats,” Anne Ostroff, vice president of Northrop Grumman’s military/civil space and ground business area, said in the Lockheed Martin press release.

Lockheed Martin is under contract for full production of the fifth and sixth geosynchronous SBIRS satellites.

The first two dedicated SBIRS satellites are on orbit. The third, known as GEO-3, is currently undergoing vacuum testing and is expected to be delivered in 2015.

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...