BOSTON — The U.S. Air Force’s Space and Missile Systems Center (SMC) awarded contracts to two companies for designs on a new missile warning satellite system, the service announced Dec. 4.

The center awarded contracts to General Dynamics Advanced Information Systems of Gilbert, Ariz., and Northrop Grumman Space Technology of Redondo Beach, Calif., to evaluate space and ground system approaches for the proposed Alternative Infrared Satellite System (AIRSS), according to a Dec. 4 news release. The awards are worth $23.3 million and $24.8 million, respectively.

The Air Force said in its release that the work is intended to provide the service with cost, schedule and technical insights that will help it decide whether to pursue the AIRSS effort as a formal program, a milestone the Air Force calls Key Decision Point B. A positive decision at that would lead to a formal request for proposals, the service said in its press release.

The Air Force is considering AIRSS as a possible replacement for the Space Based Infrared System (SBIRS) missile warning satellites. The Pentagon restructured the SBIRS program in late 2005 due to excessive cost growth, reducing the number of satellites it would acquire from five to no more than three. A decision on whether to buy a third SBIRS satellite — Lockheed Martin Space Systems of Sunnyvale, Calif., is prime contractor — is expected next year.

In the meantime, the Air Force is studying the alternative system. In September, the service awarded separate contracts to Raytheon Co., of Waltham, Mass., and SAIC, of San Diego, to design and develop prototype AIRSS sensors for testing. The 18-month contracts are worth $24 million and $54 million, respectively.

Northrop Grumman and General Dynamics will be working on designs to integrate the AIRSS satellites, according to a written response to questions from 2nd Lt. Shirali Patel, a spokeswoman for the AIRSS program. The companies will be translating the military’s requirements for the missile warning sensors into systems engineering designs that ultimately will help the Air Force develop a formal request for proposals for the AIRSS program, she said.

“Their analysis is intended to provide the Air Force with insight into the cost of satisfying the technical requirements in order to avoid potential cost growth from a poorly understood requirement,” Patel said.

The companies may develop some hardware models in the later stages of their work if the Air Force believes there is sufficient engineering uncertainty to merit a prototype component or subsystem, Patel said.

Some of the challenges that Northrop Grumman and General Dynamics will have to confront include designing the AIRSS system so that it can work in concert with the SBIRS satellites, Patel said.

Tim Frei, vice president for intelligence, surveillance and reconnaissance programs at Northrop Grumman Space Technology, said that the company is looking forward to applying approximately 40 years of experience with missile warning programs as it begins work on AIRSS. Recent programs that Northrop Grumman has worked on in this area include serving as a subcontractor on SBIRS High and as the prime contractor on the Missile Defense Agency’s Space Tracking and Surveillance System and the Defense Support Program missile warning satellites that are on orbit today, he said in a Dec. 7 interview.

Patricia Oleson, vice president for space systems at General Dynamics Advanced Information Systems, said in a Dec. 8 news release that the company plans to bring “an innovative and responsive” approach to the program.