The Air Force completed the system design review (SDR) of the Transformational Satellite Communications System (TSAT).

That paves the way for selection of the TSAT space-segment contractor before the end of the year, the Space and Missile System Center (SMC) announced.

The four-week review, SMC said, represents the culmination of over three years of design work on the TSAT. Its purpose was to validate that there is an appropriately mature technical baseline present and that a feasible preliminary design approach has been established to warrant moving the TSAT program ahead.

“SDR completion marks a very significant milestone in this important phase of the program,” Brig. Gen. Ellen Pawlikowski, commander of the SMC Military Satellite Communications Systems Wing, said in a statement. “It recognizes a considerable achievement from years of work by the government and industry to deliver leading-edge communications capability to our warfighters.”

The SDR, which was led by the wing TSAT program office, was held in multiple locations in Los Angeles, the home of SMC, as well as in San Jose, and Sunnyvale, Calif., the center said. Hundreds of industry representatives and government reviewers from across the Department of Defense participated.

TSAT is expected to reach initial operational capability in 2018, with launch of the first satellite planned in the fiscal year ending Sept. 30, 2016.

The Boeing Co. [BA] and Lockheed Martin Corp. [LMT] lead teams currently under contract with the Air Force to define the TSAT satellites, ground gateways and satellite command and control components. SMC intends to choose one of them late this year to proceed into the TSAT space segment’s system development and demonstration phase and begin to build the satellites.

SMC chose Lockheed Martin in February 2006 to develop the related TSAT Mission Operations System (TMOS) segment that will provide network-centric interoperability between TSAT and the GIG.