The U.S. Space Force has cleared a major design hurdle in its Resilient Missile Warning and Tracking program, completing the preliminary design review for the 10-satellite Epoch 2 medium Earth orbit constellation.

Space Systems Command announced Sunday that System Delta 84, working with prime contractor BAE Systems Space and Mission Systems, achieved the milestone nine months after the contract award. The critical design review is scheduled for this summer.

Space Systems Command awarded BAE Systems Space and Mission Systems a $1.2 billion firm-fixed-price other transaction authority contract for Epoch 2 in May 2025, the command said. First delivery is planned for fiscal year 2029, according to Space Systems Command.

“This milestone was achieved by a talented and dedicated team working in close collaboration,” 1st Lt. Sabrina Taylor, SYD 84 Epoch 2 chief systems engineer, said in a statement. “Using advanced digital tools allowed us to ensure the design is sound and ready for the next phase. … Collectively, we are demonstrating we can move quickly while maintaining technical excellence.”

Epoch 2 follows Epoch 1, a 12-satellite constellation being built by Millennium Space Systems, according to SpaceNews. The program is designed to provide persistent tracking of advanced missile threats.

“Our team is delivering to outpace the threat,” Lt. Col. Brandon Castillo, SYD 84 Epoch 2 system program manager, said in a statement. “This expanded constellation will provide the global coverage needed to protect our Nation, service members, Allies, and partners from the most advanced missiles.”