WASHINGTON — The Space Development Agency on June 28 released a final request for proposals for its next procurement of 100 satellites as the agency continues to build out a military constellation in low Earth orbit.

These 100 satellites, named Alpha, will be part of a mesh network known as Transport Layer Tranche 2.

The Transport Layer Tranche 2 also includes 72 Beta satellites for which SDA already has requested bids

The procurement of 100 Alpha satellites will be split between two vendors. SDA issued a draft solicitation in May. The final proposals are due July 28.

Each Alpha satellite will have at least three, or up to four optical communications terminals, a Ka-band and a Link 16 payload. These satellites also will be equipped with on-board command-and-control data processors and autonomous navigation payloads.

Transport Layer Tranche 2 “will provide global communications access and deliver persistent regional encrypted connectivity in support of warfighter missions around the globe,” said SDA.

SDA, an organization under the U.S. Space Force, is building a layered network of military satellites. The Transport Layer will serve as a tactical network to move data to users around the world, communicating classified data such as early warnings of missile launches.

The overall constellation, which SDA calls the proliferated warfighter space architecture, includes a Transport Layer of interconnected communications satellites and a Tracking Layer of missile-detection and warning sensor satellites. 

Transport Layer Tranche 2 to launch in 2026

The agency already has acquired satellites for Tranche 0 and Tranche 1 of the Transport Layer and the Tracking Layer. The first launch of Tranche 0 satellites took place in April and a second Tranche 0 launch is targeted for late July. Tranche 1 is projected to launch in 2024 and Tranche 2 in 2026.

The proliferated constellation is made up of small satellites supplied by multiple vendors, all interconnected via optical laser links.

The Transport Layer Tranche 2 will be SDA’s largest procurement to date. 

SDA said Tranche 2, when deployed, will add enough nodes to the network to provide global coverage for U.S. military users. 

Sandra Erwin writes about military space programs, policy, technology and the industry that supports this sector. She has covered the military, the Pentagon, Congress and the defense industry for nearly two decades as editor of NDIA’s National Defense...