Uncertainty over satellite constellation means alt-GPS capability up in the air: Official

AFA 2025 — The Space Development Agency’s (SDA) plans to provide US military operators with positioning, navigation and timing (PNT) signals in situations where GPS is unavailable now are up in the air — as the Space Force reconsiders pushing forward with the agency’s next set Transport Layer data relay satellites.

SDA Director Gurpartap “GP” Sandhoo told reporters Monday that the agency’s Proliferated Warfighter Space Architecture (PWSA) of communications and missile tracking satellites in low Earth orbit will have “organic” PNT capability to ensure the constellations themselves can operate “in case GPS is denied” by adversary jamming.

But there’s a question as to whether SDA will be able to transmit those alternate PNT signals to warfighters on the ground if the Tranche 3 Transport Layer is cancelled, Sandhoo said.

“I don’t have an answer for that,” he during the annual Air and Space Forces Association conference at National Harbor, Md.

SDA originally planned to buy 140 T3 Transport Layer satellites in three different configurations to provide worldwide routing of high volumes of data with low latency, with launching to begin in 2028. SDA in January put out a draft solicitation for 40 of the first variant, called Upsilon, asking for industry responses by Feb. 10.

With regard to PNT, the agency’s planned Navigation Layer would be based on using the laser links among the PWSA satellites, by “leveraging two-way time transfer (TWTT) and ranging” provided, according to an SDA post on LinkedIn. It would have three purposes: maintaining “continuity of operations” for SDA’s satellites, pinpointing GPS jamming and providing that data to Space Force operators, and providing “space-based PNT Services” through a dedicated signal, the agency explained.

The SDA Warfighter Council last August approved the inclusion in Tranche 3 of the “Light Weight Service” developed by the Air Force Research Laboratory to provide the alternate PNT signal, according to the abstract of a paper co-authored by two agency officials among others and submitted to the Institute of Navigation for its upcoming June conference.

The laboratory did not respond to a inquiry from Breaking Defense about the concept.

However, as part of the budget drill for fiscal 2026, the Department of the Air Force and the Space Force now are in the midst of an analysis of whether to replace the T3 birds by buying commercial services from SpaceX’s Starshield network under a mysterious program called MILNET.

The service put $277 million in its first public budget request in FY26 budget request, although there have been multiple reports from Space Force and congressional officials that the program already is underway.