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WASHINGTON — A SpaceX Falcon 9 rocket on July 16 launched 21 satellites for the Space Force’s Space Development Agency, restarting deployment of the Pentagon’s first operational low Earth orbit military data network after a months-long pause.
The mission, designated T1TL-E, lifted off at 4:32 p.m. Eastern from Vandenberg Space Force Base in California. The satellites, built by York Space Systems, are the third batch of Tranche 1 Transport Layer spacecraft for SDA’s Proliferated Warfighter Space Architecture, or PWSA, and York’s second production lot for the tranche.
The launch marks a restart for one of the Space Force’s most closely watched satellite programs. SDA’s previous Tranche 1 launches placed 21 York satellites in orbit in September 2025 and 21 Lockheed Martin satellites in October 2025. With the latest mission, SDA will have 63 Tranche 1 Transport Layer satellites on orbit, half of the planned 126-satellite Transport Layer for Tranche 1.
The Transport Layer is the communications backbone of the PWSA, SDA’s planned network of low Earth orbit satellites designed to support missile warning, missile tracking and military data relay. The layer is intended to move data across space through optical intersatellite links and deliver it to ground systems, ships, aircraft and other military users.
SDA Director Gurpartap “GP” Sandhoo told reporters ahead of the launch that the pause was driven by hardware and software issues found on the first 42 Tranche 1 satellites. Those problems included thermal-modeling issues, delays making contact with ground entry points, and propulsion and orbit-raising challenges.
The gap between launches reflects a shift in how SDA is managing the constellation. The agency once envisioned a cadence of roughly monthly satellite launches. Sandhoo said SDA is now moving to a readiness-based model, launching “whoever is ready” rather than holding to a fixed schedule.
That means launch availability is no longer the main pacing item. Instead, SDA is coordinating launches around spacecraft checkout, assembly, integration and test readiness.
“By the end of this launch, we’ll have half our transport constellation on orbit,” Sandhoo said, adding that with three planes deployed, SDA can begin discussing “real capability for the warfighter.”
The architecture remains in an early stage, however. Sandhoo said SDA has not yet established the mesh network that would allow the satellites to route data across the constellation. The agency plans to first build optical links within each orbital plane before attempting links between planes, a step Sandhoo said gets “very complicated very quickly.”
“We have not established a mesh yet, but we are working our way towards it,” he said.