The Pentagon has spent years hunting hypersonic glide vehicles. Its tracking agency now says the current sensor generation is not built to hold them, and is asking industry what comes next.
What the solicitation asks for
The Space Development Agency issued a request for information on October 20, gathering concepts for Tracking Layer Tranche 4 and evaluating shorter on-orbit demonstrations to run ahead of it. Responses are due December 4.
The agency wants payloads that maintain custody of targets across a full flight trajectory, not just during the boost phase that earlier tranches emphasized. Infrared and electro-optical sensors would hand their tracks through optical inter-satellite links into the Transport Layer mesh, so fire-control data reaches tactical units quickly.
Production contracts plus experiments
SDA is weighing two tracks in parallel: conventional production awards for Tranche 4 satellites, and separate partnership deals for rapid prototyping and short flight demonstrations. Testing experimental payloads on dedicated platforms lets the agency retire technical risk before it buys a constellation.
The lineage is expensive. Officials awarded $3.5B for Tranche 3 tracking satellites in late 2025, then added $1.75B in July for 36 accelerated missile defense spacecraft.
The data route is the vulnerability
A sensor that cannot pass its track is a telescope. Routing fire-control quality data through a laser-linked mesh creates a network whose scheduling logic, crosslinks and ground entry points all sit inside the kill chain rather than beside it.
An adversary that degrades a link does not need to blind a satellite. It only needs the track to arrive late.
This round of requests will shape both the formal Tranche 4 solicitation and the operational parameters of the constellation that follows.
