USSF-124

HBTSS and the SDA Tranche 0 Tracking Layer satellites together form part of the Space Development Agency's low-orbit missile-warning architecture. The four T0TR satellites (Raptor 1-4) carry wide field-of-view infrared sensors for persistent hypersonic tracking; the two HBTSS satellites - one built by L3Harris, one by Northrop Grumman - extend that to high-fidelity tracking and interceptor handoff for missile-defense engagements.

This mission was part of a Phase 2 US Space Force contract awarded in 2022.