U.S. Co-Orbital Anti-satellite Testing Fact Sheet

This fact sheet reviews U.S. historical experimentation and existing space technology capabilities relevant to co-orbital ASAT (anti-satellite) systems, despite the absence of an acknowledged operational counterspace program. It outlines past tests and current technical capacity that could, if reoriented, support future co-orbital ASAT development and broader space security objectives.

Key topics include:

Project SAINT (1960–1962): An early USAF “satellite inspector” project that aimed to develop close-approach vehicles—potentially with onboard kill mechanisms—but was cancelled before launch due to budget and political constraints, highlighting early developments in space technology and counterspace concepts.

Delta 180 Experiment (1986): The only confirmed U.S. co-orbital intercept test, part of the Strategic Defense Initiative (SDI). A modified Delta 2 launch vehicle successfully intercepted a target in low Earth orbit at 3 km/s. The test created orbital debris, though all fragments reentered within seven months, illustrating early challenges in space debris management and space security.

RPO Missions and Tech Tests:
Prowler (1990): Conducted undetected rendezvous and proximity operations (RPO) in GEO, contributing to space situational awareness capabilities.
XSS-11 (2006): Demonstrated close approach and inspection in LEO, advancing space technology and on-orbit capabilities.
GSSAP satellites (active): Perform close inspections and space situational awareness in GEO, supporting ongoing space security operations.

Golden Dome Missile Defense Initiative (2025): Launched by executive order, the program envisions a space-based interceptor layer. Although intended for missile defense, such systems could also enable a latent co-orbital ASAT capability, depending on design, space policy, and governance decisions.

The fact sheet emphasizes that while the U.S. does not currently deploy or acknowledge co-orbital ASAT systems, its technical readiness—from space situational awareness infrastructure to proximity operations—would allow it to develop and field such counterspace capabilities relatively quickly if desired.

See page 2 for technical details of the Delta 180 test and the planned architecture of Golden Dome. A timeline of known or suspected co-orbital ASAT-related activity is included at the bottom of page 2.