A study published in Nature Astronomy proposes the first peer-reviewed technique for detecting thermonuclear warheads in orbit, addressing a verification gap in the 1967 Outer Space Treaty that 118 nations have signed. MIT nuclear physicist Areg Danagoulian designed a detection method using radiation naturally trapped in Earth's inner Van Allen belt to identify fissile material through spallation, a nuclear signature. The work gained urgency after U.S. intelligence alleged Russia tested an anti-satellite orbital nuclear weapon in 2024, though Russia has denied the claim.
Danagoulian's concept uses a 9U CubeSat equipped with a neutron detector that could confirm a warhead's presence within a week at 4 kilometers distance, shrinking to one hour at 1 kilometer -- or 15 hours with a constellation of ten satellites. The approach works only in the inner Van Allen belt around 2,000 kilometers altitude, limiting its scope as a universal detection method. Experts stress the technique would be most viable as part of a cooperative treaty verification regime rather than unilateral inspections, which could escalate tensions. Danagoulian plans to collaborate with national laboratories on a proof-of-concept prototype, though peer reviewers note the work remains a simulation requiring real-world validation. A remaining challenge involves distinguishing offline nuclear reactors from weapons, which the team is still working to resolve.