Study Findings: Verification of the Outer Space Treaty with Cosmic Protons

Nature abstract of study findings:

The Outer Space Treaty (OST) was opened to signatures in 1967 and, since then, 117 countries, including China, the USA and Russia, have become part of it. Among other stipulations, the treaty bans the placement of nuclear weapons in outer space. Recently, the US government has raised worries that Russia is testing nuclear-armed anti-satellite weapon (ASAT) components, with the possibility that it will place a nuclear weapon in space. Such a device, if detonated, would destroy most of the satellites in the low Earth orbit. This danger is compounded by the lack of a verification mechanism for the OST. No methodologies of verification have been proposed in the open peer-reviewed literature. Here a concept and feasibility study is presented for verifying a satellite’s compliance to the OST by observing the neutrons induced by spallation from the approximately GeV protons in the inner Van Allen radiation belts. The calculations show that a 9U-CubeSat-sized detection platform can identify a thermonuclear weapon from a distance of 4 km in approximately one week of observation. This conceptual study will stimulate and inform future research and development of verification platforms for the OST.

Citation: Danagoulian, A. Verification of the Outer Space Treaty with cosmic protons. Nature 655, 585–590 (2026).

DOI: https://doi.org/10.1038/s41586-026-10783-2

Study-related stories:

Nuclear Newswire – “MIT Professor Develops Method to Verify Compliance with Outer Space Treaty”

Science News – “Nature Study Identifies a New Way to Spot Nuclear Weapons in Orbit”

Discover Magazine – “Proposed Satellite Detector Could Identify Nuclear Weapons in Orbit With More Than 99 Percent Confidence”