In 2024, a U.S. government official warned that Russia could be developing a satellite designed to carry nuclear weapons into space — a claim that followed the 2022 launch of a suspicious Russian satellite into low-Earth orbit just weeks before the invasion of Ukraine. A nuclear detonation in low-Earth orbit would release trillions of highly energetic electrons capable of destroying many of the satellites that keep telecommunications, GPS, and space-based internet running.

The 1967 Outer Space Treaty bans placing nuclear weapons in space, but there is currently no way to verify that a satellite doesn’t contain one — no verification method has even been proposed in unclassified, peer-reviewed literature. Now, MIT Professor Areg Danagoulian is proposing one. In a new paper published in Nature, Danagoulian describes a satellite-based sensor system that could orbit near a suspect satellite and detect neutrons generated when high-energy protons collide with radioactive material.

Danagoulian calculates that a sensor system the size of a large encyclopedia could detect a nuclear weapon with 99 percent accuracy if it orbited within 4,000 meters of a suspect satellite for about a week — and that detection time could shrink to a matter of hours with multiple sensor satellites, or if a single sensor got within 1,000 meters.

“If we eventually have some verification mechanisms for the Outer Space Treaty, that will put pressure on countries to respect the treaty or disclose what they are doing, because they know if they try to violate it, we will find out. I very much hope this will turn into a real system, or proof-of-concept system, but the goal right now is to get national labs to use this work for their own research, and to get policymakers to seriously consider this technology as a potential part of national technical means.”

Areg Danagoulian, MIT

A Lesson From 1962

The danger isn’t hypothetical. In 1962, the U.S. detonated a 1.4-megaton thermonuclear warhead in space, unintentionally destroying many of the era’s early satellites when the blast’s freed electrons became trapped in Earth’s Van Allen radiation belt.

“When you have a nuclear detonation in outer space, basically the whole body of the bomb becomes ionized, and nearly every single electron in the weapon’s mass becomes free. It gets injected into what’s called the inner Van Allen radiation belt. Once there, the electrons start hitting everything flying through those belts, causing ionization, radiation damage, and more.”

Areg Danagoulian

Concerns have sharpened since Russia’s 2022 launch of Cosmos 2553, a satellite Russia says is used for surveillance and sensing but which U.S. authorities believe may carry components of a nuclear device undergoing testing. A detonation at that orbit could destroy U.S. reconnaissance satellites, international communications platforms, and Starlink satellites alike.

“The Russians launched this satellite in a very strange and unusual orbit because it goes through the most hostile environment possible around the planet. No one puts satellites there because it’s highly radioactive. Why would you put a satellite in that orbit? Well, that location is likely the best point for trapping electrons if you were to detonate a thermonuclear weapon.”

Areg Danagoulian

Reading Neutrons From Orbit

The detection method relies on spallation: when an energetic proton slams into a high-atomic-number element like uranium or plutonium, it can knock loose roughly 40 neutrons. Danagoulian’s design uses two panels of neutron-sensing scintillators sandwiched between synthetic diamond detectors that can distinguish neutrons coming from radioactive material from the naturally occurring protons and electrons that bombard every satellite in low-Earth orbit.

“Most neutron detectors are very sensitive to protons, so you have to come up with some smart ways to reject protons but keep neutrons. You also have to tell the difference between naturally occurring neutrons and neutron spallation from the satellite.”

Areg Danagoulian

Danagoulian describes the paper as a feasibility study rather than a finished system, and is working with researchers in MIT’s Center for Nuclear Security and Policy to understand the policy landscape around it. He believes that if a version of the system is eventually built, it could strengthen trust between adversarial nations by grounding compliance claims in physical evidence rather than assertions.

“You can fake intelligence, but you can’t fake physics.”

Areg Danagoulian

The work was supported in part by the National Nuclear Security Administration, the Carnegie Foundation for the Advancement of Teaching, and Longview Philanthropy.

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The study, “Verification of the Outer Space Treaty with cosmic protons,” was published in Nature (DOI: 10.1038/s41586-026-10783-2).