Small satellites would detect nuclear arms launched secretly into orbit under a new monitoring system proposed by a scientist to address fears about the militarisation of space.
The probes would look for tell-tale emissions of subatomic particles that show spacecraft are carrying such weapons in breach of international law and with the potential to wreak havoc on thousands of satellites orbiting Earth.
The threat of off-planet conflict has grown as powerful countries jostle for supremacy in outer space and rely ever more heavily on it for essential services such as communications and navigation.
A surveillance mechanism for nuclear threats could be a vital deterrent to both the deployment of the weapons and the escalation of crises between mutually distrustful nations, said Areg Danagoulian, research author.
“As launches intensify and space becomes more populated, ambiguity becomes dangerous,” said Danagoulian, associate professor of nuclear science and engineering at the Massachusetts Institute of Technology.
“If one state suspects another of placing a nuclear weapon in orbit, the absence of a verification mechanism makes the crisis harder to manage. If a bad-faith actor knows that their attempt will be discovered via inspection, they will be more likely to decide it's not worth pursuing.”
The proposed weapons-spotting satellite could weigh less than 100kg and be made from commercially available equipment, the researcher said. It would work by detecting neutron particles given off from the interaction between the nuclear device’s uranium and protons trapped in Earth’s magnetic field, the researcher said.
The monitoring spacecraft, known as a CubeSat, would need to make about a week of measurements at a distance of 4km, according to a paper published in Nature on Wednesday.
The approach should be politically feasible because it was “fundamentally passive” and did not involve X-raying or irradiating the satellite being analysed, Danagoulian said.
It could be valuable because there is no technical mechanism to ensure compliance with the 1967 Outer Space Treaty, which bans putting nuclear arms into orbit and is signed by leading space nations.
Danagoulian said he had shared the paper with many colleagues from national laboratories and defence research institutions and had generally received “strong encouragement” to continue his work.
“At the same time I was told that while they have done quite a bit of work internally in the classified domain, they cannot share any information due to very strict levels of secrecy,” he said.
Concerns about potential breaches of the treaty have grown because of US intelligence claims that Russia has been developing a space-based anti-satellite nuclear weapon.
Russia’s President Vladimir Putin has said Moscow is “categorically against the deployment of nuclear weapons in space”, although he added that it would “have to think about what strategic stability is” if the west tried to inflict a strategic defeat on it.
The Outer Space Treaty came after a 1962 US test, known as Starfish Prime, showed the potential devastation caused by nuclear explosions in space. The test, carried out 400km above the Pacific Ocean, damaged or destroyed an estimated one-third of the satellites then in low Earth orbit.
The electromagnetic pulse from the blast reached the planet’s surface and caused disruption to telephones and power systems, including street-light failures in Hawaii.
The mooted monitoring method for nuclear weapons could be a useful tool after further improvement and testing, said Angela Di Fulvio, an associate professor at the University of Illinois Urbana-Champaign.
It would need technical refinements and proof it could perform in “less idealised conditions”, including if there were other non-nuclear weapon neutron signals or if suspect satellites tried to evade detection.
The weapon monitoring might complement so-called “deterrence-by-denial” improvements to satellite security, in which craft use defences such as physical manoeuvres or anti-jamming technology to curb the impact of attacks on them, Di Fulvio added.
“Verification addresses the problem from a different direction,” she said in a commentary also published in Nature. “It could increase the chance that a satellite with prohibited capability is identified before it can be used, reducing the value of secretly placing such a system in orbit.