A Ghost Signal From Orbit
Astronomers in Australia have picked up an unexpected and powerful burst of radio waves that initially appeared to come from deep space — only to trace it back to a long-dead NASA satellite drifting silently overhead. The discovery, made using the ASKAP radio telescope in Western Australia, has reignited debate about how decommissioned spacecraft and orbital debris could increasingly interfere with one of the most sensitive branches of modern astronomy. Researchers from Curtin University and the international Commensal Real-time ASKAP Fast-Transients (CRAFT) collaboration reported the finding in a peer-reviewed paper, identifying the source as Relay 2, a communications satellite launched by NASA in 1964 and inactive since 1967.
What the Telescope Saw
The signal, lasting less than 30 nanoseconds, was so brief and intense that it briefly outshone every other radio source in the sky. Initially, the team suspected it might be a fast radio burst (FRB) — a class of millisecond-scale extragalactic flashes whose origins remain among the most contested mysteries in contemporary astrophysics. But when researchers calculated the source direction and distance, they realized the pulse had originated just a few thousand kilometres above Earth, not billions of light-years away.
Lead author Dr. Clancy James of the Curtin Institute of Radio Astronomy told reporters the team was “stunned” to discover the culprit was an aging NASA relay satellite. According to a report published by The Guardian, the researchers narrowed down two possible explanations: an electrostatic discharge — essentially a spark caused by accumulated charge on the satellite’s metal surface — or a micrometeoroid strike vaporising into a brief plasma cloud. Both processes can release radio emissions, though detecting one at such fine temporal resolution is unprecedented.
Background: Why Relay 2 Matters
Relay 2 was a small, drum-shaped spacecraft built to test global communication relays during the early space age. It carried transponders for transmitting telephone, television, and data signals, and was part of a NASA program that helped lay the groundwork for today’s commercial satellite networks. After its onboard transponders failed in 1967, it was abandoned in orbit, where it has been quietly circling Earth ever since — one of thousands of dead spacecraft now classified as space debris by the European Space Agency.
The detection of a sharp radio pulse from such an old object is significant because it suggests that decommissioned satellites can still produce transient electromagnetic signatures that mimic genuine astrophysical phenomena. With FRB studies relying on extremely sensitive instruments, even a fleeting signal from low Earth orbit can corrupt observations or create false positives.
Implications for Astronomy and Orbital Safety
The finding arrives at a delicate moment for radio astronomy. Mega-constellations such as SpaceX’s Starlink and Amazon’s Project Kuiper are placing tens of thousands of satellites in orbit, and astronomers have repeatedly raised concerns about radio frequency interference. The Curtin team argues that detecting nanosecond-scale electrostatic discharges from defunct satellites could become a new diagnostic tool — both for monitoring spacecraft health and for tracking debris that is otherwise too small to image directly.
Dr. James suggested the technique might one day allow ground-based radio telescopes to act as a kind of early-warning system for satellite degradation, identifying objects building up dangerous charges before they fail catastrophically. That has practical relevance for satellite operators, since electrostatic events can damage active spacecraft and contribute to in-orbit breakups.
What Comes Next
Researchers plan to comb through archival ASKAP data to determine how often similar pulses have been recorded — and whether some previously catalogued “events” might actually have been satellites, not stars. With the Square Kilometre Array under construction in Australia and South Africa, sensitivity will only increase, raising both the promise of new discoveries and the risk of more orbital false alarms. For now, Relay 2 has offered an unexpected reminder that the sky humans have filled with hardware can still surprise the scientists looking up at it.
