Newsletters
In a discovery that challenges expectations about decommissioned satellites, astronomers have detected a powerful radio pulse lasting just 30 nanoseconds from NASA’s long-defunct Relay 2 spacecraft.
The burst, observed by the Australian Square Kilometre Array Pathfinder (ASKAP), may have resulted from either an electrostatic discharge or a micrometeoroid impact, opening up new possibilities for studying space weather and orbital hazards remotely.
On 13 June 2024, at precisely 5:13 a.m. UTC, ASKAP's advanced detection system captured a nanosecond-duration radio pulse within the 695.5 to 1031.5 MHz frequency range.
Initially appearing similar to a fast radio burst (FRB), the signal's characteristics—particularly its lack of dispersion—led researchers to trace its origin to a near-Earth source rather than deep space.
The signal’s duration of less than 30 nanoseconds and extraordinary brightness—estimated at over 300 kilojanskys—ruled out most known natural causes. Advanced processing revealed the signal came from a point approximately 4500 kilometers from the array, consistent with a satellite in low-Earth orbit.
Further analysis pinpointed the source as Relay 2, a NASA telecommunications satellite launched in 1964 and decommissioned in 1965. Despite being inoperative for nearly 60 years, the satellite was located within 3.2 arcminutes of the burst’s sky position and at a matching altitude at the time of detection.
Relay 2 once served as a communication test platform and carried scientific instruments, including radiation detectors. Its orbit intersects the inner Van Allen radiation belt, making it a potential site for charge build-up despite its inactive status.
The leading theory attributes the pulse to an electrostatic discharge (ESD), a phenomenon caused by the accumulation and sudden release of electric charge on spacecraft surfaces.
Such events are known to produce short-lived radio emissions and can damage satellites. While usually difficult to monitor directly, the ASKAP observation demonstrates that ground-based radio telescopes can detect these discharges remotely.
Earlier detections using the Arecibo Observatory had revealed similar signals from GPS satellites, but on timescales 1000 times longer. Relay 2’s older design and potentially higher charge retention capacity may explain the shorter, more intense discharge.
An alternative explanation suggests the burst was caused by a micrometeoroid impact. Such collisions produce plasma clouds and could trigger high-frequency radio emissions through rapid discharges across newly formed cracks.
Simulations and laboratory tests have shown that nanosecond-scale pulses are plausible under these conditions.
Statistical estimates, however, indicate a low likelihood of such impacts during the period in which Relay 2 was observed. This, combined with the burst’s similarity to known ESD signals, tilts the balance in favor of the electrostatic discharge hypothesis.
The finding carries significant implications for both astrophysics and satellite monitoring.
Nanosecond-duration radio pulses are commonly sought by experiments studying high-energy cosmic particles, and signals like the one from Relay 2 could mimic these events, leading to false positives.
At the same time, this detection proves that ground-based radio observatories can identify sudden electrical discharges in space, offering a new method for monitoring spacecraft integrity and potential orbital threats.
Retrofitting existing fast radio burst (FRB) monitoring systems or developing new instruments could enhance our ability to study these phenomena.
1 min read
3 min read
