A nanosecond-duration radio pulse originating from the defunct Relay 2 satellite

TL;DR

This paper reports the detection of a nanosecond radio burst from the decommissioned Relay 2 satellite, suggesting electrostatic discharge or plasma discharge as possible causes, with implications for spacecraft safety and astrophysical observations.

Contribution

First detection of a nanosecond radio pulse from a defunct satellite, linking satellite discharges to transient radio signals and highlighting new remote sensing opportunities.

Findings

Detected a <30 ns radio burst from Relay 2 satellite.

Identified potential electrostatic or plasma discharge origin.

Implications for spacecraft safety and transient radio observations.

Abstract

We report the detection of a burst of emission over a 695.5 MHz-1031.5 MHz bandwidth by the Australian Square Kilometre Array Pathfinder, ASKAP. The burst was localised through analysis of near-field time delays to the long-decommissioned Relay 2 satellite, and exhibited a dispersion measure of $2.26 \cdot 10^{-5}$ pc cm$^{-3}$ -- 69.7 TECU, consistent with expectations for a single pass through the ionosphere. After coherent dedispersion, the burst was determined to be less than 30 ns in width, with an average flux density of at least 300 kJy. We consider an electrostatic discharge (ESD) or plasma discharge following a micrometeoroid impact to be plausible explanations for the burst. ESDs have previously been observed with the Arecibo radio telescope, but on 1000 times longer timescales. Our observation opens new possibilities for the remote sensing of ESD, which poses a serious threat to spacecraft, and reveals a new source of false events for observations of astrophysical transients.