A nanosecond-duration radio burst generated by a defunct satellite

Astronomy -and in particular the study of transient sources -is increasingly affected by spacecraft-borne interference.This can originate due to both intentional and unintentional transmission, but little is known about the properties of satellite-borne interference at very short (sub-millisecond) timescales.Here, we report the detection of an intense burst of radio emission on 2024 June 13 th 05:13:09.035UTC, over a 695.5 MHz-1031.5MHz bandwidth by the Commensal Realtime ASKAP Fast Transients Survey (CRAFT) coherent detection system, CRACO, on the Australian Square Kilometre Array Pathfinder, ASKAP.We find that the observed burst dispersion measure of 2.26 10 -5 pc cm -3 (69.7 TECU), rotation measure of 1.5 rad m -2 , arrival direction, and reconstructed near-field distance of 4500 80 km are all consistent with the burst arriving from the Relay 2 satellite, which was decommissioned over 50 years ago.