Overview

• Relay2, launched by NASA in January 1964 and inactive since 1967, unexpectedly transmitted a primary 10-nanosecond energy pulse followed by weaker emissions totaling about 30 nanoseconds.
• The Australian Square Kilometre Array Pathfinder telescope detected the summer 2025 burst and confirmed its origin by matching timing and orbital data to Relay2.
• Investigators favor an electrostatic discharge caused by accumulated space plasma on the long-dormant satellite as the leading explanation.
• A secondary hypothesis holds that a micrometeorite impact generated a plasma cloud that could have prompted the transient signal.
• The observation suggests a novel technique for remotely monitoring electrostatic events on derelict satellites to better assess collision and discharge hazards for operational spacecraft.