JUICE loses contact for 20 hours before Venus flyby; team fixes timer bug with blind commands

European Space Agency/JUICE (Jupiter Icy Moons Explorer)

Six weeks before its Venus flyby, JUICE stopped sending telemetry. Engineers traced it to an internal timer that resets every 16 months and, if hit at the wrong moment, leaves the radio amplifier off. Blind commands sent across 200 million km switched it back on, and the probe was healthy and kept its schedule.

• Contact lost on 16 Jul 2025 during a routine ground-station pass
• Cause: a timer that restarts every 16 months left the signal amplifier switched off
• Recovered after nearly 20 hours with commands sent without telemetry
• Venus flyby went ahead on 31 Aug 2025 as planned