The European Space Agency (ESA) has successfully re-established communication with the Jupiter Icy Moons Explorer (Juice) spacecraft after a mysterious anomaly was traced back to a bug in its code. The probe, launched in April 2023, had fallen silent on July 16, prompting concerns about a possible major failure.
However, further investigation revealed that the problem lay not with the ground station or antenna equipment, but rather with the software itself. The timer used by the software was set to restart every six months, which caused the signal amplifier to remain switched off at times, making it undetectable from Earth.
To resolve the issue, ESA engineers attempted to send commands blindly into space, hoping that a backup antenna might receive them. After several attempts, they successfully re-established contact by switching on the signal amplifier. The spacecraft was found to be healthy, but the question of what happened remained until software engineers discovered the root cause.
“We need additional logic on-board to avoid radiation of the downlink through forbidden zones,” explained Angela Dietz, Juice Spacecraft Operations Manager. “Possible mitigations include regular controlled resets or replacing the timer with one that wraps around only after 100 years.”
Fortunately, there are 15 months until the timer’s next wraparound, by which time Juice will have completed its next flyby of Earth on its trajectory to Jupiter.
Source: https://www.theregister.com/2025/08/26/juice_communications_bug