Galileo’s Antenna Failure, and the Mission That Continued

Transcript

On 11 April 1991, Galileo suffered a serious communications failure: its high-gain antenna did not fully deploy. That antenna was meant to provide the primary high-rate link, and without it, controllers feared they could not transmit data from the upcoming encounter with asteroid 951 Gaspra. Galileo still had a low-gain antenna, so the mission shifted to that backup for the remainder of its operations. The trade was speed. Engineers answered with data-compression software, allowing more information to pass through the weaker link than would otherwise have been possible. The result was not a canceled mission, but a constrained one. On 29 October 1991, Galileo flew past 951 Gaspra at a distance of 1,604 kilometers, becoming the first human-made object to encounter an asteroid. Even with the damaged communications system, the spacecraft returned substantial results, including 150 images. Galileo’s antenna failure is therefore a lesson in mission resilience: redundant hardware preserved a path forward, and software recovered part of the lost capability.