On Oct. 18, 1989, the Galileo spacecraft launched aboard Space Shuttle Atlantis, the first step in its journey to Jupiter. Although the original plan for Galileo had been a direct path to the gas giant, the booster that would have powered that journey was canceled after the Challenger disaster, due to safety concerns. A new plan was necessary: Instead, three planetary gravity assists would be used to put Galileo on the right trajectory. The first, a flyby of Venus, was completed successfully on Feb. 10, 1990.
On Dec. 8, 1990, Galileo made its first flyby of Earth, slingshotting by at a distance of 597 miles (960 kilometers). The gravity assist was successful, increasing the craft’s speed and sending it off on an orbit around the Sun before its second Earth flyby, exactly two years later. The three combined gravity assists were enough to send Galileo off to Jupiter, where it arrived on Dec. 7, 1995. It would spend the next eight years there – the first spacecraft to orbit an outer planet – collecting data on the gas giant, its rings, and five of its moons.
