ESA's Jupiter Icy Moons Explorer, Juice, performed a gravity assist at Earth on September 28, passing just 8,640 km above the Indian Ocean. The maneuver altered the spacecraft's trajectory by 20 degrees and boosted its velocity by 3.5 km/s, setting it on a more direct path toward Jupiter while using only a small amount of propellant. Mission controllers had reserved six course-correction opportunities before the flyby but needed just one to achieve the precise approach.
The encounter was not only about navigation. With Earth and the Moon as targets, Juice's ten science instruments had a rare chance to be calibrated under known conditions. Teams prioritized activities based on their relevance to future observations of Jupiter's icy moons, and the spacecraft also spent several days measuring Earth's magnetotail. Those data can be combined with observations from the European-Chinese Smile mission to link distant magnetic-tail activity with auroral events near Earth.
Juice will make one more Earth flyby in January 2029, which is expected to put it on the final trajectory to reach Jupiter in 2031. The upcoming flybys of Ganymede, Callisto, and Europa will be far more demanding, making the current rehearsal and fuel savings especially valuable for the mission's scientific campaign.