ESA's Juice spacecraft swings past Earth, gaining speed on its way to Jupiter

The European Space Agency's Juice spacecraft flew past Earth on September 28, 2026, using the planet's gravity to adjust its course toward Jupiter. ESA said the flyby went as planned and improved the probe's trajectory.

The flyby

Juice made its closest approach at 13:45 CEST, or 11:45 UTC, passing 8,640 km above the Indian Ocean, according to ESA. In its preview of the maneuver, the agency said the spacecraft would pass over Australia from northeast to northwest 15 to 30 minutes before closest approach.

ESA says the encounter deflected Juice's path by 20 degrees from its pre-flyby course and increased its speed by 3.5 km/s. Gravity assists like this change a spacecraft's course without using much of its own fuel, which ESA says leaves more propellant for later observations of Jupiter's icy moons.

"The flyby required ultra-precise navigation in real time. Thanks to our very careful planning, we used only a small amount of the propellant reserved for this flyby," said Angela Dietz, Juice's spacecraft operations manager, in ESA's report on the flyby.

Before the encounter, the team carried out a trajectory correction maneuver over a four-week navigation campaign. Dietz described that maneuver to ESA: "It was of relatively small size, but extremely effective."

Science along the way

ESA planned to switch on all 10 of Juice's science instruments between September 23 and October 3 to calibrate them and prepare for data analysis. During the flyby, the spacecraft tested its instruments and took images of Earth, the Moon and Madagascar, according to ESA.

Juice also measured magnetic fields and charged particles in Earth's magnetotail and coordinated those observations with ESA's Smile mission. The navigation camera was used to test an optical navigation technique by imaging the lunar horizon, ESA said.

The road to Jupiter

Juice launched from French Guiana in April 2023. In 2024 it made the first-ever combined lunar-Earth flyby, and it later flew past Venus, according to ESA. The September 2026 encounter was its third gravity assist. ESA also noted that the spacecraft observed Comet 3I/ATLAS in 2025.

One more Earth flyby is planned for January 2029. Juice is targeted to arrive at Jupiter in July 2031 and to enter orbit around the moon Ganymede by 2034, ESA said.

Why it matters

Juice's route to Jupiter depends on a series of precise planetary flybys. A successful pass on September 28 keeps the mission on its planned path and preserves propellant for its main goal, studying Jupiter and its icy moons. The flyby also gave the team a chance to test and calibrate the instruments years before they reach the Jupiter system.

Sources

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