ESA’s Juice Spacecraft Gets Gravity Boost From Earth

The European Space Agency’s Jupiter Icy Moons Explorer (Juice) spacecraft made a close pass by Earth on September 28, using the planet’s gravity to alter its trajectory towards Jupiter while conserving fuel.

Juice passed about 8,640 kilometres above the Indian Ocean at 13:45 CEST (11:45 UTC), changing its direction by 20 degrees and increasing its speed by 3.5 kilometres per second.

The gravity-assist manoeuvre required highly precise navigation. Mission controllers made only one small course correction in the four weeks before the flyby, out of six planned opportunities to fine-tune the spacecraft’s approach.

“The flyby required ultra-precise navigation in real time,” said Angela Dietz, Juice spacecraft operations manager.

She said careful planning allowed the team to use only a small amount of the propellant reserved for the manoeuvre, leaving more fuel for observations at Jupiter and its icy moons.

The flyby also provided an opportunity to test Juice’s 10 scientific instruments using Earth as a planetary target.

It was the third such opportunity during the mission. The first came during Juice’s lunar-Earth gravity assist in 2024, while the spacecraft also observed Comet 3I/ATLAS in 2025.

ESA teams spent months coordinating operations of the spacecraft’s scientific instruments to maximise observations and calibration during the Earth encounter.

Juice project scientist Claire Vallat said the spacecraft’s journey to Jupiter offered only a few opportunities to calibrate and validate its instruments under well-understood conditions.

The teams prioritised activities based on their importance for Juice’s future observations of Jupiter and its icy moons, while taking into account the spacecraft’s limited power and operational constraints.

Mission controllers began particularly close monitoring of Juice on August 17 and are scheduled to continue intensive tracking through October 10.