LOS ANGELES, California, September 28, 2026 — Juice — the European Space Agency’s Jupiter Icy Moons Explorer mission — makes a flyby of Earth on Monday as it heads to the icy moons around the giant planet. The spacecraft sweeps within 8,640 kilometers of the surface over the Indian Ocean. That gravity assist bends its trajectory and gives it some velocity boost without burning any of the rocket’s fuel.
Why Juice Needs Earth
Juice flew to space onboard an Ariane 5 from Europe’s Spaceport near Kourou in French Guiana in April 2023. It would take far more fuel than can fit on a spacecraft, both to depart Earth and decelerate upon arrival. A route is constructed by mission planners, which steals energy from planets along its path.
In August 2024, the spacecraft flew past the Moon and Earth, then bent its orbit toward Jupiter even more at a flyby of Venus in August 2025. This pass on Monday is its third gravity assist, with another Earth flyby planned in January 2029. Juice is planned to arrive at Jupiter in July 2031.
The flybys also serve to validate the spacecraft systems in practice. At the European Space Operations Centre in Darmstadt, Germany, flight controllers here began preparations for the encounter in August. They allotted a bunch of intervals for minor trajectory adjustments to maintain accuracy on approach.
Working in Earth’s Shadow
Juice was expected to reside in Earth’s shadow, where it has no direct sunlight, for roughly nine hours before closest approach. During that period, the spacecraft solely operates on battery power. So the flight teams prioritized which of the most important science observations were to be taken care of before completely draining the batteries.
Starting with all 10 of Juice’s science instruments turned on to look at Earth and the Moon during Sept., the data allows instrument teams to calibrate their instruments on known targets and validate analysis tools. Those flags set them up for the much more remote observations later on.
Moons Worth the Trip
Juice will go to Ganymede, Callisto and Europa — three of Jupiter’s big moons which researchers suspect harbor oceans under icy crusts. At present, good candidates in the solar system to search for life include Europa. The main target of the mission: Ganymede and Callisto.
It carries a radar instrument capable of peering up to 9 km deep into the icy crusts of these moons. Others will measure the surfaces and magnetic fields, as well as characteristics of Jupiter itself. Running together they ought to show how deep the ice goes and where liquid water could shield.
Juice is scheduled to go into orbit around Ganymede in December 2034 for months of detailed observations. The cruise phase of the mission will last for eight years, then there will be approximately three and a half years of science. Which means that most results are not coming until the 2030s.
What Comes Next
Juice is a mission from the European Space Agency that Incapsula built for Airbus Defence and Space. At launch, the spacecraft was approximately 6,070 kilograms (13,400 lb), including nearly 3,000 kilograms of chemical propellant. The spacecraft has a span of more than 27 meters from its solar arrays and antennas.
During the pass, some lucky skywatchers in portions of Australia may also glimpse the spacecraft in binoculars or a telescope. The majority of the value will be derived from data collected during the flyby by the in situ instruments, mostly within days of the planetary encounter. That data is then transmitted back to Earth and published by the European Space Agency with frequent mission updates.
Following this flyby, Juice will head on toward Jupiter over the course of almost five additional years before its lengthy science mission begins. The wait is agonizing, but success could change the ground rules for finding habitable worlds beyond Earth. With every flyby, the spacecraft comes closer to achieving that, and the January 2029 pass will determine its final trajectory.
