JUICE launch — to the icy moons
ESA's JUICE left for Jupiter's icy moons on 14 April 2023. It is due at Jupiter in 2031 and is planned to go into orbit around the moon Ganymede in 2034.
Available views: Orbit ✓ · Sky — (not visible in the sky)
The story
On 14 April 2023 the European Space Agency's JUICE spacecraft left French Guiana in South America on an Ariane 5 rocket, bound for Jupiter. The name is short for JUpiter ICy moons Explorer. Several of Jupiter's large moons are covered with thick shells of ice, and the mission's job is to find out what lies beneath them.
JUICE weighs about six tonnes and carries roughly 85 square metres of solar panels, about a third of a tennis court. Jupiter is about five times farther from the Sun than Earth is, so sunlight there is only about one twenty-fifth as strong. Such a large area is needed just to collect around 850 watts, enough for a handful of household light bulbs.
JUICE does not fly straight to Jupiter. It takes an eight-year detour. In August 2024 it passed the Moon and, a day later, Earth, the first time a spacecraft had used the two in a row like that. It flew past Venus in August 2025 and past Earth again on 28 September 2026. Each close pass uses a planet's gravity to change the spacecraft's speed and direction.
After a last Earth flyby in January 2029, JUICE is due to reach Jupiter in July 2031. It will then pass Ganymede, Callisto and Europa many times, and in December 2034 it is planned to enter orbit around Ganymede. If that works it will be the first spacecraft to orbit a moon of another planet. The orbit view replays the journey, showing the orbit growing larger after each pass of Earth and Venus.
Mission goals
Scientists think there are oceans of liquid water under the ice of Ganymede, Europa and Callisto. JUICE is built to compare all three with the same instruments. Ganymede is special: it is the only moon in the solar system known to make its own magnetic field. How that field interacts with the hidden ocean is one of the mission's central questions.
JUICE carries ten instruments. One of them, the RIME radar, sends radio waves into the ice and can see as deep as about 9 km. That shows how thick the ice shell is and whether pockets of water sit inside it. A magnetometer measures the faint electrical signal that a salty ocean produces, which is one of the best ways to confirm the ocean is really there.
NASA's Europa Clipper arrives at Jupiter at about the same time, in 2030. Clipper concentrates on Europa, while JUICE compares three moons and then settles into orbit around Ganymede. Together the two missions will look at the Jupiter system from different angles.
Mission chronology and background
JUICE was chosen in 2012 as the first large science mission of ESA's Cosmic Vision programme. It began as part of a joint plan with NASA to send two spacecraft to the Jupiter system, but NASA withdrew in 2011 for budget reasons, and the mission was redesigned for Europe to fly alone. NASA later went ahead with Europa Clipper on its own.
Soon after launch a problem appeared. The 16-metre antenna of the RIME radar stayed folded and would not open. For nearly a month the control team tried one thing after another. They concluded that a small pin was stuck and tried shaking the spacecraft to free it. On 12 May 2023 the antenna finally unfolded.
After arrival the first years are spent orbiting Jupiter and flying past its moons. In December 2034 JUICE is planned to enter orbit around Ganymede and observe from about 500 km up. Near the end of 2035, with its fuel used up, it is expected to crash onto Ganymede's surface.
Other milestones of this mission
Where to see it — sky and simulator
JUICE has just passed close to Earth, but it is still far too small and faint to see by eye or through a telescope. Select it in the orbit view to see where it is now, the path it has already flown and the point of its last Earth flyby in January 2029. Speed up the clock and the route continues to arrival at Jupiter in 2031.
Its destination, Jupiter, is easy to find without any equipment. It is one of the brightest planets in the night sky, and ordinary binoculars show four tiny points of light lined up beside it. One of them is Ganymede. Select Jupiter in the sky view to see where it is now, and zoom in on it in the orbit view to see the orbits of the four large moons.
See this for yourself — replay the moment in the orbit view
FAQ
Why does it take eight years?
The rocket alone could not send it straight there. It gathers speed by flying past the Moon, Earth and Venus in turn before heading out to Jupiter.
When does it reach Jupiter?
Arrival is planned for July 2031, and entry into orbit around Ganymede for December 2034.
How is it different from Europa Clipper?
Clipper focuses on Europa with many close passes. JUICE compares Ganymede, Europa and Callisto and finally goes into orbit around Ganymede.
How will it check for hidden oceans?
Its radar looks up to 9 km into the ice, and its magnetometer measures the faint electrical signal made by salty water. Together they show whether an ocean is there.
Related
Times and figures are approximate — verify with official sources when planning travel. Simulation uses J2000 mean elements.