JUICE launch — to the icy moons

ESA's icy-moons explorer — in 2034 it becomes the first craft to orbit another planet's moon.

The moment of JUICE launch — to the icy moons: https://nowsky.org/e/juice-launch — opens at the right place and time, replayable, no login.

Available views: Orbit ✓ · Sky — (not visible in the sky)

The story

On 14 April 2023 ESA's JUICE left French Guiana on the penultimate flight of the Ariane 5, bound for Jupiter. The name stands for JUpiter ICy moons Explorer. It weighs six tonnes and carries 85 m² of solar panels — the area needed to wring 850 W from the faint sunlight at Jupiter's distance.

The route is an eight-year detour rather than a direct flight: an Earth–Moon double flyby in August 2024 (the first ever, passing the Moon and then Earth a day later), Venus in August 2025, Earth again in September 2026 and January 2029, and arrival at Jupiter planned for July 2031.

Once there it makes 35 close passes of Ganymede, Europa and Callisto, and in December 2034 enters orbit around Ganymede — the first spacecraft ever to orbit a moon of another planet. Among its ten instruments, the RIME radar penetrates up to 9 km of ice to map the roof of the subsurface ocean directly.

The launch fairing bore Galileo's 1610 sketches of Jupiter's moons, a tribute to their first observer. The capital "ICy" in the name marks where the mission's identity lies. The orbit view replays the chain of gravity assists.

Why it matters

JUICE is the first mission to compare the subsurface oceans of Europa, Ganymede and Callisto. Ganymede is the only moon in the solar system with its own magnetic field, and how that field couples to the buried ocean is the central question. NASA's Europa Clipper (arriving 2030) will view the same system from a different angle at the same time.

Entering orbit around another planet's moon is a new milestone in navigation. Being captured by a single moon inside Jupiter's gravity field demands both propellant and precision, and the experience will inform designs for Enceladus and Titan orbiters.

The eight-year detour was forced by the limits of the Ariane 5, but it allowed instrument calibration and observing rehearsals at Venus and Earth. The Earth–Moon double flyby of 2024 was a chance to test the instruments on the lunar surface and Earth's atmosphere for real.

How to watch

JUICE is now cruising between flybys in the inner solar system and cannot be seen from Earth. Select it in the orbit view for its current position and track, with the coming Earth flybys (September 2026, January 2029) marked as waypoints.

The orbit replay runs the chain of gravity assists from the April 2023 launch to the planned Jupiter arrival in July 2031; follow the probe at high speed and the orbit can be seen stretching outward at each Earth and Venus pass.

Jupiter, at magnitude −2, is among the brightest planets in the night sky, and binoculars show the four Galilean moons. Select Jupiter in the sky view for its position from your location, and zoom in on it in the orbit view for the orbits of Ganymede, Europa and Callisto.

See this for yourself — replay the moment in the orbit view

Background

JUICE was selected in 2012 as the first large-class science mission of ESA's Cosmic Vision programme. Originally a joint mission with NASA (EJSM), it was redesigned as a European mission when NASA withdrew in 2011, and NASA pursued Europa Clipper separately.

Just after launch the 16 m boom of the RIME radar antenna failed to deploy, and the control team wrestled with it for nearly a month. On 12 May the antenna finally unfolded after the spacecraft was shaken and turned toward the Sun to free a stuck pin.

After arrival in 2031 the first two years are spent in Jupiter orbit flying past the moons; after entering Ganymede orbit in December 2034 it observes for nine months from 500 km. The mission is scheduled to end in September 2035 with impact on Ganymede.

FAQ

Why does it take eight years?

The Ariane 5 could not send it directly; speed has to be built up with flybys of Earth, the Moon, Venus and Earth again.

When does it reach Jupiter?

Arrival is planned for July 2031, with Ganymede orbit insertion targeted for December 2034.

How does it differ from Europa Clipper?

JUICE compares three icy moons and orbits Ganymede; Clipper concentrates on Europa with repeated flybys.

How will it confirm the oceans?

The RIME radar penetrates up to 9 km of ice to map the ocean's roof, and the magnetometer measures the ocean's electrical signature.

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Times and figures are approximate — verify with official sources when planning travel. Simulation uses J2000 mean elements.