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Ariane 5 to launch Europe’s first mission to Jupiter

The JUICE mission aims to study the Jupiter system and its icy moons, Ganymede, Callisto, and Europa

On April 14, the European Space Agency's Jupiter Icy Moons Explorer (JUICE) is scheduled to launch on an Ariane 5 no.L5120 rocket from Kourou, French Guiana, marking Europe's first mission to Jupiter. The six-ton spacecraft will embark on a long journey, performing several gravity-assist flybys of the Earth and Venus between August 2024 and January 2029 before reaching Jupiter in mid-2031. JUICE will conduct 35 flybys of Jupiter's largest moons, Europa, Ganymede, and Callisto before entering orbit around Ganymede, where it will focus on characterizing the liquid water oceans inside the icy moon.

Lift-off is scheduled at 1214 UTC (09:14 Kourou / 08:14 EDT / 14:14 Paris).

The launch attempt scheduled for April 13 has been delayed due to bad weather.

The Flight VA260 is also the penultimate flight for the Ariane 5. and it will be the last ESA mission to launch on an Ariane 5 from European Spaceport in Kourou, before Ariane 6 takes over.

The JUICE mission is a collaboration between ESA and multiple scientific institutions across Europe, as well as NASA. It is the first large-class mission in ESA's Cosmic Vision program and is expected to provide important insights into the formation and evolution of the Jupiter system, as well as the potential for life beyond Earth.

JUICE Mission was made ready for Jupiter

In 2014, The European Space Agency (ESA) has given approval to prime contractor Airbus and its partners to build a prototype spacecraft for the challenging Jupiter Icy Moon Explorer (Juice) mission. The project, costing €1.5bn ($1.62bn in 2014), will be Europe’s first attempt to explore the solar system’s largest planet and its moons at close quarters. The mission is expected to launch in 2022 and will involve performing several flybys of Jupiter. The spacecraft’s 10 scientific instruments, including cameras and sensors to monitor the magnetic field, will be paid for by the national space agencies of ESA’s member states. More than 60 companies will be involved in building the components for the spacecraft. Juice’s 100-square-meter solar array will be the largest to ever be flown by Europe and will be made by Germany’s Azur Space.

Juice will spend approximately eight years cruising to Jupiter, during which it will complete fly-bys of Venus, Earth and the Earth-Moon system. It will reach Jupiter in July 2031; Juice will begin its science mission six months before entering orbit around Jupiter, observing as it approaches. It will then spend four years studying Jupiter and its largest moons, Ganymede, Callisto, and Europa. During the tour, Juice will make two flybys of Europa, searching for pockets of liquid water, studying its surface composition and geology, and investigating its atmosphere.

A sequence of flybys of Callisto will allow Juice to study the polar regions and environment of Jupiter at higher latitudes, and a sequence of flybys of Ganymede and Callisto will enable it to enter orbit around Ganymede. Ganymede is unique in the Solar System in that it is the only moon with a magnetosphere, and Juice will investigate this phenomenon, as well as the moon’s internal magnetic field and its atmosphere, surface, subsurface, interior, and internal ocean. Juice’s orbit around Ganymede will eventually decay, and it will make a grazing impact onto the surface in late 2035.

Environmental Challenges for JUICE Mission

The Juice spacecraft will face the challenge of receiving adequate solar power while out at Jupiter, receiving only 3% of the solar illumination available at Earth orbit. The solar cell technology on Juice has improved, but the Solar Generators section still needed to ensure the state-of-the-art cells worked in Jupiter’s cold darkness. Juice will carry 10 instruments in total, which meant the spacecraft had to remain clean in magnetic and plasma terms to ensure the instruments collect accurate data on Jupiter space.

The Juice spacecraft is equipped with unique solar panels, antennas, probes, and booms to overcome challenges no other European mission has faced. To keep the equipment safe during launch, everything will be tucked away and deployed once Juice separates from its Ariane 5 host rocket

The solar arrays will be deployed after T+50 minutes, and the medium-gain antenna will be deployed after 16 hours. After five days, the Radar for Icy Moons Exploration (RIME) antenna will be deployed, and after 10 days, the magnetometer boom will be deployed. The Radio Wave Instrument (RWI) antennas will be deployed after 12 days, and the four Langmuir Probes will be deployed between 13 and 17 days after launch.

Juice has a distinctively shaped solar array – two ‘wings’ of panels in a cross-like formation. Overall, these wings are made up of ten 2.5 x 3.5 m panels (five on each side) with a total area of 85 m2 (and a total of 23 560 solar cells) – the largest ever built for an interplanetary spacecraft, measuring 27 m from tip to tip. Their shape allows them to be large in size but also to fold up neatly inside the launcher so they can leave Earth’s surface and successfully deploy in space.

The large area of Juice’s solar ‘wings’ produces sufficient power for the spacecraft’s onboard systems and instruments – approximately 850 W – despite operating so far from the Sun.

The Juice spacecraft will need to be self-reliant due to the 45-minute delay in sending signals to Earth. This means that if something goes wrong, it cannot be recovered in real time. There are two pivotal orbital insertion manoeuvres that must happen as planned, which could lead to mission loss if interrupted. To address this, the ESA's Flight Software Systems section developed a 'Failure, Detection, Isolation and Recovery' strategy that allows for local or subsystem reconfiguration before resorting to safe mode. The spacecraft should be capable of resuming critical manoeuvres autonomously even if it enters safe mode.

Safe Mode

Juice is designed to switch automatically between nominal and redundant units to avoid safe mode during critical mission phases. Redundant units are kept 'warm' and ready to activate quickly if required. In the event of failure of key systems, such as gyroscopes, solar array drive mechanism, and reaction wheels, the spacecraft would switch to the spare units or use thrusters. The mission has multiple safe mode configurations, keeping different units active to avoid a total shut down. A full Juice safe mode would trigger a reboot of the spacecraft’s main computer and mass memory, using a minimum of context data for its configuration.


The JUICE spacecraft will carry the most powerful remote sensing, geophysical, and in situ payload complement ever flown to the outer Solar System. The spacecraft is roughly cuboidal, with two large cross-shaped ‘wings’ of solar panels on either side, several extending booms and antennas, and a large dish-shaped antenna on one face (Juice’s High Gain Antenna).

Dimensions (stowed for launch): 4.09 x 2.86 x 4.35 m

Dimensions (deployed in orbit): 16.8 x 27.1 x 13.7 m

Dry mass (without fuel): 2420 kg. This includes the 'payload adapter' that connects the satellite to the launcher.

Amount of propellant (full tank): 3650 kg. This is a reasonably large volume compared to the spacecraft’s dry mass due to Juice’s numerous planned flybys, manoeuvres and change of orbit from Jupiter to Ganymede (and subsequent necessary orbital reductions at Ganymede).

Instrument payload mass: 280 kg

The payload consists of 10 state-of-the-art instruments and one experiment that uses the spacecraft telecommunication system with ground-based instruments. This payload is capable of addressing all of the mission's science goals, from in situ measurements of Jupiter's atmosphere and plasma environment, to remote observations of the surface and interior of the three icy Galilean moons in Jupiter's orbit.

A remote sensing package includes imaging (JANUS) and spectral-imaging capabilities from the ultraviolet to the sub-millimetre wavelengths (MAJIS, UVS, SWI). A geophysical package consists of a laser altimeter (GALA) and a radar sounder (RIME) for exploring the surface and subsurface of the moons, and a radio science experiment (3GM) to probe the atmospheres of Jupiter and its satellites and to perform measurements of the gravity fields. An in situ package comprises a powerful package to study the particle environment (PEP), a magnetometer (J-MAG) and a radio and plasma wave instrument (RPWI), including electric fields sensors and a Langmuir probe. An experiment (PRIDE) using ground-based very-long-baseline interferometry will provide precise determination of the spacecraft position and velocity.

JUICE will be joined by NASA’s Europa Clipper mission, scheduled to launch in October 2024 and arrive at Jupiter in 2030. That spacecraft will conduct dozens of flybys of Europa to study the potential for life on that icy moon.



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