ESA launches JUICE to Jupiter’s icy moons atop Ariane 5

by Justin Davenport

European Space Agency (ESA) and Arianespace teams have conducted the launch of the historic Jupiter Icy Moons Explorer (JUICE) mission to the three largest icy moons of Jupiter — Ganymede, Callisto, and Europa. The launch, dubbed Flight VA260, is the first of two Ariane 5 missions of 2023 and the penultimate flight of the Ariane 5 rocket, lofting JUICE on a trajectory that will result in a summer 2031 arrival and orbit insertion at the Jovian system.

JUICE lifted off at 12:14 UTC (9:14 AM local) on Friday, April 14, during an instantaneous launch window from pad ELA-3 at the Centre Spatial Guyanais (CSG) in Kourou, French Guiana. The 116th Ariane 5 mission flew a trajectory due east out over the Atlantic Ocean, inclined just shy of three degrees to the Equator.

JUICE’s Launch and Trajectory

JUICE arrived in French Guiana on Feb. 9, 2023, and has since undergone an intricate set of launch preparation procedures to prepare the spacecraft for its launch and coast to the Jovian system. The spacecraft was mated to the top of the Ariane 5 upper stage on April 5 and rolled out to pad ELA-3 on April 11.

JUICE’s eight-year journey to the Jovian system began with the ignition of Ariane 5’s twin solid rocket boosters and liftoff from pad ELA-3, with the ignition of the Vulcain 2 main engine occurring seven seconds before liftoff. Two minutes and 16 seconds following launch, the solid rocket boosters were jettisoned.

At three minutes and nine seconds into the flight, the fairing halves separated. The upper stage separated from the core stage at T+8:44 mission elapsed time (MET). After a very short coast phase, the upper stage’s HM-7B engine ignited at T+8:49.

The burn pushed the JUICE spacecraft, massing 5963 kilograms at launch, to a speed of 2.5 kilometers per second, giving the spacecraft enough energy to escape the Earth-Moon system. The upper stage shut down at T+25:25, with spacecraft separation occurring shortly after at T+27:45.

First contact with the spacecraft is scheduled to occur around T+32 minutes, and JUICE’s enormous 85 square-meter solar arrays will be deployed 67 minutes later at T+99 minutes. Given the distance between Jupiter and the Sun, these panels, which are the largest solar panels ever flown on an interplanetary spacecraft, need to be extremely large to capture adequate amounts of energy needed to operate the spacecraft.

From T+16 hours to T+17 days, JUICE will deploy its antennae, magnetometer, and probes. The spacecraft will not fly directly to Jupiter, as Ariane 5 is not powerful enough to place the spacecraft on a direct trajectory to the Jovian system. Instead, JUICE will use a trajectory similar in principle to trajectories used by many other spacecraft that travel to the outer solar system. With the help of four planetary flybys, or gravity assists, JUICE will gradually increase its velocity and orbital height until it reaches Jupiter’s orbital plane. As such, JUICE will first loop back to Earth, due to the Ariane 5 upper stage lacking restart capabilities.

The JUICE spacecraft. (Credit: ESA/ATG medialab)

Interplanetary probes launched by the Ariane 5, like BepiColombo and Rosetta, typically need to perform a flyby of Earth around a year after launch to change the inclination of their orbit around the Sun. JUICE’s first flyby of Earth will change JUICE’s trajectory from the near-equatorial plane to one suitable for continuing the mission to its next target; in this case, Venus. This first flyby of Earth won’t be any regular flyby of Earth, however, as JUICE will be performing a first-of-its-kind flyby of the Earth-Moon system called a Lunar-Earth Gravity Assist (LEGA). The maneuver will take place in August 2024 and will see JUICE fly past both the Moon and Earth, utilizing the gravity of both celestial bodies in a single flyby maneuver — saving a significant amount of propellant on the spacecraft for future use at Jupiter.

However, if JUICE’s launch is delayed past April 18, the LEGA flyby will not be able to be performed and will be replaced by a regular flyby of Earth.

Following the LEGA flyby, JUICE will perform a flyby of Venus in August 2025. Two more flybys of Earth are planned for September 2026 and January 2029 before JUICE’s orbital height reaches Jupiter’s, allowing the spacecraft to enter the Jovian system’s sphere of influence.

Mission milestones for JUICE. (Credit: ESA)

Furthermore, JUICE teams are currently evaluating the possibility of the spacecraft performing a flyby of an asteroid named 223 Rosa. 223 Rosa is a little smaller than asteroid 21 Lutetia, which ESA’s Rosetta mission flew past before reaching Comet 67P/Churyumov-Gerasimenko. This flyby would take place during the final coast of the mission between the spacecraft’s final Earth flyby and arrival at Jupiter. If teams opt to fly past the asteroid, the flyby will serve as a dress rehearsal for JUICE’s upcoming icy moon flybys.

JUICE’s Mission at Jupiter

After the long journey to Jupiter, if all goes as planned, JUICE will arrive at the Jovian system in July 2031 equipped with 10 instruments, utilizing hardware provided by ESA, NASA, the Japan Aerospace Exploration Agency (JAXA), and the Italian Space Agency (ASI). After arriving at the Jovian system, the spacecraft is expected to perform at least 35 flybys of the icy moons Ganymede, Callisto, and Europa.

After these flybys, JUICE will enter into orbit around Ganymede in December 2034. JUICE will remain in orbit around Ganymede for most of 2035 before using its remaining propellant to deorbit itself and crash into Ganymede, concluding its mission. However, the end of JUICE’s mission could be changed if there is found to be a possibility that the impact could contaminate the liquid ocean believed to be under Ganymede’s icy crust.

JUICE’s primary purpose is to study Jupiter’s three icy moons, each of which is believed to contain a liquid ocean under their icy crusts. Ganymede, in particular, will be the main focus of this mission, though there will be flybys of heavily-cratered Callisto and ice-covered Europa as well.

JUICE will also study Jupiter’s complex environment and how it relates to its moons. It is hoped that the mission will help answer key questions about Jupiter and its moons. These questions include the potential for life and why Ganymede, the largest moon in the Solar System, is the only moon in the Solar System to host a magnetic field.

The development of JUICE lasted for around a decade, with the spacecraft finally being fully integrated in April 2022. After completing critical tests of spacecraft components (i.e. solar array deployment and thermal vacuum testing), JUICE was shipped to French Guiana aboard a Ukrainian Antonov AN-124 cargo transport aircraft two months before its April 2023 launch.

Ariane 5 ECA for VA260 rolling out to the BAF for mating with JUICE. (Credit: ESA)

JUICE’s launch processing began soon after its arrival in French Guiana, with spacecraft fueling being completed in March. The Ariane 5 ECA’s core and boosters were assembled in the Launcher Integration Building (BIL) before its rollout to the Final Assembly Building (BAF), where it was mated with JUICE, which was then encapsulated in its fairing halves.

Around 12 hours before launch, the last Ariane 5 to be built, with JUICE on board, rolled out from the BAF to the ELA-3 launch pad. The JUICE mission then will have until April 30 to get off the ground or face an extended delay while the teams wait for the next Jupiter transfer window.

(Lead image: JUICE’s rolls out to pad ELA-3 atop Ariane 5 on April 11. Credit: ESA)

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