Juice is Fully Deployed. It’s Now in its Final Form, Ready to Meet Jupiter’s Moons in 2031

Launched on April 14, 2023, the European Space Agency’s (ESA) Jupiter Icy Moons Explorer (Juice; formerly known as JUICE) spacecraft has finally completed the unfurling of its solar panel arrays and plethora of booms, probes, and antennae while en route to the solar system’s largest planet.

However, Juice’s first six weeks in space haven’t been so smooth, as its Radar for Ice Moons Exploration (RIME) antenna became stuck and unable to deploy, but the engineers successfully deployed RIME after working the problem for over a month. The RIME unit is deemed as “mission critical” since its purpose is to map underneath the icy crusts of Jupiter’s three icy worlds: Europa, Ganymede, and Callisto.

“It’s been an exhausting but very exciting six weeks,” said Angela Dietz, who is the deputy spacecraft operations manager for the Juice mission. “We have faced and overcome various challenges to get Juice into the right shape for getting the best science out of its trip to Jupiter.”

The unfurling of the booms and antennae are crucial as they house either some or all of Juice’s 10 instruments, which comprise various scientific packages: the remote sensing package, the in situ package, and the geophysical package. Along with these incredible instruments, Juice will also be conducting an experiment known as the Planetary Radio Interferometer & Doppler Experiment (PRIDE), whose goal will be to use very-long baseline and ground-based interferometry to accurately measure Juice’s velocity and location in space.

This incredible cache of instruments will be responsible for exploring Jupiter while conducting 35 flybys of Europa, Ganymede, and Callisto, which are each hypothesized to contain bodies of liquid water beneath their icy crusts. Aside from the moons, Juice will also conduct further examinations of the entire Jupiter system, as scientists hypothesize this could help paint a clearer picture of gas giant exoplanets—and possible exomoons that have yet to be detected—that continue to be discovered throughout the galaxy.

Of the 10 Juice instruments, three stand out as some of the most important to the mission. These include the previously discussed RIME antenna, which will be responsible for mapping the interior environments of these icy worlds; the JANUS optical camera instrument, which will be able to capture images in 13 different colors, ranging from violet light to near infrared, and will be imaging Jupiter’s innermost Galilean moon, Io, as well; and the Radio & Plasma Wave Investigation (RPWI) instrument, which will be responsible for producing the first-ever 3D map of Jupiter’s electric fields and the interactions between Jupiter’s massive magnetosphere and the icy worlds of Europa, Ganymede, and Callisto.

“Our 3D design strategy makes it possible to measure true physical observables, such as energy and momentum, without resorting to theories or simulations to interpret the data,” said Jan Bergman, who is a Senior Scientists at the Swedish Institute of Space Physics and technical manager for RPWI.

As part of ongoing tests for all the instruments during Juice’s cruise to Jupiter, the team activated JANUS last week at approximately 8 million kilometers (5 million miles) from Earth and captured numerous images of eta Cyg—which lies in the Cygnus constellation—between 2 and 200 milliseconds (0.002 and 0.2 seconds).

During its trek to Jupiter, Juice will require some help to arrive by 2031. This begins with the first ever Lunar-Earth gravity assist maneuver in August 2024, meaning Juice will slingshot around the Moon followed by a slingshot around the Earth just 1.5 days later. By performing this maneuver, Juice will preserve a substantial amount of fuel during its mission. This will be followed by a Venus gravity assist in August 2025, then two more Earth-only gravity assists in September 2026 and January 2029, respectively, before Juice catapults its way to Jupiter for a scheduled July 2031 arrival. Juice’s primary mission is scheduled to only last four years, but with the 35 flybys of Europa, Ganymede, and Callisto, Juice should be able to accomplish a lot of science and teach us more about Jupiter and its many moons during that time.

What new discoveries will Juice teach us about Jupiter and its icy moons during its mission, and how will these discoveries shape our understanding of icy worlds and their potential habitability? Only time will tell, and this is why we science!

As always, keep doing science & keep looking up!