It’s the great planetary mission of the European Space Agency: Juice will leave Earth on April 13 to study the icy moons of Jupiter. The journey will last 8 years. Once arrived, the probe will make 35 flybys before going into orbit around Ganymede. Objective: to check whether these moons are potentially habitable.
If Juice has to be summed up in a few figures, let’s remember these: 2,000 employees, 18 establishments, 23 participating countries, 83 partner companies through 116 contracts under the prime contractorship of Airbus Defense & Space, all for a budget total of 1.6 billion euros. Futura visited the clean room several times in Toulouse, where the Juice probe underwent tests for more than a year before leaving for Kourou. It is a whole community that orbits around this mission responding to new scientific objectives.
Never have the moons of Jupiter been scrutinized so closely. Jupiter has already been visited by NASA probes before, with flybys of the Pioneer, Voyager, Ulysses, New Horizons, Cassini probes, but also the Galileo and Juno orbiters (still active). Juice is of a new generation, one that seeks to answer the question of the potential existence of elementary extraterrestrial life in the Jovian system with, as targets, the moons Europa, Ganymede and Callisto.
Oceans under ice and magnetism
The scientific objectives of Juice are multiple but above all of a new nature. They echo the new questions that we draw from the legacy of the exploration of the Jovian system until today, in a context where we now know thousands of exoplanets of the same nature as Jupiter.
Livability is arguably the most exciting concept. The community is now sure that there is an ocean under the icy surfaces of Europa, Ganymede and Callisto. The presence of liquid water suggests the existence of extraterrestrial life. Without being able to detect it, Juice will characterize these three moons to find out if this life is possible or not.
The study of the exo-Jupiters puts on the table the question of their formation, as well as that of their ecosystem. It is therefore a question of characterizing the magnetism of Jupiter and knowing how it interacts with the atmosphere of the planet as well as with the moons, in particular Ganymede, the only one to have its own magnetic field. This is to learn more regarding the rings of Jupiter, the other moons of the Jovian system, including Io, and also regarding the atmosphere of the giant planet.
A (very) long trip
Takeoff is scheduled for April 13, at 2:15 p.m., from the Guiana Space Center aboard the penultimate flight of Ariane 5. A heavy launcher is needed to be able to send the 5,100-kilogram probe to Jupiter. Of this mass, 2,900 kilos are fuel. To allow the most operations on site, it will be used sparingly. Thus, a direct path to Jupiter is excluded and several gravitational assistances are planned:
- August 2024: flyby of the Moon and the Earth;
- August 2025: flyby of Venus;
- September 2026: Earth flyby;
- January 2029: Earth flyby.
The arrival in the Jovian system is scheduled for July 2031, following 8 years of travel! The scientific instruments will be switched on, tested and calibrated during the various overflights. Once arrived, the Juice probe will have enough fuel to carry out 12 flybys of Ganymede, 21 flybys of Callisto, and 2 flybys of Europe. The latter is avoided because its radiative environment is very harsh, then the moon will be targeted by NASA’s Europa Clipper mission, supposed to land on it around 2030.
Voyage of the Juice probe and visit of the Jovian system. © ESA, YOUTUBE
Strong scientific instrumentation
The probe’s satellite platform has been sufficiently optimized to accommodate 285 kilos of scientific instruments. Juice counts ten, as well as a radiation monitor (Raem). The instruments include an optical camera (Janus), a visible and near-infrared spectrometer-imager developed by the Space Astrophysics Institute (Majis), instruments for making sub-millimeter measurements (SWI), radar ( Rime) and radio and plasma waves (RPWI), an ultraviolet spectrograph (UVS, provided by NASA), a laser altimeter (Gala), a magnetometer (J-MAG), a radio science experiment (3GM), and a particle sensor (PEP).
The instruments are under French, German, British, Italian, Dutch, Swedish, and American project management for UVS. American laboratories also participated in other instruments, as well as the Japanese space agency. These instruments are designed to operate in the harsh environment of Jupiter. Juice has radiation protection, layers of MLI (multi-layer insulation blanket) to withstand extreme temperatures (ranging from -230°C around Jupiter to +250°C when flying over Venus). Finally, to supply all the systems with energy, ESA has chosen to equip the probe with solar panels rather than using an RTG. Given the distance from the Sun, the area of the panels reaches 85 m².