Jupiter Icy Moons Explorer

The Jupiter Icy Moons Explorer (Juice, formerly JUICE) is an interplanetary spacecraft on its way to orbit and study three icy moons of Jupiter: Ganymede, Callisto, and Europa. These planetary-mass moons are planned to be studied because they are thought to have significant bodies of liquid water beneath their frozen surfaces, which would make them potentially habitable for extraterrestrial life.
Juice is the first interplanetary spacecraft to the outer Solar System planets not launched by the United States and the first set to orbit a moon other than Earth's Moon. Launched by the European Space Agency (ESA), from Guiana Space Centre in French Guiana on 14 April 2023, with Airbus Defence and Space as the main contractor, it is expected to reach Jupiter in July 2031 after four gravity assists and eight years of travel. In December 2034, the spacecraft will enter orbit around Ganymede for its close-up science mission. Its period of operations will overlap with NASA's Europa Clipper mission, which was launched in October 2024.
The mission started as a reformulation of the Jupiter Ganymede Orbiter proposal, which was to be ESA's component of the cancelled Europa Jupiter System Mission – Laplace (EJSM-Laplace). It became a candidate for the first L-class mission (L1) of the ESA Cosmic Vision Programme, and its selection was announced on 2 May 2012.
In April 2012, Juice was recommended over the proposed Advanced Telescope for High Energy Astrophysics (ATHENA) X-ray telescope and a gravitational wave observatory (New Gravitational wave Observatory (NGO)).
In July 2015, Airbus Defence and Space was selected as the prime contractor to design and build the probe, to be assembled in Toulouse, France.
By 2023, the mission was estimated to cost ESA 1.5 billion euros ($1.6 billion).
The main spacecraft design drivers are related to the large distance to the Sun, the use of solar power, and Jupiter's harsh radiation environment. The orbit insertions at Jupiter and Ganymede and the large number of flyby manoeuvres (more than 25 gravity assists, and two Europa flybys) require the spacecraft to carry about 3,000 kg (6,600 lb) of chemical propellant. The total delta-V capability of the spacecraft is about 2,700 m/s (6,000 mph).
Juice has a fixed 2.5 meter diameter high-gain antenna and a steerable medium-gain antenna; both X- and K-band will be used. Downlink rates of 2 Gb/day are possible with ground-based Deep Space Antennas. On-board data storage capability is 1.25 Tb.
The Juice main engine is a hypergolic bi-propellant (mono-methyl hydrazine and mixed oxides of nitrogen) 425 N thruster. A 100 kg multilayer insulation provides thermal control. The spacecraft is 3-axis stabilized using momentum wheels. Radiation shielding is used to protect onboard electronics from the Jovian environment (the required radiation tolerance is 50 kilorad at equipment level).
The Juice science payload has a mass of 280 kilograms (620 lb) and includes the JANUS camera system, the MAJIS visible and infrared imaging spectrometer, the UVS ultraviolet imaging spectrograph, RIME radar sounder, GALA laser altimeter, SWI submillimetre wave instrument, J-MAG magnetometer, PEP particle and plasma package, RPWI radio and plasma wave investigation, 3GM radio science package, the PRIDE radio science instrument, and the RADEM radiation monitor. A 10.6 meters (35 ft) deployable boom will hold J-MAG and RPWI, a 16 meters (52 ft) long deployable antenna will be used for RIME. Four 3 meters (9.8 ft) booms carry parts of the RPWI instrument. The other instruments are mounted on the spacecraft body, or for 3GM, within the spacecraft bus.
Juice was launched into space on 14 April 2023 from the Guiana Space Centre on an Ariane 5 rocket. This was the final launch of an ESA science mission using the Ariane 5 vehicle, and was the second to last launch of the rocket overall.
The launch was originally scheduled for 13 April 2023, but due to poor weather the launch was postponed. The next day a second launch attempt succeeded, with liftoff occurring at 12:14:36 UTC. After the spacecraft separated from the rocket, it established a successful radio signal connection with the ground at 13:04 UTC. Juice's solar arrays were deployed about half an hour later, prompting ESA to deem the launch a success.
Following the launch, there will be multiple planned gravity assists to put Juice on a trajectory to Jupiter:
Juice will pass through the asteroid belt twice. A flyby of the asteroid 223 Rosa was proposed to occur in October 2029, but was abandoned to save fuel for the primary Jovian mission.
Gravity assists include:
The main characteristics of the Jupiter reference tour are summarised below (source: Table 5-2 of ESA/SRE(2014)1). This scenario assumed an early June 2022 launch, however, the delta-V requirements are representative due to the rather short, repetitive orbital configurations of Europa, Ganymede and Callisto.
The Juice orbiter will perform detailed investigations on Ganymede and evaluate its potential to support life. Investigations of Europa and Callisto will complete a comparative picture of these Galilean moons. The three moons are thought to harbour internal liquid water oceans, and so are central to understanding the habitability of icy worlds.
The main science objectives for Ganymede, and to a lesser extent for Callisto, are:
For Europa, the focus is on the chemistry essential to life, including organic molecules, and on understanding the formation of surface features and the composition of the non-water-ice material. Furthermore, Juice will provide the first subsurface sounding of the moon, including the first determination of the minimal thickness of the icy crust over the most recently volcanically-active regions.
More distant spatially resolved observations will also be carried out for several minor irregular satellites and the volcanically active moon Io.
On 21 February 2013, after a competition, 11 science instruments were selected by ESA, which were developed by science and engineering teams from all over Europe, with participation from the US. Japan also contributed several components for SWI, RPWI, GALA, PEP, JANUS and J-MAG instruments, and will facilitate testing.