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.[18] In 2024, Airbus Defence and Space received the Excellence Award from ESA for their work on Juice.[19] By 2023, the mission was estimated to cost ESA 1.5 billion euros ($1.6 billion).[20]
Spacecraft
Juice in Airbus Astrolabe facilities, 2023Operating in an extreme environment around JupiterJuice flyby of Callisto
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.[21] The total delta-V capability of the spacecraft is about 2,700 m/s (6,000 mph).[22]
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.[1]
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[1] (the required radiation tolerance is 50 kilorad at equipment level[22]).
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.[1]
Mission timeline
Launch
Ariane 5 launch of JuiceJuice's RIME antenna deploys
The launch was originally scheduled for 13 April 2023, but due to poor weather the launch was postponed.[25] 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.[23]
During post-launch commissioning of the spacecraft, the RIME antenna failed to properly deploy from its mounting bracket.[26] After several weeks of attempts to free the instrument, it was successfully deployed on 12 May of the same year.[27]
Earth-Moon system flyby
Juice images the particle cloud around Earth during the 2024 flyby
In August 2024, Juice performed its first gravity assist when it flew by the Moon and then Earth, becoming the first ever spacecraft to perform such maneuver using both bodies. The closest approach to the Moon happened at 21:15 UTC on 19 August. This increased the spacecraft's speed by 0.9 km/s relative to the Sun, sending it towards Earth. The closest approach to Earth happened at 21:56 UTC on 20 August. This reduced the spacecraft's speed by 4.8 km/s relative to the Sun, sending it towards Venus for the next gravity assist planned for August 2025. This double gravity assist saved the spacecraft up to 150 kg of fuel and deflected it by an angle of 100° compared to its path before the flyby.[28]
During this maneuver, Juice tested many of its scientific instruments. All 10 instruments were active during the Moon flyby, and eight during the Earth flyby. The JANUS camera took high-resolution images of the Moon and Earth.[28] The MAJIS and SWI instruments detected the expected chemical signatures of habitability on Earth and MAJIS also provided information-rich temperature maps of Earth.[29][30] Two sensors of the Particle Environment Package (PEP) took pictures and in situ measurements of the charged particle cloud surrounding Earth.[31] The RIME radar sounder captured a radargram image of the patch of the lunar surface that is also visible in the famous Earthrise photo, taken in 1968 during the Apollo 8 mission.[32]
Venus flyby
On 16 July 2025, during a time-sensitive period before the planned Venus flyby, Juice experienced a communication anomaly that temporarily severed the spacecraft's contact with Earth. After almost 20 hours of recovery efforts, ESOC and Airbus managed to resolve the issue and identified its root cause related to a scheduled restart of the spacecraft's internal timer. Plans for the flyby remained unchanged[33] and Juice successfully flew by Venus on 31 August 2025, with the closest approach of 5088 km above Venus's surface at 05:28 UTC, performing a gravity assist maneuver that increased its velocity by 5.1 km/s and sent it towards its second Earth flyby planned for September 2026. Due to thermal constraints (solar flux of 3000 W/m2 near Venus versus 50 W/m2 near Jupiter), no imaging or scientific observations were planned for the Venus flyby and the spacecraft used its high-gain antenna as a thermal shield, pointing it toward the Sun.[34][35]
3I/ATLAS observations
The interstellar comet 3I/ATLAS, discovered in July 2025 as only the third known interstellar object in the Solar System, is expected to make its closest approach to the Sun in October 2025. However, this part of its trajectory, when it is expected to show strong cometary activity, will not be visible from Earth-based telescopes as it occurs on the other side of the Sun. As of September 2025, ESA expects that of all its interplanetary spacecraft, Juice will have the best conditions for observing the object during its close approach to the Sun. Juice will attempt to observe 3I/ATLAS in November 2025, at a distance of 0.428 AU,[36] using its cameras, spectrometers, and a particle sensor. ESA is also considering coordinating ultraviolet spectrograph observations with NASA's Europa Clipper. Due to the challenging thermal conditions during Juice's travel through the inner Solar System, the data from these observations are not expected to reach Earth before February 2026.[37][38]
Trajectory
Juice's journey to Jupiter
Following the launch, multiple gravity assists are needed to put Juice on a trajectory to Jupiter:[8][23]
Flyby of the Earth–Moon system, completed in August 2024[39]
Juice passes 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.[40][41][42]
Gravity assists within the Jovian system include:[43]
Jupiter orbit insertion and apocentre reduction with multiple Ganymede gravity assists
Reduction of velocity with Ganymede–Callisto assists
Increase inclination with 10–12 Callisto gravity assists
Trajectories of Juice
Around the Sun
Around Jupiter
Around Ganymede
Sun· Earth· Juice· Venus·223 Rosa· Jupiter· Ganymede· Callisto · Europa
On its journey Juice will make a series of flybys of Earth, the Earth-Moon system and Venus to set it on course for its July 2031 rendezvous in the Jovian system
Jupiter mission phases
The main characteristics of the Jupiter reference tour are summarised below (source: Table 5-2 of ESA/SRE(2014)1[22]). 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.
When it arrives in the Jovian system in July 2031,[8]Juice will first perform a 400 km (250 mi) Ganymede gravity assist flyby to reduce spacecraft velocity by ~300 m/s (670 mph), followed by ~900 m/s (2,000 mph) Jupiter orbit insertion engine burn ~7.5 hours later. Finally, a Perijove Raising Manoeuvre (PRM) burn at apoapsis will raise the periapsis of Juice's initial 13x243 Jovian radii elongated orbit to match that of Ganymede (15 Rj).
186 days
952 m/s (2,130 mph).
2nd Ganymede flyby to initial encounter with Callisto: 2nd, 3rd and 4th Ganymede flyby to reduce the orbital period and inclination of Juice's orbit, followed by 1st flyby of Callisto.
193 days
27 m/s (60 mph).
Europa phase: Starting in July 2032,[8] there will be two <400 km (250 mi) flybys of Europa followed by another Callisto flyby. The brief Europa encounters (during which the probe is expected to sustain a third of its lifetime radiation exposure[44]) are planned such that the radiation exposure is as low as possible, first by encountering Europa at perijove (i.e. the spacecraft's perijove is equal to Europa’s orbital radius), and second by having only one low perijove passage per Europa flyby.
35 days
30 m/s (67 mph).
Inclined phase: ~6 further flybys of Callisto and Ganymede to temporarily increase the orbital inclination to 22 degrees. This will allow an investigation of Jupiter's polar regions and Jupiter's magnetosphere[8] at the maximum inclination over a four-month period.
208 days
13 m/s (29 mph).
Transfer to Ganymede: A series of Callisto and Ganymede gravity assists will be performed to gradually reduce Juice's speed by 1,600 m/s (3,600 mph). Finally, a series of distant ~45,000 km (28,000 mi) flybys of the far side of Ganymede (near the Jupiter-Ganymede-L2 Lagrange point) will further reduce the required orbital insertion delta-V by 500 m/s (1,100 mph).
353 days
60 m/s (130 mph).
Ganymede orbital phase: In December 2034,[8]Juice will enter an initial 12-hour polar orbit around Ganymede after performing a 185 m/s (410 mph) delta-V braking burn. Jupiter gravitational perturbations will gradually reduce the minimum orbital altitude to 500 km (310 mi) after ~100 days. The spacecraft will then perform two major engine firings to enter a nearly circular 500 km (310 mi) polar orbit, for a further six months of observations (e.g. Ganymede's composition and magnetosphere).[8] The orbital phase includes a final stage at 200 km altitude.[45] At the end of 2035, Jupiter perturbations will cause Juice to impact onto Ganymede within weeks as the spacecraft runs out of propellant.[8]
284 days
614 m/s (1,370 mph).
Full tour (Jupiter orbit insertion to end of mission)
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. The chemical investigations will be focused also on the question which chemicals originated underground and were brought to the surface by tectonics or cryovolcanism, and which arrived from above, originating at other places within the Jovian system.[47]
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. Juice will be able to determine if pockets of liquid water exist within the ice and possibly also probe the interface between the icy shell and the subsurface ocean.[47]
Other moons and Jupiter's rings
More distant spatially resolved observations will also be carried out for several minor irregular satellites and the volcanically active moon Io. Juice will monitor the volcanic activity of Io and study the composition of its surface materials. The mission will also observe Jupiter's dusty rings and study their interactions with the small irregular moons like Metis, Adrastea, Amalthea, and Thebe.[48]
Jupiter's atmosphere and magnetosphere
Juice will repeatedly map Jupiter's atmosphere and use its instruments to explore the poorly understood middle and upper atmosphere, focusing on the processes connecting the various layers and measuring, for the first time, the winds in Jupiter's middle atmosphere. This will expand our knowledge about the transport of energy between various regions of the atmosphere and illuminate the processes behind the longevity of the Great Red Spot and other weather systems. Juice will also explore the magnetosphere of Jupiter in great detail and focus on its interactions with the Galilean moons, especially the processes transporting plasma from Io to the icy moons.[48]
Science instruments
Juice's instrumentsTesting a scale model of Juice's RIME antenna in the Hertz facility, 2023The RIME antenna in stowed configuration. A "selfie" photograph, shortly after launch by JMC2, with Earth in the backgroundThe scalar sub-instrument (MAGSCA), an optical magnetometer with low absolute error, is part of J-MAG
On 21 February 2013, after a competition, 10 science instruments (plus one experiment using the spacecraft's telecommunication system) were selected by ESA, which were developed by science and engineering teams from all over Europe, with participation from the US.[49][50][51][52] Japan also contributed several components for SWI, RPWI, GALA, PEP, JANUS, and J-MAG instruments, and will facilitate testing.[53][54][55]
Jovis, Amorum ac Natorum Undique Scrutator (JANUS)
The name is Latin for "comprehensive observation of Jupiter, his love affairs and descendants."[56] It is a camera system to image Ganymede and interesting parts of the surface of Callisto at better than 400 m/pixel (resolution limited by mission data volume). Selected targets will be investigated in high-resolution with a spatial resolution from 25 m/pixel down to 2.4 m/pixel with a 1.3° field of view. The camera system has 13 panchromatic, broad and narrow-band filters in the 0.36 μm to 1.1 μm range, and provides stereo imaging capabilities. JANUS will also allow relating spectral, laser, and radar measurements to geomorphology and thus will provide the overall geological context.
Moons and Jupiter Imaging Spectrometer (MAJIS)
A visible and infrared imaging spectrograph operating from 0.5 μm to 5.56 μm, with spectral resolution of 3–7 nm, that will observe tropospheric cloud features and minor gas species on Jupiter and will investigate the composition of ices and minerals on the surfaces of the icy moons. The spatial resolution will be down to 75 m (246 ft) on Ganymede and about 100 km (62 mi) on Jupiter.[57]
UV Imaging Spectrograph (UVS)
An imaging spectrograph operating in the wavelength range 55–210 nm with spectral resolution of <0.6 nm that will characterise exospheres and aurorae of the icy moons, including plume searches on Europa, and study the Jovian upper atmosphere and aurorae. Resolution up to 500 m (1,600 ft) observing Ganymede and up to 250 km (160 mi) observing Jupiter.
Sub-millimeter Wave Instrument (SWI)
A spectrometer using a 30 cm (12 in) antenna and working in 1080–1275 GHz and 530–601 GHz with spectral resolving power of ~107 that will study Jupiter's stratosphere and troposphere, and the exospheres and surfaces of the icy moons.
Ganymede Laser Altimeter (GALA)
A laser altimeter with a 20 m (66 ft) spot size and 10 cm (3.9 in) vertical resolution at 200 km (120 mi) intended for studying topography of icy moons and tidal deformations of Ganymede.
Radar for Icy Moons Exploration (RIME)
An ice-penetrating radar working at frequency of 9 MHz (1 and 3 MHz bandwidth) emitted by a 16 m (52 ft) antenna; will be used to study the subsurface structure of Jovian moons down to 9 km (5.6 mi) depth with vertical resolution up to 30 m (98 ft) in ice.
Juice-Magnetometer (J-MAG)
Juice will study the subsurface oceans of the icy moons and the interaction of Jovian magnetic field with the magnetic field of Ganymede using a sensitive magnetometer.
Particle Environment Package (PEP)
A suite of six sensors to study the magnetosphere of Jupiter and its interactions with the Jovian moons. PEP will measure positive and negative ions, electrons, exospheric neutral gas, thermal plasma and energetic neutral atoms present in all domains of the Jupiter system from 1 meV to 1 MeV energy.
Radio and Plasma Wave Investigation (RPWI)
RPWI will characterise the plasma environment and radio emissions around the spacecraft, it is composed of four experiments: GANDALF, MIME, FRODO, and JENRAGE. RPWI will use four Langmuir probes, each one mounted at the end of its own dedicated boom and sensitive up to 1.6 MHz, to characterize plasma, and receivers in the frequency range 80 kHz to 45 MHz to measure radio emissions.[58] This scientific instrument is somewhat notable for using Sonic the Hedgehog as part of its logo.[59][60]
Gravity and Geophysics of Jupiter and Galilean Moons (3GM)
3GM is a radio science package comprising a Ka transponder and an ultrastable oscillator.[61] 3GM will be used to study the gravity field at Ganymede (up to 10 degrees), to determine the extent of internal oceans on the icy moons, and to investigate the structure of the neutral atmospheres and ionospheres of Jupiter (0.1 – 800 mbar) and its moons. 3GM carries an Israeli-built atomic clock "that will measure tiny vacillations in a radio beam".[62][63]
Planetary Radio Interferometer and Doppler Experiment (PRIDE)
The experiment will generate specific signals transmitted by Juice's antenna and received by very-long-baseline interferometry to perform precision measurements of the gravity fields of Jupiter and its icy moons.
^"木星氷衛星探査衛星 JUICE – 日本が JUICE で目指すサイエンス" [Jupiter Ice Moon Exploration Satellite JUICE – Science that Japan is aiming for with JUICE] (PDF). JAXA. Archived from the original(PDF) on 12 November 2019. Retrieved 14 April 2023.
^Shapira, Aviv; Stern, Avinoam; Prazot, Shemi; Mann, Rony; Barash, Yefim; Detoma, Edoardo; Levy, Benny (2016). "An Ultra Stable Oscillator for the 3GM experiment of the JUICE mission". 2016 European Frequency and Time Forum (EFTF). pp. 1–5. doi:10.1109/EFTF.2016.7477766. ISBN978-1-5090-0720-2. S2CID2489857.
Missions are ordered by launch date. Sign † indicates failure en route or before intended mission data returned. ‡ indicates use of the planet as a gravity assist en route to another destination.
Missions are ordered by launch date. † indicates failure en route or before any data returned. ‡ indicates use of the planet as a gravity assist en route to another destination.
Launches are separated by dots ( • ), payloads by commas ( , ), multiple names for the same satellite by slashes ( / ). Crewed flights are underlined. Launch failures are marked with the † sign. Payloads deployed from other spacecraft are (enclosed in parentheses).
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