Jupiter Icy Moons Explorer

and NASA missions that have visited or will visit Jupiter 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 X-ray telescope ATHENA and the gravitational wave observatory LISA (under the older name NGO). Both unsuccessful mission proposals were selected later and are under development as of 2025. 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. In 2024, Airbus Defence and Space received the Excellence Award from ESA for their work on Juice. By 2023, the mission was estimated to cost ESA 1.5 billion euros ($1.6 billion). == Spacecraft ==

Astrolabe facilities, 2023 (artist's impression) 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 of chemical propellant. The total delta-V capability of the spacecraft is about . 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 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 deployable boom will hold J-MAG and RPWI, a long deployable antenna will be used for RIME. Four booms carry parts of the RPWI instrument. The other instruments are mounted on the spacecraft body, or for 3GM, within the spacecraft bus. == Mission timeline ==

Launch launch of Juice 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 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. After several weeks of attempts to free the instrument, it was successfully deployed on 12 May of the same year. Earth-Moon system 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. 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. Two sensors of the Particle Environment Package (PEP) took pictures and in situ measurements of the charged particle cloud surrounding Earth. 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. 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 and Juice successfully flew by Venus on 31 August 2025, with the closest approach of 5,088 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 3,000 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. 3I/ATLAS observations observations by space probes, September 2025 The interstellar comet 3I/ATLAS, discovered in July 2025 as only the third known interstellar object in the Solar System, made its closest approach to the Sun in October 2025. However, this part of its trajectory, when it was expected to show strong cometary activity, was not visible from Earth-based telescopes as it occurred on the other side of the Sun. In September 2025, ESA expected that of all its interplanetary spacecraft, Juice would have the best conditions for observing the object during its close approach to the Sun. using its cameras, spectrometers, and a particle sensor. ESA was also considering coordinating ultraviolet spectrograph observations with NASA's Europa Clipper. Because Juice had to point its high-gain antenna towards the Sun to act as a heat shield during its travel through the inner Solar System, known as "hot-cruise phase", the data from these observations were not expected to reach Earth before February 2026. The observations were conducted between 2 and 25 November 2025. Thermal constraints were expected to limit the observations for no more than 30 minutes per day with the exception of the Particle Environment Package (PEP) which was commanded to operate for twelve days straight. The final observation schedule included six 45-minute slots and one final 4-hour slot. The observations generated 11.18 Gbits of data. The closest approach between the comet and the spacecraft happened on 4 November 2025. In early December 2025, ESA released a preliminary picture of 3I/ATLAS taken on 2 November 2025 by Juice's Navigation Camera (NavCam). The photo included the comet's coma as well as the plasma and dust tails. The spacecraft entered the "cold-cruise phase" of its flight in mid-January 2026 On 2 April 2026, ESA released first preliminary scientific results from the observations. The MAJIS instrument measured that on 2 November 2025, 3I/ATLAS was releasing 2000 kg of water per second and this amount hadn't diminished significantly in observations 10 days later, on 12 November 2025. The SWI instrument detected that most of the water was being released from the Sun-facing side of the comet and a substantial part of it came from icy dust grains of the coma, and not directly from the nucleus. The UVS images also revealed that the gas and dust from the comet stretched at least 5 million km from the nucleus. The JANUS images revealed faint structures within the comet's coma and two tails. File:Comet 3I-ATLAS shows activity in Juice navigation camera teaser ESA515207 - Comet 3I ATLAS shows activity in Juice navigation camera teaser.png|3I/ATLAS by NavCam File:First glimpse of comet 3I ATLAS from Juice science camera.jpg|3I/ATLAS by JANUS File:Comet 3I-ATLAS seen by Juice’s science camera JANUS ESA519346.gif|3I/ATLAS by JANUS, 5 November 2025 File:JANUS sees Comet 3I-ATLAS at 180 million km ESA519350.png|3I/ATLAS by JANUS (red-green-blue) File:JANUS sees Comet 3I-ATLAS in different colours ESA519349.gif|3I/ATLAS by JANUS (red and violet filters) File:NavCam images of Comet 3I-ATLAS ESA519351.gif|3I/ATLAS by NavCam Cruise towards the 2nd Earth flyby In early March 2026, when Juice no longer needed to use its high‑gain antenna as a Sun shield, ESOC performed a series of planned pointing checkout tests on the spacecraft's instruments, software updates, operations exercises, and commissioning activities. == Trajectory ==

Following the launch, multiple gravity assists are needed to put Juice on a trajectory to Jupiter: • Venus flyby, in August 2025 Gravity assists within the Jovian system include: • 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 == Jupiter mission phases ==

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. == Science objectives ==

view from Galileo 's icy surface, viewed from Galileo imaged by Juno '' images showing Amalthea's irregular shape from Cassini 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. Ganymede and Callisto The main science objectives for Ganymede, and to a lesser extent for Callisto, are: Io Juice will monitor the volcanic activity of Io and study the composition of its surface materials The JANUS camera system will track surface changes at a scale of 6-12 km per pixel, the UVS instrument will attempt to detect sulfur dioxide emissions and auroras, and the PEP instrument will monitor Io's plasma torus. Other moons and Jupiter's rings Juice will carry out distant observations of several inner and outer (irregular) satellites of Jupiter throughout its mission. Juice is expected to provide the first detailed spectrographic images of these moons orbiting inside Io's orbit and contribute to solving the so called "Amalthea's Paradox" referring to the moon's surprisingly low density. 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. These observations are expected to deepen our understanding of the transport of energy between various regions of the atmosphere and the processes behind the longevity of the Great Red Spot and other weather systems. Juice will also conduct detailed studies of Jupiter’s magnetosphere and focus on its interactions with the Galilean moons, especially the processes transporting plasma from Io to the icy moons. == Science instruments ==

, is part of J-MAGOn 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. Japan also contributed several components for SWI, RPWI, GALA, PEP, JANUS, and J-MAG instruments, and will facilitate testing. Jovis, Amorum ac Natorum Undique Scrutator (JANUS) The name is Latin for "comprehensive observation of Jupiter, his love affairs and descendants." 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 on Ganymede and about on Jupiter. UV Imaging Spectrograph (UVS) An imaging spectrograph operating in the wavelength range 55–210 nm with spectral resolution of 7 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 spot size and vertical resolution at 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 antenna; will be used to study the subsurface structure of Jovian moons down to depth with vertical resolution up to 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. This scientific instrument is somewhat notable for using Sonic the Hedgehog as part of its logo. Gravity and Geophysics of Jupiter and Galilean Moons (3GM) 3GM is a radio science package comprising a Ka transponder and an ultrastable oscillator. 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". 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. == See also ==