ESA/JUICE encounters Earth/Moon in 2024: overview of the Moons And Jupiter Imaging Spectrometer (MAJIS) observations

IntroductionESA’s JUpiter Icy Moons Explorer (JUICE) mission was launched on April 14th, 2023 and is now on its way to Jupiter and its icy moons, arriving in 2031. After a Jupiter Touring phase of about 3.3 years, JUICE will change its orbiting body, starting the Ganymede orbit phase in November 2034. The goal of JUICE is to characterize the giant gas planet and its three large moons – Ganymede, Europa and Callisto using observations from a variety of remote sensing, geophysical and in-situ instruments.All science and facility instrument data acquired from the JUICE launch to its end of operations, including the Near Earth Commissioning Phase (NECP) and the Cruise Phase, including the planetary flybys, are planned to be archived in ESA’s Planetary Science Archive (PSA) allowing the long-term preservation of an exceptional data set. The high-level plans of each science team for archive data generation are captured in the Science Data Generation, Validation and Archiving Plan, a living document modified as the mission evolves and authored by instrument teams and the JUICE Science Operations Centre (SOC). Archiving Approach and organizationThe JUICE approach to data archiving follows closely that of the ExoMars Trace Gas Orbiter (TGO) and BepiColombo missions. The data are processed after each ground-station (downlink) pass and archived following the PDS4 standard. The calibrated data are sent by the instrument teams to the PSA. All data will be subject to a 6-month proprietary period before being made public. In addition to following the NASA PDS rules, the data also adhere to PSA cross-mission rules recorded in the PSA PDS4 Archiving Guide (a living document used by all new ESA missions archiving data in the PSA). In practice, the PSA allows for the addition of cross-mission attributes which are not included in the PDS4 core model. In summary, the JUICE products to be archived in the PSA are validated against the PDS, the PSA and the JUICE dictionaries, where the latter capture additional rules related to the mission itself.Additionally, the archive follows the PSA PDS4 structure by having a single bundle per instrument containing collections organised by data type (e.g., document, geometry, data), with science data collections being further subdivided by processing level (e.g., data_raw, data_calibrated, data_derived, …). JUICE Archive StatusThe JUICE Archive is already providing auxiliary data (spacecraft monitoring data) to the community, while defining and archiving the data acquired by the JUICE facility instruments: the JUICE Monitoring Camera (JMC), the RADiation–hard Electron Monitor (RADEM), the High Accuracy Accelerometer (HAA) and the Navigation Camera (NavCam). Since the Lunar-Earth Gravity Assist (LEGA) in August 2024, the non-peer reviewed JMC images are publicly available in the PSA (https://psa.esa.int/). The other facility instrument data are also planned to become public, after successfully passing their archive peer review. RADEM raw data will be the next in line to become publicly available to the scientific community.Simultaneously, iterations between the JUICE Archive Scientists and the Instrument Teams are taking place to define the data products details (data and meta-data content, data structure, product names, etc…) for several JUICE science instruments. The public release of the science instrument (raw and calibrated levels) data (acquired during the cruise phase) in the PSA is planned for mid 2029.

The JUICE (Jupiter Icy Moons Explorer) mission is the first Large (L-class) mission selected for the European Space Agency (ESA) Cosmic Vision 2015-2025 program. Its main goal is the exploration of the Jupiter system and the investigation of its icy Galilean satellites Europa, Ganymede and Callisto [Grasset et al. (2013)]. JUICE has been successfully launched on 14 April 2023 from Europe’s Spaceport in Kourou, French Guiana, on an Ariane 5 launcher and, after its 8 years journey throughout the inner Solar System, it will reach the Jupiter system in July 2031. During its nominal science phase, JUICE will spend many months orbiting around Jupiter, performing fly-bys of Europa, Ganymede and Callisto, and finally conducting an orbital tour of Ganymede. JUICE carries 10 state-of-the-art instruments, comprising the most powerful remote sensing, geophysical and in situ payload suite ever flown to the outer Solar System. Among those, JANUS (Jovis Amorum ac Natorum Undique Scrutator) is the scientific optical camera system [Palumbo et al. (2025)]. Its design has been optimised, according to JANUS’ scientific requirements, for observations of a wide range of targets, from Jupiter’s atmosphere, to solid satellite surfaces and their exospheres, rings, and transient phenomena like lightning.JANUS is a modified Ritchey-Chrétien telescope with a nominal focal length of 467 mm, an effective entrance pupil diameter of 103.6 mm, a FoV of 1.72° x 1.29° and a 2000x1504 pixel CMOS sensor with a pixel dimension of 7 µm. In addition, a filter wheel with 13 filters allows JANUS to acquire multi-spectral images in the 340-1080 nm wavelength range. This camera provides images of the targets with a scale of 7.5 m/pixel at a distance of 500 km. Such characteristics will allow to observe the surfaces of the icy satellites with a spatial resolution ranging from 400 m to 3 m for Europa, Ganymede and Callisto. In addition, Jupiter and other targets, e.g. Io, small moons and rings, will be observed with a resolution from few km to tens of km.The achievement of mission and instrument science goals during the science phase is strictly related to the resources available to each instrument. A series of science planning exercises, led by ESA and involving all JUICE instruments, are taking place during the cruise phase. Starting from individual instrument timelines, sets of observations that are fulfilling specific scientific objectives, under ESA's coordination, a harmonization process integrates proposed observations from various payloads into a unified mission timeline. ORB17 was the chosen mission segment for the fourth planning exercise and a very challenging one: it is a multi-target scenario over a Medium-Term-Planning (MTP) time scale. MTP time scales of several weeks will be typical during the JUICE science phase at Jupiter, and in that sense this exercise was a huge step forward in developing and testing realistic planning sequences, compared to the more focused planning intervals of past exercises. ORB17 is a highly representative orbit from the 3rd Phase of the JUICE mission, during which the inclination of the spacecraft orbit gradually increases to >30° with the help of multiple Callisto flybys. Phase-3 orbits thus offer repeated opportunities to observe the polar regions of the planet during perijoves, offer a top-down perspective on the rings and the Europa and Io torus, and allow for repeated close observations of Callisto. Specifically, ORB17 planning covered a three-week period (2032-12-18 to 2033-01-08), and included the Callisto flyby 16C9 at a low altitude on the leading hemisphere of the moon and a perijove at high south latitudes. ORB17 planning was successful: Callisto’s surface at the flyby and Jupiter’s atmosphere during perijove could get sufficient observation time. Even more important was that the observation time was accumulated while also finding common or shared pointing strategies with several instruments during perijove and during most of the Callisto flyby period (JANUS, MAJIS, SWI, UVS, PEP-Lo, PEP-Hi, RIME). Common strategies and resolutions will likely propagate as planning templates in follow up exercises, maximizing the efficiency of science planning for JANUS and JUICE overall. An effort will have to be put on optimizing conflicting periods, especially during closest approach of moon flybys, which present most of the challenges for incorporating all instrument pointing requirements and resource allocation.Here we present the JANUS perspective of the ORB17 planning, with a view to the actions that shall be taken in the future to ensure that all science goals will be reached in the science phase. Acknowledgements: JANUS has been funded by the respective Space Agencies: ASI (lead funding agency), DLR, Spanish Research Ministry and the UK Space Agency. Main hardware-provider Companies and Institutes are Leonardo SpA (Prime Industry), DLR-Berlin, CSIC-IAA and Sener. PI and Italian team members acknowledge ASI support in the frame of ASI-INAF agreement n. 2023-6-HH.0.

Launched in April, 2023, ESA’s JUpiter ICy moons Explorer (JUICE) is en route to the Jupiter system. Upon arrival in 2031, the spacecraft will orbit Jupiter for 3.5 years, making 35 total encounters with Ganymede, Europa, and Callisto, before going into orbit about Ganymede for 1 year.  NASA’s Europa Clipper is scheduled to launch in October 2024, and arrives in the Jupiter system in 2030, a year before JUICE. Orbiting Jupiter, the Clipper spacecraft will spend a year in the system before focusing on ~52 flybys of Europa during a nominal four-year primary mission phase, while also making multiple serendipitous flybys of Ganymede and Callisto. Having two highly instrumented spacecraft in close proximity in time and space affords unprecedented opportunities for synergistic observations of Europa, Ganymede, Callisto, Io, Jupiter’s atmosphere, magnetosphere and environment, and Jupiter’s small satellites and rings, as well as opportunities for unique heliospheric and magnetosphere science during the JUICE and Clipper missions’ cruise and Jupiter-approach phases.Analysis of potential joint science opportunities is underway by a small team of scientists from the JUICE and Clipper mission teams. Ideas have been collated from JCSC members as well as from three joint Clipper-JUICE workshops (2018, 2019, 2022), and the Science Traceability Matrix from a prior joint ESA-NASA study, the Europa Jupiter System Mission (EJSM). We recently produced a report on science that can be accomplished during the two spacecrafts’ cruise and Jupiter approach phases (Bunce et al., this meeting), and are now investigating potential opportunities once JUICE and Clipper are in orbit around Jupiter. Multiple opportunities exist for joint science at several different targets within the Jovian system, including two opportunities near Europa where the spacecraft are within 0.5Rj of each other and only a few hours apart. Scientific objectives may fall into one or more categories: (1) time dependent, in which both spacecraft must acquire data at same time, or one spacecraft’s observations inform the other’s observations; (2) space dependent, in which each spacecraft acquires data from specific parts of the Jovian system, or both observe the same target with similar, or different viewing geometries; and (3) an increase in science data (e.g. temporal or spatial coverage) made possible due to the availability of additional instrument types or data collection opportunities.There are currently no firm commitments from NASA or ESA to accomplish science beyond that of each mission’s primary science objectives. However, discussions are ongoing and we are optimistic that our recommendations for the unprecedented opportunities afforded by the two missions’ alignment will enable funding support to be found. In this paper, we discuss some of the potential combined science from JUICE and Clipper that could further enhance understanding of the of the Jupiter system and the origin and habitability of the Galilean moons.

We use Spacecraft Plasma Interaction Software (SPIS) simulations of the surface charging of the Jupiter Icy Moons Explorer (JUICE) spacecraft to study how the variable magnetospheric environment of Jupiter will impact the future JUICE particle and electric field measurements. The study has been limited to the magnetospheric region relevant for JUICE, that is, the environments of the inner and middle magnetosphere of Jupiter. The closest approach of Jupiter will be at 9.3 RJ. In the inner magnetosphere the spacecraft will charge a few volts negative for the typical plasma sheet environment, where ne,cold ≈ 50 cm-3 and Te,cold ≈ 20 eV. However, Galileo detected plasma densities of up to 600 cm-3 in the region around 9.4 RJ (Kurth et al., 2001). These densities could be due to activity on Europa, such as plumes, or a local disturbance of cold and dense iogenic plasma (Bagenal et al., 2015). Such high densities could result in surface potentials of tens of volts, when assuming Te,cold ≈ 5 eV, which would inhibit cold electron measurements performed by the electron spectrometer of JUICE, since the electrons would be repelled before reaching the detector. In addition, the large differential charging of tens of volts, due to the dielectric surfaces, would disturb electric field measurements. However, the cold electron temperature is not well constrained for this particular disturbance and a lower plasma temperatures would decrease the magnitude of the surface potential. Our SPIS simulations show surface potentials of a few volts positive for typical magnetospheric environments in the plasma sheet between 15 and 26 RJ, where ne,cold > 20 ne,hot and the hot electron component range from 1-5 keV. However, Galileo measurements occasionally show hot electron densities equal to or slightly larger than the typical cold electron densities (Futaana et al., 2018). Simulated surface potentials, using ne,cold ≈ ne,hot, show no significant difference compared to the typical environment since the increase in hot electrons is counterbalanced by the increase in the production of secondary electrons. In this particular environment, higher electron densities will charge the spacecraft more negative while higher secondary electron production will charge the spacecraft more positive. Assuming Maxwellian distributions, we obtain that an unusually dense hot, 1-5 keV, electron component, like the one measured by Galileo, would not disturb the particle measurements of JUICE. Our study shows that the absolute charging of the spacecraft strongly depends on the cold electron density and temperature, and, for certain environments, on the spacecraft orientation relative to the plasma flow and the solar radiation. An unusually dense and hot, 1-5 keV, electron plasma component will not have a substantial impact on the charging, in the studied region. We are investigating whether different energy distributons will change this conclusion. The SPIS JUICE surface charging simulation results show that only minor perturbations will be obtained in typical Jovian magnetospheric environments, while substantial perturbations will occasionally occur in the disturbed magnetosphere.

Jupiter and its icy moons—Europa, Ganymede, and Callisto—are among the most intriguing targets in the Solar System for studying habitability and searching for life. Substantial evidence suggests that these moons harbor subsurface water oceans beneath their icy crusts, with conditions that may support the development and sustainability of life. To investigate this, the European Space Agency (ESA) has launched the JUpiter ICy moons Explorer (JUICE) on April 14th, 2023.The Jovian radiation environment is extremely hazardous for space exploration. High-energy electrons trapped in the Jovian system can penetrate thick shielding walls and accumulate large doses in electronic components and materials reducing their operational lifespan significantly. High energy particles can also disassociate biological molecules that migrated from the icy moons’ oceans to the surface hindering the detection of biosignatures from orbit.For these reasons, JUICE carries a RADiation hard Electron Monitor (RADEM), with a novel design, capable of measuring high energy electrons, protons, and ions. RADEM is an engineering instrument, that is continuously operated throughout the mission including its cruise phase, but that can also contribute significantly to scientific investigations of the Jovian system. The same is true for the cruise phase. JUICE joins an increasing but still limited Solar fleet that includes STEREO-A, Solar Orbiter, Parker Solar Probe, BepiColombo, and near-Earth spacecraft, having already observed dozens of Solar Energetic Particle events.In this work, we will take a deep dive into the two first years of RADEM observations, calibration activities, and scientific highlights, including a cosmic ray calibration campaign, cross-calibrations with STEREO-A and SOHO, and observation of the Van Allen belts during JUICE’s world first Lunar-Earth Gravity Assist.

Launched in April, 2023, ESA’s JUpiter ICy moons Explorer (JUICE) is now two years into its journey to the Jupiter system. Upon arrival in 2031, the spacecraft will orbit Jupiter for 3.5 years, making 35 total encounters with Ganymede, Europa, and Callisto, before going into orbit about Ganymede for 1 year.  NASA’s Europa Clipper successfully launched in October 2024, and arrives in the Jupiter system in 2030, more than a year before JUICE. Orbiting Jupiter, the Clipper spacecraft will spend a year in the system before focusing on ~52 flybys of Europa during a nominal three-year primary mission phase, while also making multiple serendipitous flybys of Ganymede and Callisto.A preliminary analysis of potential joint science opportunities has been conducted by a small team of scientists from the JUICE and Clipper mission teams. Ideas have been collated from JCSC members as well as from three joint Clipper-JUICE workshops (2018, 2019, 2022), and the Science Traceability Matrix from a prior joint ESA-NASA study, the Europa Jupiter System Mission (EJSM). We have produced two reports on science that can be accomplished during the two spacecrafts’ cruise and Jupiter approach phases, and potential opportunities once JUICE and Clipper are both in orbit around Jupiter. For the former, we note that cruise represents a rare occasion for joint measurements of interplanetary space between the orbits of Mars and Jupiter, and an unprecedented opportunity for an upstream solar wind monitor (JUICE) during approach to the Jupiter system once Clipper is already orbiting Jupiter.  For the latter, we find that the presence of two flagship-class, well-instrumented spacecraft in the Jovian system during the same 4.3 year period affords extraordinary opportunities to increase the science return beyond that possible from each mission alone. Joint observations are possible of all four Galilean satellites, the Jovian rings and small satellites, Jupiter’s atmosphere, and the magnetosphere. 100 potential joint science objectives have been identified, of which 50 are considered high priority. These include many synergistic measurements; some which would take place contemporaneously, and some measurements that are coordinated but asynchronous; and many complementary objectives such as cross-calibration of instruments and also serendipitous opportunities. The data return would be further enhanced by coordination with ground- or space-based assets during some of the measurements.There are currently no firm commitments from NASA or ESA to accomplish science beyond that of each mission’s primary science objectives. However, discussions continue and we are hopeful that our recommendations for the opportunities afforded by the two missions’ alignment will enable resource support to be found.

The Jupiter Icy Moons Explorer (JUICE) mission is the first Large (L-class) mission selected for the European Space Agency (ESA) Cosmic Vision 2015-2025 program. It is devoted to exploring the Jupiter system and investigating its icy Galilean satellites Europa, Ganymede and Callisto [Grasset et al., (2013)]. JUICE has been succesfully launched on 14 April 2023 from Europe’s Spaceport in Kourou, French Guiana, on an Ariane 5 launcher and, after its 8 years journey throughout the inner Solar System, it will reach the Jupiter system in July 2031. During its nominal science phase, JUICE is planned to spend many months orbiting around Jupiter, performing fly-bys of Europa, Ganymede and Callisto, and finally conducting an orbital tour of Ganymede.JUICE carries 10 state-of-the-art instruments, comprising the most powerful remote sensing, geophysical and in situ payload suite ever flown to the outer Solar System. Among those, JANUS (Jovis Amorum ac Natorum Undique Scrutator) is the scientific optical camera system [Palumbo et al., (2014)]. Its design has been optimised, according to JANUS’ scientific requirements, for observations of a wide range of targets, from Jupiter’s atmosphere, to solid satellite surfaces and their exospheres, rings, and transient phenomena like lightning.JANUS is a modified Ritchey-Chrétien telescope. It has a nominal focal length of 467 mm, an effective entrance pupil diameter of 103.6 mm, a FoV of 1.72°x1.29° and a 2000x1504 pixel CMOS sensor with a pixel dimension of 7 µm. In addition, a filter wheel with 13 filters allows JANUS to obtain multi-spectral images in the 340-1080 nm wavelength range. This camera provides images of the targets with a scale of 7.5 m/pixel at a distance of 500 km. Such characteristics will allow to observe the surfaces of the icy satellites with a spatial resolution ranging from 400 m to 3 m for Europa, Ganymede and Callisto. In addition, Jupiter and other targets, e.g.  Io, small moons and rings, will be observed with a resolution from few km to tens of km.The achievement of mission and instrument science goals during the science phase is strictly related to the resources available to each instrument. A series of science planning exercises, lead by ESA and involving all instruments, are taking place during the cruise phase. Starting from individual instrument timelines, sets of observations that are fulfilling specific scientific objectives, under ESA's coordination, a harmonization process integrates proposed observations from various payloads into a unified mission wise timeline. The outcome of the planning exercises is the identification of the available resources (and in particular of pointing, data volume and power) during each scenario and the definition of the best observation approach which ensures the best scientific outcome at instrument and mission level for each scientific target.Here we present the JANUS planning strategy that we have developed for Jupiter’s atmosphere observations in the framework of the Perijove 12 (PJ12) planning exercise. A detailed science planning is pivotal to assess the capabilities of the instrument and estimate the resources required to achieve the JANUS and JUICE science goals, identify the best observation approach which is in line with the available resources. Acknowledgement: authors acknowledge support from National Space Agencies (ASI*, DLR, Spanish Research Ministry and UKSA) in the frame of JANUS-JUICE project.* ASI-INAF agreement n. 2023-6-HH.

This article presents the first study of the interaction between the Jupiter Icy Moons Explorer (JUICE) spacecraft and the solar wind environment at 1 AU. The state‐of‐the‐art software Spacecraft Plasma Interaction Software was used to simulate the surface charging of the spacecraft and the altered particle environment around the spacecraft. The simulations show that for a typical solar wind environment the spacecraft will charge to around 6 V, with the different dielectric parts of the spacecraft charging to potentials from around −36 to 8 V. For the studied extreme solar wind environment, similar to the environment found in the sheath region inside the shock front of an Interplanetary Coronal Mass Ejection, the surface potential of the spacecraft is lower due to the increased accumulation of electrons. The spacecraft will charge to around 3 V, with the different dielectric surfaces charging from around −45 to 9 V. We also show how the interaction between the spacecraft and its environment alters the ion and electron particle environment around the spacecraft. This study is the first step toward developing correction techniques for the impact that the interaction between the JUICE spacecraft and its environment has on the JUICE charged particle and field measurements.

Launched on 14 October 2024, the Europa Clipper mission represents a pivotal endeavor in planetary exploration, aimed specifically at studying the habitability of Jupiter’s moon Europa. During its cruise phase, the spacecraft will conduct gravity assist maneuvers at both Mars and Earth before arriving in the Jovian system in 2030, where it is scheduled to perform a series of 49 flybys of Europa, along with additional encounters with Ganymede and Callisto. These gravity assists are instrumental in refining the spacecraft’s trajectory and optimizing the calibration of some of its scientific instruments prior to the primary mission phase, underscoring the importance of the cruise period as a preparatory stage for the core observational efforts.The Mars gravity assist on 1 March 2025 provided an opportunity to calibrate and test three Europa Clipper investigations. First, the Europa Thermal Emission Imaging System (E-THEMIS) thermal instrument acquired data on Mars as a well characterized source, to test an algorithm that corrects a nonlinearity in one of the instrument’s wavelength bands. These observations occurred one day prior to closest approach and near in time when the same region was measured by the THEMIS instrument on Mars Odyssey, which is heritage for E-THEMIS. Second, the Radar for Europa Assessment and Sounding: Ocean to Near-surface (REASON) ice-penetrating radar performed its first comprehensive end-to-end test by operating at closest approach. Due to technical limitations and flow of the flight system integration process, it was not possible to complete such test prior to launch. As a reference for comparison, the Shallow Radar (SHARAD) sounder on the Mars Reconnaissance Orbiter (MRO), which is heritage for REASON, obtained data of the same area 20 minutes later. Finally, the Gravity and Radio Science (G/RS) team tested flyby procedures and processes using the open-loop receivers of the Deep Space Network (DSN). At the time of writing of this abstract, the E-THEMIS and REASON data have not been received due to limitation in the bandwidth of the spacecraft communication. The data are anticipated to be transmitted to ground by June 2025.The Earth gravity assist will occur on 3 December 2026. This encounter will enable the one and only absolute calibration of the Europa Clipper Magnetometer (ECM) post launch by flying through Earth’s well-characterized magnetic environment. Existing space assets near Earth will also allow for cross-calibration of the Plasma Instrument for Magnetic Sounding (PIMS) through comparison of observed charged particles populations, which are difficult to faithfully reproduce in a laboratory environment prior to launch. Additional instrument operations are presently under discussion. While these observations are not critical to the functioning of the payload, the Earth encounter offers a unique opportunity for the mission operations team to test simultaneous operation of multiple instrument and flight system components in preparation for the primary mission.Finally, throughout the cruise phase, the mission’s scientific instruments must be exercised periodically to verify functionality and for calibrations purposes. For select instruments, notably ECM and PIMS, these operations enable the collection of complementary data of their heliospheric and magnetospheric environment as the spacecraft transitions through varying interplanetary conditions. The coordination of the Europa Clipper mission with the European Space Agency’s Jupiter Icy Moons Explorer (JUICE) has further created unique opportunities for joint interactive science during the joint cruise phase and beyond. Such collaboration could potentially enhance our understanding of broader dynamics in the solar wind and within the Jovian system while employing complementary observational strategies.Collectively, the planned and already executed activities during the cruise phase of the Europa Clipper mission will set the stage for detailed analysis upon arrival in the Jovian system, ultimately enhancing our understanding of one of the solar system’s foremost candidates for habitability. At Europa, the anticipated scientific observations will include characterizing the ice shell and subsurface ocean properties, determining the surface and atmospheric composition, and understanding the formation of geological features at the surface. A well-working and fully calibrated payload is a prerequisite for achieving these science objectives and the mission’s overarching goal to investigate Europa’s habitability.

The JUpiter ICy moons Explorer (JUICE), the European Space Agency’s first large-class mission under the Cosmic Vision 2015–2025 program, is dedicated to exploring the potential habitability of Jupiter’s icy moons: Europa, Callisto, and Ganymede. Launched on April 14, 2023, JUICE is currently in an 8-year cruise phase to Jupiter, utilizing gravity assists from Venus, Earth, and the Moon. Notably, JUICE is the first spacecraft to execute a Lunar-Earth gravity assist (LEGA), which was successfully completed in August 2024. This maneuver provided a critical trajectory adjustment while also allowing several onboard instruments to operate during the flyby.Shortly after the Moon gravity assist, JUICE experienced an unforeseen acceleration attributed to an outgassing event. During the LEGA, radiometric observables, including Doppler and ranging data in the X-band, were collected by ESA’s New Norcia deep space station. These measurements were analyzed to characterize the outgassing-induced delta-V acting on JUICE. The analysis involved reconstructing the outgassing event and comparing it with models. The characterization of this event using radiometric data provides insights that complement measurements from other onboard instruments. For instance, the spacecraft’s reaction wheels recorded an excess torque as they compensated for the perturbation to maintain attitude control. The High-Accuracy Accelerometer (HAA), the Particle Environment Package (PEP), and the Submillimetre Wave Instrument (SWI) also captured data related to the outgassing event, enhancing its overall characterization.In this work, we analyze radiometric measurements to provide a detailed quantification of the magnitude and orientation of the outgassing force during the flyby. These findings improve our understanding of non-gravitational forces affecting JUICE and contribute to refining our knowledge of the spacecraft's dynamical environment.

ESA’s JUpiter ICy moons Explorer (JUICE) launched on April 14, 2023, beginning an eight-year journey to the Jupiter system. Arriving in 2031, JUICE will make 35 total flybys of Ganymede, Europa, and Callisto before going into orbit about Ganymede. NASA’s Europa Clipper is scheduled to launch in October 2024, arriving in the Jupiter system in 2030, a year ahead of JUICE. Clipper will spend a year in the system before undertaking 49 flybys of Europa during a nominal three-year primary mission phase, while also making multiple serendipitous flybys of Ganymede and Callisto. Having two highly instrumented spacecraft in close proximity in time and space affords unprecedented opportunities for synergistic observations during the missions’ main orbital phases, and unique heliospheric and magnetosphere science during cruise and Jupiter approach. While there are currently no firm commitments from NASA or ESA to accomplish science beyond that of each mission’s primary science objectives, discussions are ongoing and the task of the appointed JUICE-Clipper Steering Committee (JCSC) is to provide recommendation of compelling joint science opportunities between the two missions. This paper will focus on the cruise and Jupiter approach phases. We have identified a number of potential opportunities for investigating the evolution of the solar wind plasma and interplanetary magnetic field and related structures such as monitoring Coronal Mass Ejections (CMEs) or Corotating Interaction Regions (CIRs) during times when the two spacecraft are radially aligned (i.e. at similar heliocentric longitudes) or at similar heliocentric distances, as well as radio science observations of the solar wind and/or Solar Energetic Particle (SEP) events that could be observed throughout interplanetary transfer. There is also potential for investigating the evolution of solar wind structures and disturbances when both spacecraft are “connected” through Parker Spiral field lines. The cruise science return from JUICE and Clipper could be further enhanced by data from other operational spacecraft (e.g., BepiColombo, Solar Orbiter, Parker Solar Probe, MAVEN, IMAP, Psyche), thus expanding the catalogue of opportunities for these identified configurations, as well as simultaneous observations by ground and space-based observatories (e.g., JWST, Keck, etc.). The >1 year Jupiter approach phase of the JUICE spacecraft while Clipper orbits within the jovian magnetosphere provides an unrivalled opportunity to study the complexity of the solar wind-magnetosphere interaction and aurora at Jupiter, a topic where there remain many open questions. This phase would provide a unique opportunity for preparatory joint observations to understand if and how the solar wind influences the moon’s local space environment, and the related interaction with Jupiter’s rapidly rotating magnetosphere.

The CIS115 is a Teledyne-e2v CMOS image sensor with 1504 × 2000 pixels of 7 μm pitch. It has a high optical quantum efficiency owing to a multi-layer anti-reflective coating and its backside illuminated construction, and low dark current due to its pinned photodiode 4T pixel architecture. The sensor operates in rolling shutter mode with a frame rate of up to 7.5 fps (if using the whole array), and has a low readout noise of ∼5 electrons rms. The CIS115 has been selected for use within the JANUS instrument, which is a high resolution camera due to launch on board ESA's JUpiter ICy moons Explorer (JUICE) spacecraft in 2022. After an interplanetary transit time of over 7 years, JUICE will spend 3.5 years touring the Jovian system, studying three of the Galilean moons in particular: Ganymede, Callisto and Europa. During this latter part of the mission, the spacecraft and hence the CIS115 sensor will be subjected to the significant levels of trapped radiation surrounding Jupiter. Gamma and proton irradiation campaigns have therefore been undertaken in order to evaluate both ionising and non-ionising dose effects on the CIS115's dark current performance. Characterisations were carried out at expected mission operating temperatures (−35 ± 10̂C) both prior to and post-irradiation. Models of the resulting degradation in dark current behaviour will be combined with expected doses during the JUICE mission in order to predict the performance of the CIS115 at the mission end-of-life.

The JUpiter Icy Moon Explorer (JUICE) mission, launched on 14 April 2023, aims to explore Jupiter and its Galilean moons, with arrival in the Jovian system planned for mid-2031. One of the scientific investigations is the Geodesy and Geophysics of Jupiter and the Galilean Moons (3GM) radio science experiment, designed to study the interior structures of Europa, Callisto, and Ganymede and the atmospheres of Jupiter and the Galilean moons. The 3GM experiment employs a Ka-band Transponder (KaT) to enable two-way coherent range and Doppler measurements used for the gravity experiment and an Ultra Stable Oscillator (USO) for one-way downlink occultation experiments. This paper analyzes KaT data collected at the ESA/ESTRACK ground station in Malargüe, Argentina, during the Near-Earth Commissioning Phase (NECP) in May 2023 and the first in-cruise payload checkout (PC01) in January 2024. The radiometric data were fitted using both NASA’s Mission Analysis, Operations, and Navigation Toolkit Environment (MONTE) and ESA’s General Orbit Determination and Optimization Toolkit (GODOT) software. The comparison of the orbital solutions showed an excellent agreement. In addition, the Doppler and range residuals allowed a preliminary assessment of the quality of the radiometric measurements. During the NECP pass, the radio link data showed a range-rate noise of 0.012 mm/s at 1000 s integration time, while the root mean square of the range residuals sampled at 1 s was 8.4 mm. During the first payload checkout, the signal power at the KaT input closely matched the value expected at Jupiter, due to a specific ground station setup. This provided early indications of the 3GM’s performance during the Jovian phase. In this test, the accuracy of range data at an integration time of 1s, particularly sensitive to the link signal-to-noise ratio, degraded to 13.6 cm, whilst the range-rate accuracy turned out to be better than 0.003 mm/s at 1000 s, thanks to the accurate tropospheric delay calibration system (TDCS) available at the Malargue station (inactive during NECP).

The RADiation–hard Electron Monitor (RADEM) is an instrument on board the ESA JUpiter ICy moons Explorer (JUICE) deep-space mission launched on April 14th, 2023. As a part of the Cosmic Vision program, RADEM on JUICE will spend over three years exploring the radiation environment of the Jovian system, including its icy moons Ganymede, Callisto, and Europa. The instrument serves as an on-board radiation monitor, providing nonstop information on particle fluxes and their energy spectra. In addition to being a platform subsystem relevant to spacecraft safety and health, RADEM obtains scientifically valuable data on the radiation environment and extends the particle detection range covered by the JUICE Particle Environment Package (PEP) instrument suite to much higher energies, and broadens the energy coverage in the tens to hundreds of MeV range for electrons and protons, compared to past missions. RADEM consists of three detector subunits: the Electron Detector Head, the Proton & Heavy Ion Detector Head, and the Directional Detector Head. Each of them is connected to a separate readout electronics with a dedicated front-end Application–Specific Integrated Circuit (ASIC) designed especially for the JUICE mission. RADEM measures electrons in the 0.3–40 MeV energy range, protons in the 5–250 MeV energy range, and heavy ions within the Linear Energy Transfer range from 0.1 to 10 MeV cm mg−1. The Directional Detector provides an angular coverage of incoming radiation up to about 35% of the sky. Being a platform device, the monitor operates and delivers data permanently. Therefore, RADEM measurements also cover the radiation environment of the interplanetary space during the mission cruise phase, including long-term studies of the environment between Venus and Mars as well as the detection of the Solar Energetic Particle events that propagate across different locations in the Solar System.

The ESA’s Jupiter Icy moons Explorer (JUICE) L-class mission is devoted to the study of the Jovian system.It will be launched in 2023 and, after an 8-year cruise phase (with 3 gravity assists to Earth and 1 to Venus), will start a tour of the Galilean moons that will last 3.2 years.The onboard Geodesy and Geophysics of Jupiter and the Galilean Moons (3GM) radio science experiment will accomplish a detailed study of Europa, Ganymede and Callisto thanks to a state-of-the-art radio tacking system. 3GM will rely on a multi-frequency link enabled by two onboard units: the Ka-band Transponder (KaT) payload (establishing a full 2-way link in Ka band) and the Deep Space Transponder (DST), enabling 2-way coherent X/X and X/Ka link used for telemetry and telecommand. The multi-frequency link allows accurate measurements of range (≈1-4 cm @60s) and range rate (≈0.003 mm/s @1000s) at nearly all Sun-probe-Earth angles.The data achieved during the tour phase (2 flybys at Europa and 21 flybys at Callisto) will be used to estimate the Europa’s quadrupole gravity field and Callisto’s static gravity field to at least degree and order 7 and its tidal Love number k2 with an accuracy of ~0.06 [1]. This will allow 3GM to detect the presence or absence of a subsurface ocean underneath the ice shell of Callisto.At the end of the tour phase, JUICE will be the first spacecraft to orbit around and icy satellite, allowing a comprehensive study of the moon. The Ganymede 9-month orbital phase is composed of a 5-month elliptical orbit followed by a 4-month circular orbit at 500 km of altitude (GCO-500). The mission could be extended for a 200 km altitude campaign if the residual propellant will be sufficient to decrease the orbital radius.Range and Doppler data achieved by 3GM during the GCO-500 will be used to infer the static (up to degree 35-45) gravity field, the rotational state, and the tidal response of Ganymede.Ganymede’s k2 is subject to time-varying tides due to Jupiter, Io, Europa and Callisto. In particular, the Ganymede’s gravitational perturbations due to the satellites has a high spectral content. This signal can be used to estimate k2 at a set of frequencies, up to 4d-1. The profile of k2 as a function of the frequency, due to the subsurface ocean, is expected to show a peak at a certain resonance frequency, its value being strictly related to the ocean’s depth. We show that the accuracy of the 3GM radio science data is sufficient to detect the peak, if present, and measure its amplitude. In this case the ocean thickness can be estimated with a 7% uncertainty [2].