Space Science Reviews

Based on decades of single-spacecraft measurements near 1 au as well as data from heliospheric and planetary missions, multi-spacecraft simultaneous measurements in the inner heliosphere on separations of 0.05–0.2 au are required to close existing gaps in our knowledge of solar wind structures, transients, and energetic particles, especially coronal mass ejections (CMEs), stream interaction regions (SIRs), high speed solar wind streams (HSS), and energetic storm particle (ESP) events. The Mission to Investigate Interplanetary Structures and Transients (MIIST) is a concept for a small multi-spacecraft mission to explore the near-Earth heliosphere on these critical scales. It is designed to advance two goals: (a) to determine the spatiotemporal variations and the variability of solar wind structures, transients, and energetic particle fluxes in near-Earth interplanetary (IP) space, and (b) to advance our fundamental knowledge necessary to improve space weather forecasting from in situ data. We present the scientific rationale for this proposed mission, the science requirements, payload, implementation, and concept of mission operation that address a key gap in our knowledge of IP structures and transients within the cost, launch, and schedule limitations of the NASA Heliophysics Small Explorers program.

Here we review the origin, evolution, and compositional properties of Saturn’s ring moons. This class of eleven small satellites includes objects orbiting near the outer edge of the main rings (Pan, Daphnis, Atlas, Prometheus, Pandora, Janus, Epimetheus) and “ring-embedded” moons (Aegeon, Methone, Anthe, Pallene) orbiting inward of Enceladus and associated with either diffuse or partial rings. We discuss current formation scenarios, according to which ring moons could originate either in the main rings from accretion onto original seeds denser than the ring material, or outside the A ring from spontaneous accretion of ring particles, and then evolve outwards due to gravitational torque from the rings. Remote sensing observations of the ring moons from the Cassini mission are analyzed in the broader context of Saturn’s icy moons and main rings observations. Spectroscopic data support a compositional paradigm similar to the main rings, dominated by water ice, and smaller amounts of two separate contaminants, in the form of a UV absorber and a spectrally neutral darkening material. Global radial trends in the spectral properties of the ring moons suggest that the surface composition is significantly affected by a complex interplay of exogenous processes, among which the contamination from nearby A ring particles, meteoritic bombardment, charged particle flux, and E ring particle accumulation, depending on the corresponding magnitude at the ring moon orbital distance and exposure time. These processes modify the original composition inherited by the rings and, coupled with the fact that the surface composition is likely representative only of the ring moon outer layers, make it difficult to trace back the present composition to a given ring moon formation scenario.

Accurate determination of the ionospheric parameters is one of the important objectives of the Ionospheric Connection Explorer (ICON) mission. Recent analyses of the current ICON Level 2.5 (L2.5) data product have shown that the ionospheric parameters (e.g., the peak electron density, \(n_{\mathrm{m}}F_{2}\) , and the peak height, \(h_{\mathrm{m}}F_{2}\) ) that are retrieved from the nighttime OI 135.6 nm emission observed by ICON’s Far Ultraviolet (FUV) imager exhibit a systematic bias when compared to external radio measurements. In this study, we demonstrate that the bias was introduced by Tikhonov regularization that was used for the FUV Level 1 data inversion to generate the L2.5 data product. To address the bias, we develop a Bayesian framework for accurate determination of the nighttime ionospheric parameters through the Maximum A Posteriori (MAP) estimation. We show through analysis of synthetic observations that the key to an accurate MAP estimation is to construct a series of prior distributions associated with different \(h_{\mathrm{m}}F_{2}\) using climatological empirical models. Implementation of the MAP estimation with this series of prior distributions to the ICON FUV observations and comparison of the ionospheric retrievals with external radio measurements verify that the Bayesian method can reduce the systematic bias to a negligible level of ∼1% in the retrieved \(n_{\mathrm{m}}F_{2}\) and ∼1 km in the retrieved \(h_{\mathrm{m}}F_{2}\) . Our study provides a novel method for FUV remote sensing data analysis and an improved data set for ionospheric research.

The origin and evolution of Saturn’s rings is critical to understanding the Saturnian system as a whole. Here, we discuss the physical and chemical composition of the rings, as a foundation for evolutionary models described in subsequent chapters. We review the physical characteristics of the main rings, and summarize current constraints on their chemical composition. Radial trends are observed in temperature and to a limited extent in particle size distribution, with the C ring exhibiting higher temperatures and a larger population of small particles. The C ring also shows evidence for the greatest abundance of silicate material, perhaps indicative of formation from a rocky body. The C ring and Cassini Division have lower optical depths than the A and B rings, which contributes to the higher abundance of the exogenous neutral absorber in these regions. Overall, the main ring composition is strongly dominated by water ice, with minor silicate, UV absorber, and neutral absorber components. Sampling of the innermost D ring during Cassini’s Grand Finale provides a new set of in situ constraints on the ring composition, and we explore ongoing work to understand the linkages between the main rings and the D ring. The D ring material is organic- and silicate-rich and water-poor relative to the main rings, with a large population of small grains. This composition may be explained in part by volatile losses in the D ring, and current constraints suggest some degree of fractionation rather than sampling of the bulk D ring material.

Chondrules are iconic sub-millimeter spheroids representing the most abundant high-temperature dust formed during the evolution of the circumsolar disk. Chondrules have been the subject of a great deal of research, but no consensus has yet emerged as to their formation conditions. In particular, the question of whether chondrules are of nebular or planetary origin remains largely debated. Building upon decades of chondrule investigation and recent headways in combining petrographic observations and O−Ti−Cr isotopic compositions, we here propose a comprehensive vision of chondrule formation. This holistic approach points toward a nebular origin of both NC and CC chondrules, with repetitive high-temperature recycling processes controlling the petrographic and isotopic diversities shown by chondrules. Chondrule precursors correspond to mixing between (i) early-formed refractory inclusions ± NC-like dust and (ii) previous generation of chondrules ± CI-like material. Chondrule formation took place under open conditions with gas-melt interactions with multi-species gas (H2O, Mg, SiO) playing a key role for establishing their characteristics. Petrographic and isotopic systematics do not support disk-wide transport of chondrules but point toward local formation of chondrules within their respective accretion reservoirs. Altogether, this shows that several generations of genetically-related chondrules (i.e., deriving from each other) co-exist in chondrites. In addition to supporting the nebular brand of chondrule-forming scenarios, this argues for repetitive and extremely localized heating events for producing chondrules.

There is ample evidence for magnetic reconnection in the solar system, but it is a nontrivial task to visualize, to determine the proper approaches and frames to study, and in turn to elucidate the physical processes at work in reconnection regions from in-situ measurements of plasma particles and electromagnetic fields. Here an overview is given of a variety of single- and multi-spacecraft data analysis techniques that are key to revealing the context of in-situ observations of magnetic reconnection in space and for detecting and analyzing the diffusion regions where ions and/or electrons are demagnetized. We focus on recent advances in the era of the Magnetospheric Multiscale mission, which has made electron-scale, multi-point measurements of magnetic reconnection in and around Earth’s magnetosphere.

The JUpiter Icy Moon Explorer mission (JUICE) was designed to investigate Jupiter, its environment and its icy moons with at least one Europa flyby, a high inclination phase around Jupiter and a 280 days long near polar orbital phase around Ganymede, with 130 days on a low circular orbit. The goal of the JUICE mission analysis consisted in implementing these mission elements within a tight mass and radiation budget. A shift in the nominal launch date from June 2022 to September 2022 then April 2023 resulted in an arrival date at Jupiter in July 2031, close to equinox, so that the duration of eclipses by Jupiter became a major issue. A mission scheme meeting the requirements was designed using innovative approaches such as a double swing-by of the Moon and the Earth and a low energy endgame targeting a grazing Callisto flyby then grazing Ganymede encounters. Thanks to a near optimum launch date and launcher performance with full tanks, the post-launch Delta-V margins (150 m/s) made it possible to re-instate a 200 km circular orbital phase at the end of the nominal mission as planned in the mission proposal. The remaining Delta-V margin (55 m/s) and that expected from clean-up costs lower than allocated make it possible, while keeping adequate margins for contingencies, to consider significant improvements of the baseline mission scheme, in particular a higher maximum inclination during the tour and an inclination on the 200 km orbit close to Sun-synchronous, so that a long extended mission can be considered.

The sampling of extraterrestrial bodies is a critical technology in deep space exploration. Analyzing these samples allows researchers to uncover valuable information about the composition, structure, and evolutionary history of these celestial bodies. Compared to alternative sampling methods such as shoveling and grinding, drilling offers the advantage of obtaining larger sample volumes while preserving sample integrity. Furthermore, it enables sampling at various depths and terrains, making it an essential approach for acquiring samples from extraterrestrial environments. However, drill-based sampling devices are versatile, and their working principles and methods vary across different exploration missions and celestial bodies’ environments. This paper provides a comprehensive investigation into the progress made in drill-based sampling devices for extraterrestrial bodies. It begins by introducing the environmental and geological characteristics of the target celestial bodies, analyzing how these factors impact the structural design and operational parameters of sampling devices. The research then reviews drill-based sampling devices used in previous extraterrestrial exploration missions and examines the latest advancements in drill-based sampling technology. Based on different drilling depths, this study categorizes drill-based sampling devices into seven groups: small drills, pneumatic surface drills, single-rod drills, multi-rod drills, pneumatic deep probes, cable-based drills, and terrestrial ice penetration drills. It also provides an analysis of the operational characteristics, advantages and disadvantages of these seven types of drill-based sampling devices. The paper further outlines the technical difficulties and challenges encountered during the sampling of extraterrestrial bodies and concludes by presenting prospects for the future development of drill-based sampling technology for extraterrestrial bodies.

The lunar surface undergoes various space weathering and impact processes, which shape the regolith and expose boulders. Using high-resolution Lunar Reconnaissance Orbiter (LRO) Narrow Angle Camera imagery and associated Digital Elevation Models, we investigate regolith thicknesses and boulder densities at the four candidate landing sites of the Emirates Lunar Mission Rashid-1 rover: the floor-fractured crater Atlas and the Sinus Iridum, Oceanus Procellarum and Lacus Somniorum maria. The regolith thickness is estimated using the small crater morphology method, by mapping 3413 central mound, flat-bottomed, concentric craters (<350 m in diameter). Boulders were counted manually and compared with LRO Diviner rock abundance and mini-RF Circular Polarisation Ratio global maps. There is no obvious correlation between the site’s age, average regolith thickness and boulder density. The “Depth-Age hypothesis” is not confirmed here: Atlas (3.8 Gyr) has the thinnest regolith (median: 1.2 m), Procellarum (1.9 Gyr) and Somniorum (3.7 Gyr) have similar thicknesses (1.7 m and 1.8 m respectively), and the regolith in Iridum (3.4 Gyr) is the thickest (2.9 m). The estimated regolith thickness is highly variable laterally within the landing ellipses. Boulder fields in the landing areas are well-correlated with higher Diviner rock abundance values, and with locally thicker patches of regolith. The relatively thin regolith in Atlas could be related to its complex geology involving multiple volcanic episodes. Orbital estimates of regolith thickness and boulder distribution remain key for landing safety and trafficability assessments during mission preparations, and bring key insights into the local history of the regolith through crater morphologies.

Uranus distinguishes itself from other planets in the Solar System with a range of remarkable attributes, including a magnetosphere with a unique configuration, its quiescent atmosphere, its heating imbalance, its dense and narrow rings, and its unusually dark and tectonically processed icy satellites. Yet no mission to date has investigated either this ice giant or Neptune from up close. A Uranus Orbiter and Probe has thus been identified as the highest-priority new NASA Flagship mission for initiation in the decade 2023–2032. One invaluable instrument on a Uranus probe is a mass spectrometer experiment that analyzes the planet’s chemical composition in situ in real-time during the probe’s descent through the atmosphere. The selection of a mass spectrometer experiment is profoundly driven by the scientific questions the mission seeks to address and necessitates the accurate measurements of crucial elements including their isotope ratios. In addition to fulfilling the posed science requirements, the chosen experiment must adhere to stringent constraints such as mass, power, and size limitations while also prioritizing speed, simplicity of operation, a high level of reliability, and a completely autonomous operation. Here, we offer a succinct overview of the scientific rationale driving the Uranus probe mission, exploring various potential configurations for the mass spectrometer experiment, detailing instruments that complement a mass spectrometer, and discussing key factors that influence the mission’s profile. We also address the possibility of a collaborative effort between NASA and ESA, which could play a pivotal role in ensuring the successful development of this groundbreaking mission.

European Space Agency’s Mars Express (MEX) has been orbiting Mars for 20 years and its instruments have provided a plethora of observations of atmospheric dust and clouds. These observations have been analysed to produce many unique views of the processes leading to dust lifting and cloud formation, and a full picture of the climatologies of dust and clouds has emerged. Moreover, the orbit of MEX enables viewing the planet at many local times, giving a unique access to the diurnal variations of the atmosphere. This article provides an overview of the observations of dust and clouds on Mars by MEX, complemented by the Trace Gas Orbiter that has been accompanying MEX on orbit for some years.

As a first step in preparing for the return of samples from the Moon by the Artemis Program, NASA initiated the Apollo Next Generation Sample Analysis Program (ANGSA). ANGSA was designed to function as a low-cost sample return mission and involved the curation and analysis of samples previously returned by the Apollo 17 mission that remained unopened or stored under unique conditions for 50 years. These samples include the lower portion of a double drive tube previously sealed on the lunar surface, the upper portion of that drive tube that had remained unopened, and a variety of Apollo 17 samples that had remained stored at −27 °C for approximately 50 years. ANGSA constitutes the first preliminary examination phase of a lunar “sample return mission” in over 50 years. It also mimics that same phase of an Artemis surface exploration mission, its design included placing samples within the context of local and regional geology through new orbital observations collected since Apollo and additional new “boots-on-the-ground” observations, data synthesis, and interpretations provided by Apollo 17 astronaut Harrison Schmitt. ANGSA used new curation techniques to prepare, document, and allocate these new lunar samples, developed new tools to open and extract gases from their containers, and applied new analytical instrumentation previously unavailable during the Apollo Program to reveal new information about these samples. Most of the 90 scientists, engineers, and curators involved in this mission were not alive during the Apollo Program, and it had been 30 years since the last Apollo core sample was processed in the Apollo curation facility at NASA JSC. There are many firsts associated with ANGSA that have direct relevance to Artemis. ANGSA is the first to open a core sample previously sealed on the surface of the Moon, the first to extract and analyze lunar gases collected in situ, the first to examine a core that penetrated a lunar landslide deposit, and the first to process pristine Apollo samples in a glovebox at −20 °C. All the ANGSA activities have helped to prepare the Artemis generation for what is to come. The timing of this program, the composition of the team, and the preservation of unopened Apollo samples facilitated this generational handoff from Apollo to Artemis that sets up Artemis and the lunar sample science community for additional successes.

Theoretical studies of giant planet formation suggest that substantial quantities of metals—elements heavier than hydrogen and helium—can be delivered by solid accretion during the envelope-assembly phase. This process of metal enhancement of the envelope is believed to diminish as a function of planet mass, leading to predictions for a mass-metallicity relationship. Supporting evidence for this picture is provided by the abundance of CH4 in solar system giant planets, where CH4 abundance, unlike H2O, is unaffected by condensate cloud formation. However, all of the solar system giants exhibit some evidence for stratification of metals outside of their cores. In this context, two fundamental questions are whether metallicity of giant planets inferred from observations of the outer envelope layers represents the bulk metallicity of these planets, and if not, how are metals distributed within giant planets. Comparing the mass-metallicity relationship for solar system giant planets, inferred from the observed CH4 abundance, with various tracers of metallicity in the exoplanet population, has yielded a range of results. There is evidence of a solar-system-like mass-metallicity trend using bulk density estimates of exoplanet metallicity. However, transit-spectroscopy-based tracers of exoplanet metallicity, which probe only the outer layers of the envelope, are less clear about a mass-metallicity trend and raise the question of whether radial composition gradients exist in some giant exoplanets. The large number of known exoplanets enables statistical characterization of planet properties. We develop a formalism for comparing both the metallicity inferred for the outer envelope and the metallicity inferred using the bulk density and show this combination may offer insights into the broader question of metal stratification within planetary envelopes. Our analysis suggests that future exoplanet observations with JWST and Ariel will be able to shed light on the conditions governing radial composition gradients in exoplanets and, perhaps, provide information about the factors controlling stratification and convection in our solar system gas giants.

The Rashid-1 rover, being the main component of the Emirates Lunar Mission (ELM) developed by the Mohammed Bin Rashid Space Center (MBRSC), was launched in late 2022 on-board the Hakuto lunar lander. The scientific objectives of the rover were to investigate the regolith formations of our natural satellite and analyze the geology of its landing area. To perform its investigations, Rashid-1 carried two wide-angle cameras (CAM-1 and CAM-2) and a narrow-angle microscope camera (CAM-M) equipped with Bayer color filter arrays. The mission was however unsuccessful due to a lander failure during lunar descent which caused the loss of the payload. Despite this drawback, significant insights into exploration rover imaging have been gained through the extensive work done prior to launch to achieve the highest image quality from the on-board cameras, and the resulting CASPIP software package will be used for upcoming rover missions. This paper presents the CAM-1 and CAM-2 instruments and the planned advanced image products. In the first part, we provide a detailed presentation of the calibration of the instruments including their optical parameters, characterization of the detector in term of flat-field, optical ghosts, dark current, spectral sensitivities and distortion. The second part of the paper deals with colorimetry, focusing on the colorimetric characterization of the instrument as well as a description of the correction applied to obtain images expressed in the standard color space CIE XYZ and displayed properly in sRGB. Finally, the third part describes advanced image products developed to assist experts (geologists, navigation engineers). It includes a tool for distance visualization directly inside an image, and the creation of 3D images through stereoscopic reconstruction.

We present the state of the art on the study of surfaces and tenuous atmospheres of the icy Galilean satellites Ganymede, Europa and Callisto, from past and ongoing space exploration conducted with several spacecraft to recent telescopic observations, and we show how the ESA JUICE mission plans to explore these surfaces and atmospheres in detail with its scientific payload. The surface geology of the moons is the main evidence of their evolution and reflects the internal heating provided by tidal interactions. Surface composition is the result of endogenous and exogenous processes, with the former providing valuable information about the potential composition of shallow subsurface liquid pockets, possibly connected to deeper oceans. Finally, the icy Galilean moons have tenuous atmospheres that arise from charged particle sputtering affecting their surfaces. In the case of Europa, plumes of water vapour have also been reported, whose phenomenology at present is poorly understood and requires future close exploration. In the three main sections of the article, we discuss these topics, highlighting the key scientific objectives and investigations to be achieved by JUICE. Based on a recent predicted trajectory, we also show potential coverage maps and other examples of reference measurements. The scientific discussion and observation planning presented here are the outcome of the JUICE Working Group 2 (WG2): “Surfaces and Near-surface Exospheres of the Satellites, dust and rings”.

Dark matter structures within strong gravitational lens galaxies and along their lines of sight leave a gravitational imprint on the multiple images of lensed sources. Strong gravitational lensing provides, therefore, a key test of different dark matter models. In this article, we describe how galaxy-scale strong gravitational lensing observations are sensitive to the physical nature of dark matter. We provide an historical perspective of the field, and review its current status. We discuss the challenges and advances in terms of data, treatment of systematic errors and theoretical predictions, that will enable one to deliver a stringent and robust test of different dark matter models in the next decade. With the advent of the next generation of sky surveys, the number of known strong gravitational lens systems is expected to increase by several orders of magnitude. Coupled with high-resolution follow-up observations, these data will provide a key opportunity to constrain the properties of dark matter with strong gravitational lensing.

Microlensing near macro-caustics is a complex phenomenon in which swarms of micro-images produced by micro-caustics form on both sides of a macro-critical curve. Recent discoveries of highly magnified images of individual stars in massive galaxy cluster lenses, predicted to be formed by these micro-image swarms, have stimulated studies on this topic. In this article, we explore microlensing near macro-caustics using both simulations and analytic calculations. We show that the mean total magnification of the micro-image swarms follows that of an extended source in the absence of microlensing. Micro-caustics join into a connected network in a region around the macro-critical line of a width proportional to the surface density of microlenses; within this region, the increase of the mean magnification toward the macro-caustic is driven by the increase of the number of micro-images rather than individual magnifications of micro-images. The maximum achievable magnification in micro-caustic crossings decreases with the mass fraction in microlenses. We conclude with a review of applications of this microlensing phenomenon, including limits to the fraction of dark matter in compact objects, and searches of Population III stars and dark matter subhalos. We argue that the discovered highly magnified stars at cosmological distances already imply that less than ∼ 10% of the dark matter may be in the form of compact objects with mass above \(\sim 10^{-6}~M_{\odot }\) .

Noble gases are accreted to the giant planets as part of the gas component of the planet-forming disk. While heavier noble gases can separate from the evolution of the hydrogen-rich gas, helium is thought to remain at the protosolar H/He ratio \(Y_{\mathrm{proto}}\sim 0.27\) –0.28. However, spacecraft observations revealed a depletion in helium in the atmospheres of Jupiter, Saturn, and Uranus. For the gas giants, this is commonly seen as indication of H/He phase separation at greater depths. Here, we apply predictions of the H/He phase diagram and three H/He-EOS to compute the atmospheric helium mass abundance \(Y_{\mathrm{atm}}\) as a result of H/He phase separation. We obtain a strong depletion \(Y_{\mathrm{atm}}<0.1\) for the ice giants if they are adiabatic. Introducing a thermal boundary layer at the Z-poor/Z-rich compositional transition with a temperature increase of up to a few 1000 K, we obtain a weak depletion in Uranus as observed. Our results suggest dissimilar internal structures between Uranus and Neptune. An accurate in-situ determination of their atmospheric He/H ratio would help to constrain their internal structures. This is even more true for Saturn, where we find that any considered H/He phase diagram and H/He-EOS would be consistent with any observed value. However, some H/He-EOS and phase diagram combinations applied to both Jupiter and Saturn require an outer stably-stratified layer at least in one of them.

Saturn’s mid-sized icy moons have complex relationships with Saturn’s interior, the rings, and with each other, which can be expressed in their shapes, interiors, and geology. Observations of their physical states can, thus, provide important constraints on the ages and formation mechanism(s) of the moons, which in turn informs our understanding of the formation and evolution of Saturn and its rings. Here, we describe the cratering records of the mid-sized moons and the value and limitations of their use for constraining the histories of the moons. We also discuss observational constraints on the interior structures of the moons and geologically-derived inferences on their thermal budgets through time. Overall, the geologic records of the moons (with the exception of Mimas) include evidence of epochs of high heat flows, short- and long-lived subsurface oceans, extensional tectonics, and considerable cratering. Curiously, Mimas presents no clear evidence of an ocean within its surface geology, but its rotation and orbit indicate a present-day ocean. While the moons need not be primordial to produce the observed levels of interior evolution and geologic activity, there is likely a minimum age associated with their development that has yet to be determined. Uncertainties in the populations impacting the moons makes it challenging to further constrain their formation timeframes using craters, whereas the characteristics of their cores and other geologic inferences of their thermal evolutions may help narrow down their potential histories. Disruptive collisions may have also played an important role in the formation and evolution of Saturn’s mid-sized moons, and even the rings of Saturn, although more sophisticated modeling is needed to determine the collision conditions that produce rings and moons that fit the observational constraints. Overall, the existence and physical characteristics of Saturn’s mid-sized moons provide critical benchmarks for the development of formation theories.

The JUpiter ICy moons Explorer (JUICE) of ESA was launched on 14 April 2023 and will arrive at Jupiter and its moons in July 2031. In this review article, we describe how JUICE will investigate the interior of the three icy Galilean moons, Ganymede, Callisto and Europa, during its Jupiter orbital tour and the final orbital phase around Ganymede. Detailed geophysical observations about the interior of the moons can only be performed from close distances to the moons, and best estimates of signatures of the interior, such as an induced magnetic field, tides and rotation variations, and radar reflections, will be obtained during flybys of the moons with altitudes of about 1000 km or less and during the Ganymede orbital phase at an average altitude of 490 km. The 9-month long orbital phase around Ganymede, the first of its kind around another moon than our Moon, will allow an unprecedented and detailed insight into the moon’s interior, from the central regions where a magnetic field is generated to the internal ocean and outer ice shell. Multiple flybys of Callisto will clarify the differences in evolution compared to Ganymede and will provide key constraints on the origin and evolution of the Jupiter system. JUICE will visit Europa only during two close flybys and the geophysical investigations will focus on selected areas of the ice shell. A prime goal of JUICE is the characterisation of the ice shell and ocean of the Galilean moons, and we here specifically emphasise the synergistic aspects of the different geophysical investigations, showing how different instruments will work together to probe the hydrosphere. We also describe how synergies between JUICE instruments will contribute to the assessment of the deep interior of the moons, their internal differentiation, dynamics and evolution. In situ measurements and remote sensing observations will support the geophysical instruments to achieve these goals, but will also, together with subsurface radar sounding, provide information about tectonics, potential plumes, and the composition of the surface, which will help understanding the composition of the interior, the structure of the ice shell, and exchange processes between ocean, ice and surface. Accurate tracking of the JUICE spacecraft all along the mission will strongly improve our knowledge of the changing orbital motions of the moons and will provide additional insight into the dissipative processes in the Jupiter system. Finally, we present an overview of how the geophysical investigations will be performed and describe the operational synergies and challenges.