Olivier Witasse

Electromagnetic induction is a method to probe interiors of planetary bodies and icy moons. In particular, the magnetic field generated by the flow of the subsurface ocean (OIMF) has attracted attention in the context of the Europa Clipper and Juice satellite missions. Recent studies suggest that extracting the OIMF signal from the satellite measurements is feasible on Ganymede, more uncertain on Europa. We therefore investigate the usage of the OIMF to constrain the ocean flow structure. In the absence of real data, we performed a series of synthetic experiments, focusing separately on Ganymede and Europa. Our results show that the vertical structure of the toroidal flow cannot be constrained from the OIMF on Ganymede, even in an idealised test case. However, the vertically integrated toroidal flow can be obtained from the OIMF even if the OIMF at the lowest spherical-harmonic degrees, where Ganymede's core field dominates, is not used. General characteristics of the poloidal flow, such as the number of convection cells and their size, can also be recovered from the OIMF. However, this is only possible under certain a priori assumptions about the poloidal flow. On Europa, the vertical structure of the toroidal flow can be reconstructed but only in the upper parts of the ocean. The reconstruction of the poloidal flow is similar to that on Ganymede. The different inverse-problem sensitivity can be attributed to the different periods of the OIMF signals. The OIMF is stationary on Ganymede and periodic with the synodic period on Europa.

The most intense radio feature in the Solar System are the solar Type‐III radio bursts, which are associated with electron beams that propagate along open magnetic field lines. Although solar radio bursts have been studied since the 1940s, observations remain mainly restricted within 1 AU. In this study, we explore 16.5 years of data (2005–2021) from the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) onboard Mars Express. While not the central aim of the instrument, MARSIS has been recording solar radio bursts since its deployment in mid‐2005. Given the potential of this new radio burst data set for heliophysics studies, we have created a catalog of Type‐III solar radio burst events between 1.38 and 1.66 AU (Mars' orbit) within the frequency range of 0.1 and 5.5 MHz and with an instrument measuring cadence of 7.5 s. We demonstrate that these emissions seen at Mars come from the Sun, follow the solar cycle pattern, and are not influenced by the planet's own properties such as crustal magnetic fields. We also compare the propagation of a few illustrative events from the Sun to Mars to demonstrate the utility of this new data set for heliophysics studies. Mars catalogs provide a fundamentally new perspective on the spatial extent, directivity, and evolution of solar radio emission in the inner heliosphere. It serves as an essential benchmark for multi‐point heliospheric studies and for constraining radio emissions mechanisms beyond Earth orbit, and demonstrating the usefulness of planetary missions in contributing to heliophysics science in diverse ways.

The European Space Agency’s JUpiter ICy moons Explorer (JUICE), launched in April 2023, aims to assess the potential habitability of Jupiter’s icy moons–Ganymede, Europa, and Callisto–while investigating the Jovian system as a whole. During its cruise phase, JUICE performed in August 2024 the first-ever combined Moon–Earth gravity assist (LEGA), a critical milestone for optimizing its trajectory toward Jupiter. Beyond its navigation objectives, this unique event provided an exceptional opportunity for in-flight calibration and validation of the scientific payload under known Earth environment. Despite significant operational constraints, all instruments were operated. The Moon flyby enabled precise calibration of remote sensing instruments, radar testing and in situ measurements of the Moon’s environment while within the Earth’s magnetotail, as well as the detection of a spacecraft outgassing event observed by multiple instruments and sensors. The subsequent Earth flyby complemented these efforts through atmospheric, magnetospheric, and radiation belt observations. These measurements confirmed the excellent performances of the JUICE instruments and demonstrated the mission’s capability to deliver high-quality scientific data already during cruise. This campaign represents a key step in preparing for nominal operations at Jupiter while providing valuable scientific results.

The European Space Agency’s JUpiter ICy moons Explorer (JUICE), launched in April 2023, aims to assess the potential habitability of Jupiter’s icy moons–Ganymede, Europa, and Callisto–while investigating the Jovian system as a whole. During its cruise phase, JUICE performed in August 2024 the first-ever combined Moon–Earth gravity assist (LEGA), a critical milestone for optimizing its trajectory toward Jupiter. Beyond its navigation objectives, this unique event provided an exceptional opportunity for in-flight calibration and validation of the scientific payload under known Earth environment. Despite significant operational constraints, all instruments were operated. The Moon flyby enabled precise calibration of remote sensing instruments, radar testing and in situ measurements of the Moon’s environment while within the Earth’s magnetotail, as well as the detection of a spacecraft outgassing event observed by multiple instruments and sensors. The subsequent Earth flyby complemented these efforts through atmospheric, magnetospheric, and radiation belt observations. These measurements confirmed the excellent performances of the JUICE instruments and demonstrated the mission’s capability to deliver high-quality scientific data already during cruise. This campaign represents a key step in preparing for nominal operations at Jupiter while providing valuable scientific results.

The European Space Agency’s JUpiter ICy moons Explorer (JUICE), launched in April 2023, aims to assess the potential habitability of Jupiter’s icy moons–Ganymede, Europa, and Callisto–while investigating the Jovian system as a whole. During its cruise phase, JUICE performed in August 2024 the first-ever combined Moon–Earth gravity assist (LEGA), a critical milestone for optimizing its trajectory toward Jupiter. Beyond its navigation objectives, this unique event provided an exceptional opportunity for in-flight calibration and validation of the scientific payload under known Earth environment. Despite significant operational constraints, all instruments were operated. The Moon flyby enabled precise calibration of remote sensing instruments, radar testing and in situ measurements of the Moon’s environment while within the Earth’s magnetotail, as well as the detection of a spacecraft outgassing event observed by multiple instruments and sensors. The subsequent Earth flyby complemented these efforts through atmospheric, magnetospheric, and radiation belt observations. These measurements confirmed the excellent performances of the JUICE instruments and demonstrated the mission’s capability to deliver high-quality scientific data already during cruise. This campaign represents a key step in preparing for nominal operations at Jupiter while providing valuable scientific results.

The European Space Agency’s JUpiter ICy moons Explorer (JUICE), launched in April 2023, aims to assess the potential habitability of Jupiter’s icy moons–Ganymede, Europa, and Callisto–while investigating the Jovian system as a whole. During its cruise phase, JUICE performed in August 2024 the first-ever combined Moon–Earth gravity assist (LEGA), a critical milestone for optimizing its trajectory toward Jupiter. Beyond its navigation objectives, this unique event provided an exceptional opportunity for in-flight calibration and validation of the scientific payload under known Earth environment. Despite significant operational constraints, all instruments were operated. The Moon flyby enabled precise calibration of remote sensing instruments, radar testing and in situ measurements of the Moon’s environment while within the Earth’s magnetotail, as well as the detection of a spacecraft outgassing event observed by multiple instruments and sensors. The subsequent Earth flyby complemented these efforts through atmospheric, magnetospheric, and radiation belt observations. These measurements confirmed the excellent performances of the JUICE instruments and demonstrated the mission’s capability to deliver high-quality scientific data already during cruise. This campaign represents a key step in preparing for nominal operations at Jupiter while providing valuable scientific results.

The European Space Agency’s JUpiter ICy moons Explorer (JUICE), launched in April 2023, aims to assess the potential habitability of Jupiter’s icy moons–Ganymede, Europa, and Callisto–while investigating the Jovian system as a whole. During its cruise phase, JUICE performed in August 2024 the first-ever combined Moon–Earth gravity assist (LEGA), a critical milestone for optimizing its trajectory toward Jupiter. Beyond its navigation objectives, this unique event provided an exceptional opportunity for in-flight calibration and validation of the scientific payload under known Earth environment. Despite significant operational constraints, all instruments were operated. The Moon flyby enabled precise calibration of remote sensing instruments, radar testing and in situ measurements of the Moon’s environment while within the Earth’s magnetotail, as well as the detection of a spacecraft outgassing event observed by multiple instruments and sensors. The subsequent Earth flyby complemented these efforts through atmospheric, magnetospheric, and radiation belt observations. These measurements confirmed the excellent performances of the JUICE instruments and demonstrated the mission’s capability to deliver high-quality scientific data already during cruise. This campaign represents a key step in preparing for nominal operations at Jupiter while providing valuable scientific results.

Radio occultation (RO) is a very powerful technique as it offers great opportunities to study planetary atmospheres, providing information about their ionosphere and neutral atmosphere. Standard methods use a radio link at S and/or X bands between a spacecraft orbiting a planet and a ground station on the Earth. At Mars, such measurements have been conducted since the 60s. Three most recent data sets are from Mars Global Surveyor, Mars Express and the Mars Atmosphere and Volatile Evolution satellites. Furthermore, the possibility to obtain information about the Martian atmosphere with mutual RO events, using data from NASA Mars Odyssey and Mars Reconnaissance Orbiters, has been demonstrated by NASA scientists in 2015. Taking advantage of two European spacecraft in orbit around Mars, the ESA is currently performing an experiment that consists of mutual radio occultations between Mars Express (MEX) and ExoMars Trace Gas Orbiter (TGO). In preparation for MEX and TGO data inversion and analysis, a simulation‐based strategy has been adopted and an algorithm, including the associated software, able to retrieve vertical electron density profiles from Doppler shift measurements has been implemented and validated. Subsequently, to test the mentioned algorithm with experimental data, the same three mutual RO events considered by NASA scientists have been re‐processed. In this work, the research activities carried out through the simulation studies and the results obtained by the application of the mentioned inversion algorithm to experimental data are presented.

The European Space Agency’s JUpiter ICy moons Explorer (JUICE), launched in April 2023, aims to assess the potential habitability of Jupiter’s icy moons–Ganymede, Europa, and Callisto–while investigating the Jovian system as a whole. During its cruise phase, JUICE performed in August 2024 the first-ever combined Moon–Earth gravity assist (LEGA), a critical milestone for optimizing its trajectory toward Jupiter. Beyond its navigation objectives, this unique event provided an exceptional opportunity for in-flight calibration and validation of the scientific payload under known Earth environment. Despite significant operational constraints, all instruments were operated. The Moon flyby enabled precise calibration of remote sensing instruments, radar testing and in situ measurements of the Moon’s environment while within the Earth’s magnetotail, as well as the detection of a spacecraft outgassing event observed by multiple instruments and sensors. The subsequent Earth flyby complemented these efforts through atmospheric, magnetospheric, and radiation belt observations. These measurements confirmed the excellent performances of the JUICE instruments and demonstrated the mission’s capability to deliver high-quality scientific data already during cruise. This campaign represents a key step in preparing for nominal operations at Jupiter while providing valuable scientific results.