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Magnetometers are essential for scientific investigation of planetary bodies and are therefore ubiquitous on missions in space. Fluxgate and optically pumped atomic gas based magnetometers are typically flown because of their proven performance, reliability, and ability to adhere to the strict requirements associated with space missions. However, their complexity, size, and cost prevent their applicability in smaller missions involving cubesats. Conventional solid-state based magnetometers pose a viable solution, though many are prone to radiation damage and plagued with temperature instabilities. In this work, we report on the development of a new self-calibrating, solid-state based magnetometer which measures magnetic field induced changes in current within a SiC pn junction caused by the interaction of external magnetic fields with the atomic scale defects intrinsic to the semiconductor. Unlike heritage designs, the magnetometer does not require inductive sensing elements, high frequency radio, and/or optical circuitry and can be made significantly more compact and lightweight, thus enabling missions leveraging swarms of cubesats capable of science returns not possible with a single large-scale satellite. Additionally, the robustness of the SiC semiconductor allows for operation in extreme conditions such as the hot Venusian surface and the high radiation environment of the Jovian system.

Electrically detected magnetic resonance (EDMR) is a promising method to readout spins in miniaturized devices utilized as quantum magnetometers. However, the sensitivity has remained challenging. In this study, we present a tandem (de-)modulation technique based on a combination of magnetic field and radio frequency modulation. By enabling higher demodulation frequencies to avoid 1/f-noise, enhancing self-calibration capabilities, and eliminating background signals by 3 orders of magnitude, this technique represents a significant advancement in the field of EDMR-based sensors. This novel approach paves the way for EDMR being the ideal candidate for ultra-sensitive magnetometry at ambient conditions without any optical components, which brings it one step closer to a chip-based quantum sensor for future applications.

Several bodies in the outer solar system are believed to host liquid water oceans underneath their icy surfaces. Knowledge of the hydrosphere properties is essential for understanding and assessing their habitability. We introduce a methodology based on Bayesian inference that enables a robust characterization of the hydrosphere through the combination of gravity and magnetic induction data. The interior models retrieved are consistent with the geophysical observations, leading to probability distributions for the relevant interior properties. We apply this joint inversion approach to constrain Europa's hydrosphere with gravity and magnetic field measurements acquired by the Galileo mission. Our results indicate that the combination of these datasets allows simultaneous constraints on the ice shell and ocean thickness, enhancing our knowledge of the hydrosphere structure. This methodology is valuable for synergistic interior science investigations of several missions in development or in planning, including Europa Clipper, JUICE and the Uranus Orbiter and Probe. Plain Language Summary The outer solar system has several moons with icy surfaces that may hide oceans of liquid water beneath them. Studying these oceans is important for assessing whether these worlds can harbor life. We have developed a novel technique to study these potentially habitable oceans by combining measurements of the gravity and magnetic fields of these icy moons. We use a statistical method to generate models of the moon's interior that are consistent with the available gravity and magnetic field measurements. By applying this method to measurements of Jupiter's moon, Europa, we show that it can provide robust estimates of the thicknesses of the moon's ice shell and the subsurface ocean. This new technique will be useful for studying the interior of Europa and other icy moons with the data acquired by future missions, such as Europa Clipper, JUICE, and the Uranus Orbiter and Probe. Key Points We developed a technique to combine measurements of gravity and magnetic field that improves the characterization of icy moon hydrospheres We applied this joint inversion to constrain Europa's ice and ocean thicknesses with gravity and magnetic induction data from Galileo Our results demonstrate that the joint inversion of these observations allows us to better understand the hydrosphere's structure

The objective of the Psyche Magnetometry Investigation is to test the hypothesis that asteroid (16) Psyche formed from the core of a differentiated planetesimal. To address this, the Psyche Magnetometer will measure the magnetic field around the asteroid to search for evidence of remanent magnetization. Paleomagnetic measurements of meteorites and dynamo theory indicate that a diversity of planetesimals once generated dynamo magnetic fields in their metallic cores. Likewise, the detection of a strong magnetic moment ( > 2 × 10 14 Am 2 ) at Psyche would likely indicate that the body once generated a core dynamo, implying that it formed by igneous differentiation. The Psyche Magnetometer consists of two three-axis fluxgate Sensor Units (SUs) mounted 0.7 m apart along a 2.15-m long boom and connected to two Electronics Units (EUs) located within the spacecraft bus. The Magnetometer samples at up to 50 Hz, has a range of ± 80 , 000 nT , and an instrument noise of 39 pT axis − 1 3 σ integrated over 0.1 to 1 Hz. The two pairs of SUs and EUs provide redundancy and enable gradiometry measurements to suppress noise from flight system magnetic fields. The Magnetometer will be powered on soon after launch and acquire data for the full duration of the mission. The ground data system processes the Magnetometer measurements to obtain an estimate of Psyche’s dipole moment.

The magnetometer investigation of the Galileo mission used the phenomenon of magnetic induction to produce the most compelling evidence that subsurface oceans exist within our solar system. Although there is high certainty that the induced field measured at Europa is attributed to a global‐scale subsurface ocean, there is still uncertainty around the possibility that the induced field measured at Callisto is evidence of an ocean. This uncertainty is due to the presence of a conductive ionosphere, which will also produce an induction signal in response to Jupiter's strong time‐varying magnetic field. Therefore, it is not yet known whether the observed induced field is attributable to the ionosphere, an ocean, or a combination of both. In this work, we use previously published simulations of Callisto's plasma interaction in combination with both an inverse and an ensemble forward modeling method to highlight the plausible range of interior properties of Callisto. We further constrain the ocean thickness and conductivity, ice shell thickness, and ionospheric conductivity that are required to explain the Galileo magnetometer observations. This is the first study to jointly consider all flybys to constrain the driving field and three flybys (C03, C09, and C10) to assess the induction response. Our results suggest that Callisto's response more likely arises from the combination of a thick conductive ocean and an ionosphere rather than from an ionosphere alone. Plain Language Summary Magnetic measurements can tell us about the properties of subsurface oceans in moons, because oscillating magnetic fields from the planet interact with the electrically conductive ocean. Measuring the magnetic field near the moon can tell us about the ocean's properties, such as how deep it is and how much dissolved salt is present. Studies of magnetic measurements near Callisto, a large icy moon of Jupiter, have so far been ambiguous, because Callisto has a substantial ionosphere that may mimic the magnetic response of an ocean. However, past studies examining this problem considered only a subset of the available data. We expand the analysis to include data from a broader set of flybys from the Galileo mission, and when we include all of the available close flybys, we find that a deep ocean inside Callisto provides the most compelling explanation of the magnetic measurements. Key Points We applied a multifrequency magnetic induction method to Galileo magnetometer observations at Callisto Joint assessment of flybys C03, C09, and C10 suggests that an ocean, and not an ionosphere alone, is required to explain the observations If an ocean is present, it is likely thick and deep

The Galileo mission to Jupiter revealed that Europa is an ocean world. The Galileo magnetometer experiment in particular provided strong evidence for a salty subsurface ocean beneath the ice shell, likely in contact with the rocky core. Within the ice shell and ocean, a number of tectonic and geodynamic processes may operate today or have operated at some point in the past, including solid ice convection, diapirism, subsumption, and interstitial lake formation. The science objectives of the Europa Clipper mission include the characterization of Europa’s interior; confirmation of the presence of a subsurface ocean; identification of constraints on the depth to this ocean, and on its salinity and thickness; and determination of processes of material exchange between the surface, ice shell, and ocean. Three broad categories of investigation are planned to interrogate different aspects of the subsurface structure and properties of the ice shell and ocean: magnetic induction, subsurface radar sounding, and tidal deformation. These investigations are supplemented by several auxiliary measurements. Alone, each of these investigations will reveal unique information. Together, the synergy between these investigations will expose the secrets of the Europan interior in unprecedented detail, an essential step in evaluating the habitability of this ocean world.

The goal of NASA’s Europa Clipper mission is to assess the habitability of Jupiter’s moon Europa. After entering Jupiter orbit in 2030, the flight system will collect science data while flying past Europa 49 times at typical closest approach distances of 25–100 km. The mission’s objectives are to investigate Europa’s interior (ice shell and ocean), composition, and geology; the mission will also search for and characterize any current activity including possible plumes. The science objectives will be accomplished with a payload consisting of remote sensing and in-situ instruments. Remote sensing investigations cover the ultraviolet, visible, near infrared, and thermal infrared wavelength ranges of the electromagnetic spectrum, as well as an ice-penetrating radar. In-situ investigations measure the magnetic field, dust grains, neutral gas, and plasma surrounding Europa. Gravity science will be achieved using the telecommunication system, and a radiation monitoring engineering subsystem will provide complementary science data. The flight system is designed to enable all science instruments to operate and gather data simultaneously. Mission planning and operations are guided by scientific requirements and observation strategies, while appropriate updates to the plan will be made tactically as the instruments and Europa are characterized and discoveries emerge. Following collection and validation, all science data will be archived in NASA’s Planetary Data System. Communication, data sharing, and publication policies promote visibility, collaboration, and mutual interdependence across the full Europa Clipper science team, to best achieve the interdisciplinary science necessary to understand Europa.

The goal of NASA’s Europa Clipper Mission is to investigate the habitability of the subsurface ocean within the Jovian moon Europa using a suite of ten investigations. The Europa Clipper Magnetometer (ECM) and Plasma Instrument for Magnetic Sounding (PIMS) investigations will be used in unison to characterize the thickness and electrical conductivity of Europa’s subsurface ocean and the thickness of the ice shell by sensing the induced magnetic field, driven by the strong time-varying magnetic field of the Jovian environment. However, these measurements will be obscured by the magnetic field originating from the Europa Clipper spacecraft. In this work, a magnetic field model of the Europa Clipper spacecraft is presented, characterized with over 260 individual magnetic sources comprising various ferromagnetic and soft-magnetic materials, compensation magnets, solenoids, and dynamic electrical currents flowing within the spacecraft. This model is used to evaluate the magnetic field at arbitrary points around the spacecraft, notably at the locations of the three fluxgate magnetometer sensors and four Faraday cups which make up ECM and PIMS, respectively. The model is also used to evaluate the magnetic field uncertainty at these locations via a Monte Carlo approach. Furthermore, both linear and non-linear gradiometry fitting methods are presented to demonstrate the ability to reliably disentangle the spacecraft field from the ambient using an array of three fluxgate magnetometer sensors mounted along an 8.5-meter (m) long boom. The method is also shown to be useful for optimizing the locations of the magnetometer sensors along the boom. Finally, we illustrate how the model can be used to visualize the magnetic field lines of the spacecraft, thus providing very insightful information for each investigation.

Global-scale properties of Europa’s putative ocean, including its depth, thickness, and conductivity, can be established from measurements of the magnetic field on multiple close flybys of the moon at different phases of the synodic and orbital periods such as those planned for the Europa Clipper mission. The Europa Clipper Magnetometer (ECM) has been designed and constructed to provide the required high precision, temporally stable measurements over the range of temperatures and other environmental conditions that will be encountered in the solar wind and at Jupiter. Three low-noise, tri-axial fluxgate sensors provided by the University of California, Los Angeles are controlled by an electronics unit developed at NASA’s Jet Propulsion Laboratory. Each fluxgate sensor measures the vector magnetic field over a wide dynamic range (±4000 nT per axis) with a resolution of 8 pT. A rigorous magnetic cleanliness program has been adopted for the spacecraft and its payload. The sensors are mounted far out on an 8.5 m boom to form a configuration that makes it possible to measure the remaining spacecraft field and remove its contribution to data from the outboard sensor. This paper provides details of the magnetometer design, implementation and testing, the ground calibrations and planned calibrations in cruise and in orbit at Jupiter, and the methods to be used to extract Europa’s inductive response from the data. Data will be collected at nominal rates of 1 or 16 samples/s and will be processed at UCLA and delivered to the Planetary Data System in a timely manner.

The Voyager 2 flyby of Uranus in 1986 revealed an unusually oblique and off-centred magnetic field. This single in situ measurement has been the basis of our interpretation of Uranus’s magnetosphere as the canonical extreme magnetosphere of the solar system; with inexplicably intense electron radiation belts and a severely plasma-depleted magnetosphere. However, the role of external forcing by the solar wind has rarely been considered in explaining these observations. Here we revisit the Voyager 2 dataset to show that Voyager 2 observed Uranus’s magnetosphere in an anomalous, compressed state that we estimate to be present less than 5% of the time. If the spacecraft had arrived only a few days earlier, the upstream solar wind dynamic pressure would have been ~20 times lower, resulting in a dramatically different magnetospheric configuration. We postulate that such a compression of the magnetosphere could increase energetic electron fluxes within the radiation belts and empty the magnetosphere of its plasma temporarily. Therefore, the interpretation of Uranus’s magnetosphere as being extreme may simply be a product of a flyby that occurred under extreme upstream solar wind conditions. A reanalysis of the Voyager 2 flyby of Uranus shows that it occurred during an extreme compression of the planet’s magnetosphere by the upstream solar wind. This would have had significant effects on the measurements made during the flyby.