The Europa Clipper Magnetometer

Abstract

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.

Electrical Conductivity of Subsurface Ocean Analogue Solutions from Molecular Dynamics Simulations

“…In the context of the planned magnetic investigations of Europa, we assess the needed precision of electrical conductivity data equivalent to the anticipated measurement uncertainty of the induction response. Assuming a measurement sensitivity consistent with that expected for the ECM 11 of ΔB = 1.5 nT, we compute the noise-equivalent increment of conductivity for Europa using the available frameworks PlanetProfile 37,38 and MoonMag. 39 This quantity establishes Assuming an uncertainty of retrieval of 1.5 nT in the induced magnetic field vector components (ΔB), the conductivity of hypothesized ocean fluids must be predicted to an uncertainty Δσ B at or below the line shown, or it will be a dominant source of uncertainty, greater than that of Europa Clipper's magnetic induction investigation.…”

“…The Europa Clipper Magnetometer (ECM) will sample the magnetic field near Europa with good coverage of Europa's orbital mean anomaly and Jupiter's magnetic phase (system III longitude), enabling retrieval of the induction response (phase and amplitude) for both the 11.2 h synodic period and for the longer (85.2 h) orbital-period oscillation. 11 To maximize the science return from this magnetic field investigation, the electrical conductivity of the relevant aqueous solutions must be precisely constrained. The electrical conductivity data set used by Hand and Chyba 4 consisted of measurements of candidate ocean solutions of NaCl and MgSO 4 dissolved in liquid water from previous studies at ambient pressure (0.1 MPa) and at 0 °C or 25 °C.…”

MAGPRIME: An Open‐Source Library for Benchmarking and Developing Interference Removal Algorithms for Spaceborne Magnetometers

“…In this work, we evaluate the performance of algorithms in the MAGPRIME library using two benchmarks. The first benchmark, denoted Benchmark A, simulates a gradiometry configuration commonly employed by modern spacecraft that depend on magnetometer measurements (Auster et al, 2008;Broadfoot et al, 2022;Kilcommons et al, 2017;Kivelson et al, 2023). Traditionally, this setup involves placing one sensor at the boom's end and another halfway down, with the presumption that both sensors reside within the far-field domain, thereby validating the single effective dipole assumption.…”

“…However, magnetic cleanliness is not always feasible, especially for low cost or mass produced spacecraft such as CubeSats. The second method is gradiometry, which uses two or more magnetometers to estimate and remove the interference signals (Jo et al, 2023;Kivelson et al, 2023;Lee et al, 2023). Ness et al (1971) proposed a gradiometry algorithm that assumes the spacecraft magnetic field as a dipole and removes it using the gradient between two magnetometers placed collinearly on a boom.…”