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Precision Magnetometers for Aerospace Applications

James S. Bennett, Brian E. Vyhnalek, Hamish Greenall, Elizabeth M. Bridge, Fernando Gotardo, Stefan Forstner, Glen I. Harris, Félix A. Miranda, Warwick P. Bowen

arXiv:2106.15843v1physics.app-phphysics.space-ph

TL;DR

Aerospace magnetometry serves planetary science and aerospace applications, but established instruments can be poorly suited to emerging smaller platforms. This review surveys existing and emerging magnetometers and their operating characteristics, emphasizing optical readout. It identifies optical readout as a route toward improved sensitivity and size, weight, and power performance for next-generation devices.

  • Problem

    Emerging aerospace applications involving smaller platforms require lower size, weight, and power while maintaining equivalent or enhanced performance, whereas many established magnetometers are near physical limits.

    Source: §V · p. 13

  • Method

    The review surveys established and emerging magnetometer platforms, compares operational parameters, and examines optical-readout atomic, diamond-defect, and optomechanical devices.

    Source: §I · p. 1, §V · p. 13

  • Results

    Optical readout is identified as a key route toward improved sensitivity and SWaP for next-generation magnetometers.

    Source: §V · p. 13

  • Takeaways & Limitations

    Optical magnetometers’ sensitivity and miniaturization without cryogenic cooling, alongside reduced power consumption, hold promise for Earth-based and extraplanetary aerospace applications.

    Source: §I · p. 1

    Heritage proton-precession and optically pumped magnetometers can have mass above 1 kg, power requirements above 10 W, and volume above 100 cm3.

    Source: §III · p. 11

Abstract

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Aerospace technologies are crucial for modern civilization; space-based infrastructure underpins weather forecasting, communications, terrestrial navigation and logistics, planetary observations, solar monitoring, and other indispensable capabilities. Extraplanetary exploration -- including orbital surveys and (more recently) roving, flying, or submersible unmanned vehicles -- is also a key scientific and technological frontier, believed by many to be paramount to the long-term survival and prosperity of humanity. All of these aerospace applications require reliable control of the craft and the ability to record high-precision measurements of physical quantities. Magnetometers deliver on both of these aspects, and have been vital to the success of numerous missions. In this review paper, we provide an introduction to the relevant instruments and their applications. We consider past and present magnetometers, their proven aerospace applications, and emerging uses. We then look to the future, reviewing recent progress in magnetometer technology. We particularly focus on magnetometers that use optical readout, including atomic magnetometers, magnetometers based on quantum defects in diamond, and optomechanical magnetometers. These optical magnetometers offer a combination of field sensitivity, size, weight, and power consumption that allows them to reach performance regimes that are inaccessible with existing techniques. This promises to enable new applications in areas ranging from unmanned vehicles to navigation and exploration.

I. INTRODUCTION

The review surveys established and emerging aerospace magnetometers, covering planetary science, Earth atmosphere and orbit, and optical-readout technologies. Optical magnetometers are a particular focus because their sensitivity and miniaturization may suit emerging aerospace applications.

I. INTRODUCTION

  • Magnetometers support studies of Earth, other planets, and the heliospheric field, as well as aerospace tasks such as attitude determination and magnetic geological surveying.The review updates earlier overviews to include extraplanetary, Earth-atmosphere, orbital, and emerging applications.Source: §I · p. 1
  • Optical-readout atomic, diamond-defect, and optomechanical magnetometers combine high sensitivity without cryogenic cooling with miniaturization and reduced power consumption.The review identifies these attributes as promising for Earth-based and extraplanetary aerospace applications.Source: §I · p. 1

A. Interplanetary science missions

  • Precise magnetic measurements help investigate celestial bodies and space-physics processes involved in planetary and solar-system evolution.Source: A. Interplanetary science missions · p. 2
  • Interplanetary magnetometers map fields and characterize planets, while also supporting atmospheric studies and indirect searches for liquid water.Source: A. Interplanetary science missions · p. 2
  • Fluxgate magnetometers are a common spacecraft choice for proven reliability and compliance with mission weight and power requirements, though extreme environments, surface missions, and multi-platform missions may call for other designs.Table I summarizes spacecraft magnetometer specifications.Source: A. Interplanetary science missions · p. 2, Table I · p. 2
  • Fluxgates measure vector fields through field-dependent saturation imbalance in a magnetically permeable core, with sensitivity around 10 pT/Hz^1/2 and resolution around 5 pT at DC.Their sensitivity is limited by core Barkhausen noise and low-frequency 1/f noise.Source: A. Interplanetary science missions · p. 2

1. Mars Atmosphere and Volatile Evolution (MAVEN)

MAVEN and Cassini illustrate spacecraft magnetometer configurations tailored to their mission measurements. MAVEN used boomlet-mounted fluxgates for Mars studies, while Cassini combined fluxgate and helium instruments on a long boom.

1. Mars Atmosphere and Volatile Evolution (MAVEN)

  • MAVEN’s mission included studying atmospheric escape and assessing the upper atmosphere, ionosphere, and solar-wind interactions.Source: §1 · pp. 2–3
  • MAVEN’s paired ring-core fluxgates, mounted about 5.6 m from the spacecraft body on solar-array boomlets, supported investigation of solar-wind interactions and atmospheric escape at Mars.The sensors had Martian-field ranges of ±512 nT and ±2048 nT, with digital resolutions of 0.015 nT and 0.062 nT, respectively.Source: §1 · p. 3, Figure 1 · p. 3

2. Cassini

  • Cassini measurements mapped Saturn’s magnetosphere and studied its internal field and electromagnetic interactions with moons, rings, and surrounding plasma.Source: §2 · p. 3
  • Cassini combined three-axis fluxgate and vector helium magnetometers, with a scalar helium mode for in situ absolute calibration of the fluxgate.An 11 m boom placed the vector/scalar helium sensor at its end and the fluxgate halfway along, helping separate spacecraft stray fields from observations.Source: §2 · p. 3

3. Juno

Juno and planned interplanetary missions use magnetometers to characterize planetary magnetic environments and address mission-specific science goals. Smaller probes and airborne missions also motivate interest in more compact instruments.

3. Juno

  • Juno uses two independent triaxial ring-core fluxgate sensors with co-located star trackers on a 4 m boom, enabling magnetic-environment mapping around Jupiter.Its nominally most sensitive range has 0.0488 nT resolution.Source: §3 · p. 4

B. Future interplanetary missions

  • Future exploration includes smaller platforms such as CubeSats, NanoSats, and PocketQubes, as well as rovers and rotorcraft.Source: B. Future interplanetary missions · pp. 4–5
  • Psyche’s two-sensor fluxgate gradiometer is intended to detect and measure the asteroid’s magnetic field, which would confirm whether it is a planetesimal core.The sensors are located at the middle and outer end of a magnetometer boom.Source: B. Future interplanetary missions · p. 5
  • JUICE will use boom-mounted inbound and outbound fluxgate sensors to characterize Jupiter’s field, its interaction with Ganymede, and icy-moon subsurface oceans.Source: B. Future interplanetary missions · p. 5
  • Europa Clipper’s triaxial fluxgate magnetometer will measure Europa’s field strength and direction to help determine ocean depth and salinity.Source: B. Future interplanetary missions · p. 5
  • A proposed CubeSat fluxgate network could characterize Europa’s deep ocean, while Dragonfly omits magnetometers because of size and weight restrictions, underscoring the need for miniaturized efficient sensors.Proposed magnetometer-equipped drone missions also target Enceladus and Titan.Source: B. Future interplanetary missions · p. 5

C. Applications in Earth atmosphere and orbit

Magnetometers serve Earth-atmosphere and orbital aerospace applications, from satellite attitude determination to geomagnetic surveys using unmanned aerial vehicles.

C. Applications in Earth atmosphere and orbit

1. Geostationary Operational Environmental Satellites (GOES)

GOES satellites use magnetometers to monitor geomagnetic storms and related effects, while the series’ fluxgate configurations evolved across successive generations.

1. Geostationary Operational Environmental Satellites (GOES)

  • GOES magnetometers monitor Earth’s magnetic field, supporting characterization of geomagnetic storms, energetic particles, and magnetospheric and ionospheric effects.Their measurements also matter for GPS scintillation, power-grid effects, high-frequency radio communications, low-Earth-orbit drag, and rocket launch decisions.Source: §1 · pp. 5–6
  • GOES fluxgate configurations progressed from biaxial sensors on 6.1 m booms to triaxial systems, with later designs improving resolution to about 0.016 nT.The series moved through 3 m and 8.5 m boom configurations; GOES-N/O/P favored 0.03 nT resolution over the preceding ±1000 nT range.Source: §1 · pp. 6–7
  • Similar satellite networks have been proposed to supplement radar early-warning systems by detecting magnetic anomalies before earthquakes.One proposal is the Global Earthquake Satellite System (GESS).Source: §1 · p. 7

2. Magnetometers onboard micro- and nanosatellites

Micro- and nanosatellites face constraints on attitude determination because auxiliary sensors can be too bulky and power-consuming, while onboard magnetic disturbances complicate precise measurements.

2. Magnetometers onboard micro- and nanosatellites

  • Small satellites may need magnetometer-only attitude determination, but a three-axis magnetometer alone usually cannot provide three-axis attitude information.Onboard magnetized objects and current loops also distort measurements, while the auxiliary sensors used on larger satellites can be too bulky and power-consuming for CubeSats.Source: §2 · p. 7
  • Precise attitude determination for increasingly sophisticated small-satellite missions is complicated by magnetic bias noise from the interaction of Earth’s field with satellites’ large magnetic moments and small inertia.Proposed approaches include estimating the interaction with a gyroscope and Kalman filter, comparing readings with an Earth-field model, or calibrating disturbances; the model comparison is computationally expensive, and multiple magnetometers require further SWaP reduction.Source: §2 · p. 8
  • Reduced-SWaP fluxgate magnetometers have been developed and deployed on Dellingr, and were planned for the SPORT CubeSat.Miniaturized FGMs are also intended for Gateway HERMES; two lower-SWaP magneto-inductive sensors on the platform will detect and subtract noise from its power and propulsion module.Source: §2 · pp. 8–9
  • Magneto-inductive sensors measure field-dependent changes in an oscillation circuit’s frequency; the commercial RM3100 is about 15 mm3, uses about 0.1 W, and has around 20 nT resolution.Its stated dynamic range is -800 µT to +800 µT, with a sample rate above 400 Hz.Source: §2 · p. 9
  • A self-calibrating hybrid pairs a vector fluxgate with a scalar atomic magnetometer to address fluxgate drift, with small SWaP suited to constellation missions.Such constellations use multiple CubeSats for multi-point observations.Source: §2 · p. 9
  • A compact dual-sensor vector AMR magnetometer, MAGIC, reports 3 nT sensitivity in a 0–10 Hz band, ±57,500 nT measurement range, 104 g mass, and 0.14–0.5 W power.AMR/GMR sensors are alternatives to fluxgates for small satellites; MAGIC has flown on the TRIO-CINEMA CubeSat mission.Source: §2 · p. 9

3. Navigation in the Earth’s atmosphere

Magnetic measurements support aircraft heading and proposed navigation in GPS-degraded or -denied settings, where aerial surveys can map local geomagnetic variations.

3. Navigation in the Earth’s atmosphere

  • Aircraft have long used magnetometers for heading, with proton-precession instruments historically used for local geomagnetic observations.Overhauser magnetometers reduce the power burden of proton-precession designs through RF pumping and have flown on satellites, including Ørsted at about 20 pT/Hz^1/2 sensitivity, 3 W, and 1 kg.Source: §3 · p. 9
  • Matching local magnetic-field variations from crustal rock formations to a detailed Earth magnetic-field map has been proposed for navigation in GPS-degraded or -denied environments.Ground proton-precession and Overhauser measurements are impractical for the required spatial resolution and coverage, so aerial surveys are needed.Source: §3 · p. 9
  • Lockheed Martin’s Dark Ice uses an NV-center vector magnetometer for magnetic navigation, with spatial resolution down to about 200 m depending on flight altitude and SWaP suited to small UAVs.Source: §3 · p. 10

4. Magnetometers in manned aerial vehicles

Manned aircraft support high-sensitivity surveys with larger, higher-power instruments, while UAV surveys offer low-altitude access and spatial resolution but face a sensitivity-versus-SWaP constraint.

4. Magnetometers in manned aerial vehicles

  • Manned vehicles are used for geological surveys, unexploded ordnance detection, and magnetic anomaly detection; their size and power support high-sensitivity airborne systems such as the SQUID-based UXOMAX.UXOMAX is a tensor magnetic-gradient measurement system.Source: §4 · p. 10
  • SQUID magnetometers offer sub-fT/Hz^1/2 sensitivity, high dynamic range, spatial resolution down to nanometres, and DC-to-GHz bandwidth, but require cryogenic operation and are incompatible with low-SWaP applications.They have nevertheless been used on planes and helicopters for nondestructive archaeology and geomagnetic evaluation.Source: §4 · p. 10

5. Magnetometers in unmanned aerial vehicles

  • UAV surveys provide few-meter spatial resolution, high sensitivity from low flight altitude, and access to rugged terrain, but fluxgates are currently the most sensitive sufficiently low-SWaP option for typical UAVs and are several orders less sensitive than SQUIDs.UAV surveys are particularly efficient for small targets such as unexploded ordnance and landmines.Source: §5 · p. 10
  • An optical-readout magnetostrictive interferometer has low SWaP, about 110 g and under 3 W, with 10 pT/Hz^1/2 sensitivity over 1–100 Hz and dynamic range above 100 µT.It uses magnetostrictive strain to change the relative optical path length and phase in a fibre-optic interferometer.Source: §5 · p. 10
  • Hall magnetometers measure AC and DC fields but are less accurate than other precision sensors, so aerospace uses include safety interlocks, rotation gauges, and proximity sensors rather than scientific instrumentation.Their peak sensitivity is around 1 nT/Hz^1/2.Source: §5 · p. 10

III. EMERGING MAGNETOMETERS

Emerging magnetometers address the size, weight, and power limits of heritage instruments, especially for small aerospace platforms. Atomic magnetometers offer high sensitivity and compact options, while SERF operation trades dynamic range for sensitivity.

III. EMERGING MAGNETOMETERS

  • Heritage instruments remain useful, but their mass, power, and volume constrain use on small craft, motivating reductions in size, weight, and power without sacrificing performance.Proton-precession and optically pumped magnetometers can exceed 1 kg, 10 W, and 100 cm^3; fluxgates also experience scale-factor drift and voltage offsets with time and temperature.Source: §III · p. 11

A. Atomic magnetometers (including SERF)

  • Atomic magnetometers infer magnetic fields from field-driven electron precession detected through changes in transmitted light, with sensitivities as high as 160 aT Hz^1/2.They can provide millimeter-scale spatial resolution and vector measurements, but some designs have low dynamic range and require shielding or closed-loop operation.Source: A. Atomic magnetometers (including SERF) · p. 11
  • A proposed 87Rb atomic scalar magnetometer has a 1 mm^3 vapor cell, weighs less than 0.5 kg, uses less than 1 W, and achieves 15 pT/Hz^1/2 at 1 Hz.Its sensitivity is comparable with high-sensitivity heritage technologies, and the authors identify it as a viable SmallSat option.Source: A. Atomic magnetometers (including SERF) · p. 11
  • SERF devices improve absolute sensitivity with dense, heated vapor but sacrifice dynamic range, requiring magnetic shielding or active cancellation and increasing power needs.They cannot tolerate fields around the microtesla scale sensed by standard vapor cells.Source: A. Atomic magnetometers (including SERF) · p. 11

B. Optomechanical magnetometers

Optomechanical and atomic-defect magnetometers use optical readout to detect magnetic fields, with different operating mechanisms and practical constraints. Optomechanical devices combine competitive sensitivity with low power, while NV centers offer high spatial resolution and broad operating frequencies.

B. Optomechanical magnetometers

  • Optomechanical cavities deform in magnetic fields, shifting their optical resonance; magnetostrictive coatings or fillings commonly generate the deformation.Some designs instead respond to field gradients through dipole forces or enhance magnetostrictive response using ferromagnetic resonance.Source: B. Optomechanical magnetometers · p. 12
  • 26 pT/Hz^1/2 at 10.523 MHz is the best demonstrated optomechanical field sensitivity, competitive with similarly sized SQUIDs without bulky cryogenics.These devices do not require magnetic shielding, typically have dynamic ranges around 100 µT, and use about 50 µW of optical power.Source: B. Optomechanical magnetometers · p. 12
  • Managing stress in magnetostrictive thin films and reducing low-frequency laser noise are key challenges in integrating optomechanical devices into low-SWaP packages.The review identifies potential uses on small orbital platforms, extraterrestrial rovers, and other unmanned vehicles.Source: B. Optomechanical magnetometers · p. 12

C. Magnetometers based on atomic defects in solids

  • NV centers in diamond detect magnetic fields through field-dependent ground-state splitting, measured by driving transitions with microwaves and observing dips in emitted light.Single-defect sensors provide high spatial resolution; demonstrated sensitivities reach 0.9 pT/Hz^1/2, with operation from DC to a few gigahertz.Source: C. Magnetometers based on atomic… · p. 12
  • NV magnetometry has only recently moved beyond the laboratory, and near-commercial options remain limited.The review names Lockheed Martin’s Dark Ice as an example.Source: C. Magnetometers based on atomic… · p. 12

IV. BRIEF SUMMARY

The review compares magnetometers across sensitivity, size, power, and frequency, finding trade-offs among technologies rather than a universal choice. Optical-readout devices often pair strong sensitivity with favorable size or power characteristics, but selection depends on application requirements.

IV. BRIEF SUMMARY

  • Optical-readout and superconducting magnetometers are almost universally more sensitive than conventional or electronic devices of comparable size.Current optomechanical, NV, and SERF sensors are approximately two to three orders of magnitude above their sensitivity limits, while some heritage technologies are already at theirs.Source: §IV · pp. 12–13
  • For low-power applications needing intermediate sensitivity, optomechanical, NV, and chip-scale electronic sensors are most appropriate.Figure 4’s colored regions exclude support-system power; NV power needs are linked to light-collection efficiency, which is currently low and may improve.Source: §IV · p. 13
  • Operating-frequency ranges do not indicate typical bandwidth or imply that one device can be tuned across its entire stated range.Low-frequency noise can reduce sensitivity near DC, while optomechanical and SQUID magnetometers can operate up to the VHF range for potential magnetic-antenna applications.Source: §IV · p. 13
  • No magnetometer technology suits every application; deployment requires weighing sensitivity, power, frequency, size, bandwidth, drift, and dynamic range.The review explicitly cautions against a “one size fits all” choice.Source: §IV · p. 13

V. CONCLUSIONS

The review surveys aerospace and space-based magnetometer applications, existing platforms, and emerging devices. It identifies optical readout as a route toward improved sensitivity and SWaP in next-generation instruments.

V. CONCLUSIONS

  • Emerging small-platform applications require lower size, weight, and power alongside equivalent or enhanced performance, while many existing magnetometers approach physical performance limits.The review highlights developing magnetometers and the applications they may enable, while noting that established platforms will continue to be used and developed.Source: §V · p. 13
  • The review compares magnetometer classes across sensitivity, power consumption, frequency range, and sensor size, identifying optical readout as a key route to improved sensitivity and SWaP.The authors describe this as a route for next-generation devices.Source: §V · p. 13
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