High-Fidelity Fluxgate Cores: Restoring a Critical Edge for Space Weather
A NASA-sponsored team at the University of Iowa is reviving and advancing the nation’s capability to perform high-fidelity magnetic field measurements essential for studying space weather. By reimagining fluxgate magnetometers—devices that quantify magnetic fields in space—the researchers are replacing a legacy ferromagnetic core once developed for the U.S. Navy and now lost to civilian manufacturing. The result is a modern, in-house process that yields cores tailored for current and future space missions.
From Legacy Materials to Modern, In-House Manufacturing
Fluxgate magnetometers work by driving a current through a drive winding on a ferromagnetic core, which alters the core’s relative permeability in response to external magnetic fields. The sensor detects the induced voltages in a sense winding, translating them into precise magnetic-field measurements. The UI team’s breakthrough lies in creating new cores without relying on the old, civilian-inaccessible processes and materials. Starting from base metal powders, the team melts custom alloys, rolls the material into thin foils, fabricates the exact core geometry, and then artificially ages the assembly with heat to optimize magnetic properties. The resulting cores are integrated into complete, flight-ready fluxgate sensors.
This end-to-end in-house workflow—design, prototyping, and manufacturing—enables rapid exploration of new sensor geometries and mission-specific configurations. The team recently developed a compact SWIM (Space Weather Iowa Magnetometer) core that builds on the MAGIC (MAGnetometers for Innovation and Capability) Tesseract design used on NASA’s TRACERS mission, but with miniaturization that preserves performance. The SWIM core’s flight readiness marks a significant milestone for a broader fleet of space weather instruments.
SWIM: A Next-Generation, Low-Footprint Magnetometer
The SWIM sensor embodies three major improvements over its MAGIC predecessor: smaller, lighter hardware; lower power draw; and a redesigned electronics topology. These changes are designed to fit on a magnetometer boom while maintaining, or even improving, measurement fidelity. In particular, the team has reduced sensor size by roughly 30 percent and can reach a sensor mass around 110 grams with a carbon-composite cover, making SWIM a strong candidate for small satellite platforms and deployable booms.
Core Design and Metallurgy
The enhanced cores come from a carefully engineered metallurgical chain: base powders are melted into alloys, rolled into thin foils, formed into the fluxgate geometry, and heat-aged to maximize permeability stability and low noise. Early testing shows that about 90 percent of produced cores achieve a noise floor that matches or surpasses legacy cores, ensuring consistent performance as production scales for SWIM and future missions.
Electronics Topology: From Analog to Digital
Beyond the core itself, SWIM introduces a modern electronics topology. The MAGIC instrument relied on an analog demodulation approach and high-end components to parse small magnetic signals amid large ambient fields. SWIM shifts to digital demodulation and uses a temperature-compensated, digital, pulse-width-modulated magnetic feedback system. This approach improves resilience in radiation-rich environments, broadens potential mission applications, and reduces reliance on fragile, high-performance parts without sacrificing measurement fidelity.
Operational Impacts: Power, Mass, and Mission Flexibility
Three smaller cores, combined with superior metallurgy, slash power consumption compared with MAGIC—nearly a factor of two reduction—while preserving the precision needed for space weather studies. Reduced heat dissipation lowers the risk of thermal gradients that can affect boom pointing, vibration, and deployment. The compact, lower-mass SWIM design also simplifies integration onto science spacecraft booms and increases the feasibility of deploying multiple sensors on distributed or swarming platforms.
Flight Opportunities and the Path Forward
The first flight opportunity for the SWIM fluxgate is on the University of Oslo’s ICI-5bis sounding rocket mission, scheduled for winter 2025/2026 from the Andøya Space Sub-Orbital range in Norway. The streamlined form factor, improved radiation tolerance, and in-house manufacturability position SWIM to support ongoing and future missions—ranging from high-altitude science flights to long-duration planetary and radiation belt explorations. The UI team envisions broader adoption of the SWIM design for future magnetometer booms, enabling more robust and economical space weather measurements across a range of mission profiles.
A Collaboration with a Clear Vision
Lead by Dr. David Miles, with support from the Heliophysics Strategic Technology Office (HESTO), the project underscores the importance of internal, end-to-end capabilities in sustaining and advancing space science instrumentation. By revisiting foundational cores with modern metallurgy and digital electronics, the UI team is not only preserving a critical measurement technology but also expanding its reach to future exploration campaigns and operational space weather sounding missions.
