The study presents a novel design for a compact space search coil magnetometer (SSCM) tailored for space missions that demand low mass and power consumption while preserving sensor performance. Search coil magnetometers (SCMs) are critical instruments used to detect time-varying magnetic fields in space, essential for understanding electromagnetic wave phenomena near Earth and the Moon.
Conventional SCMs often trade off increased sensitivity against rising sensor mass and electronic power needs. Addressing this challenge, the presented SSCM design aims to integrate a lightweight sensor core and low-power electronics to produce a system suitable for resource-constrained space platforms, including CubeSats.
Fundamentals and Design Constraints of SCMs in Space Applications
Search coil magnetometers operate by converting magnetic field fluctuations into electrical signals using a coil and a magnetic core. The sensitivity and bandwidth of SCMs hinge largely on the properties of the coil winding and core design. Traditionally, enhancing sensitivity involves increasing core size or winding turns, which invariably adds mass and complicates spacecraft accommodation.
In space applications, where platform resources such as weight and power are tightly regulated, this creates stringent design constraints. Prior spaceborne SCMs have tended towards large cores and high-power amplifiers to meet mission needs, highlighting the necessity for a more compact, efficient approach.
Advanced Sensor and Electronics Architecture
The SSCM integrates a three-axis sensor employing a rolling-sheet magnetic core measuring 230 mm in length and 12,000 wire turns, distributed across five bobbins. This rolling-sheet core adopts a thin rolled-metal sheet as the magnetic core, which reduces sensor mass without compromising magnetic properties. Copper windings are neatly segmented over the bobbins, interconnected via printed circuit boards (PCBs) that serve both electrical and mechanical functions. The PCB implementation enhances assembly reproducibility and mechanical robustness while reducing structural complexity.
A key innovation in electronics is the use of an application-specific integrated circuit (ASIC)-based sensor amplifier. Fabricated with a 180 nm process, the ASIC features a dual-stage architecture providing 80 dB of total voltage gain and incorporates radiation-tolerant design elements and temperature compensation feedback loops. This circuit is compact (1.7 mm × 0.6 mm die size) and consumes significantly less power compared to conventional commercial operational amplifiers, achieving a 12.5% power reduction at 3.92 W under a 28 V input.
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The SSCM system’s control electronics (SCE) house signal conditioning and digital processing components using a modular 1U CubeSat form factor. The digital board includes a Radix-22 FFT algorithm implementation, facilitating on-board spectral analysis with efficiency. An ongoing development involves migrating FFT processing to a specialized ASIC fabricated at 65 nm to further reduce system-level power consumption.
Rigorous Ground-Based Performance and Calibration Methodologies
Performance validation employed ground-based testing inside magnetically shielded environments. Frequency response and noise measurements utilized a triple-layer mu-metal chamber with a calibrated solenoid generating known magnetic fields. Noise equivalent magnetic induction was derived by dividing output voltage noise spectra by the frequency-dependent sensor transfer function. Special three-axis tests quantified orthogonality and crosstalk among sensor axes by subjecting the sensor to controlled sinusoidal magnetic fields and rotating tests inside uniform fields.
Environmental robustness was confirmed through vibration and thermal cycling tests replicating realistic space launch and on-orbit conditions. Vibration tests involved sine sweep, random vibration profiles aligned with lunar orbiter launch standards, applied along orthogonal directions relative to the boom structure. Coil resistance was continuously monitored to detect mechanical integrity issues, and frequency response tests post-environmental exposure verified functional stability.
Performance Results and Comparative Evaluation
The SSCM achieved a stable and consistent frequency response over the 10 Hz to 20 kHz range aligning with the mission requirements. The system-level noise floor measured yielded a noise-equivalent magnetic induction of approximately 33 fT/√Hz at 1 kHz under laboratory conditions, validating the low-noise ASIC amplifier and sensor design. Cross-axis crosstalk was minimal, with measured orthogonality confirming reliable three-axis vector measurements.
Environmental tests verified no mechanical or electrical anomalies; resonance frequency shifts due to vibration were under 5%, indicating strong structural resilience. Table comparisons with heritage spaceborne SCMs revealed the SSCM’s advantages in core length to sensor mass ratio (0.23 m core with 0.12 kg sensor mass) and integrated system-level power consumption (3.92 W), reflecting efficient use of onboard resources despite encompassing digitization and processing electronics. Although the overall power is higher than some earlier systems reporting preamplifier-only values, the SSCM provides a comprehensive suite within constrained mass and power budgets for small satellite platforms.
Future Directions
Future work includes completing the ASIC-based FFT processor integration for further power optimization and advancing the SSCM design towards flight qualification. This study provides a practical and scalable approach for broadband SCM implementation in future space exploration missions under strict payload constraints.
Journal Reference
Jang Y., Jin H., et al. (2026). Design of a Compact Space Search Coil Magnetometer. Sensors. 2026; 26(8):2415. DOI: 10.3390/s26082415, https://www.mdpi.com/1424-8220/26/8/2415