L-MAG: A Temperature-Stabilized Fluxgate Magnetometer System for Long-Term Lunar Surface Observatories

Lunar magnetic field investigation connects the interior, the surface, and the space environment of the Moon. Measuring and understanding the lunar magnetic field at different length-scales and time-scales is of critical importance to understand the bulk water content and temperature profile in the lunar mantle, the existence and properties of a partial melt layer above the lunar core, the size of the lunar core, the origin of volatiles on the lunar surface, and the origin and properties of the past lunar dynamo, all of which are intimately connected to the origin of the Earth-Moon system and the subsequent thermal-chemical-environmental evolution of the Moon. The surface of the Moon, however, is a challenging environment, including contrasting temperatures between lunar day and lunar night, dust, and surface charging.

 

Here we report our progress in the designing, building, and testing of a temperature-stabilized fluxgate magnetometer (FGM) system for long-term operations on the surface of the Moon. We refer to this FGM system configuration as L-MAG. The sensor design draws heritage from those onboard the NASA Magnetospheric Multiscale (MMS) mission, InSight Mars Lander, the Europa Clipper mission, and most recently the TRACERS mission. One of the key improvements is a magnetically clean AC heater that directly surrounds the FGM sensor, improving power efficiency and responsiveness compared to Europa Clipper Magnetometer’s distant heater pod. Thermal losses are reduced with a low-emissivity enclosure and lightweight Kapton flex harness. The heater system is designed to yield a temperature stability of ± 0.1 degrees °C around two set-point temperatures (day and night) to further reduce long-term drift, allowing the inference of lunar induction responses at periods of  10⁵ seconds and longer, necessary to probe the lower lunar mantle and core. This power efficient FGM design will be compatible with installation onto a lunar lander or placed on the surface of the moon by an astronaut. Our L-MAG system will significantly improve measurement capabilities for upcoming lunar science missions including those via the Commercial Lunar Payload Services (CLPS) and via Artemis astronaut deployments.