CHIMERA: A hybrid search coil and fluxgate magnetometer for small spacecraft missions

This three year proposal will support the development, optimization, and testing of CHIMERA - a hybrid magnetometer that simultaneously operates as both a search coil and a fluxgate. CHIMERA is expected to provide reasonable sensitivity from DC to 10 kHz from a single, compact sensor requiring only one deployable boom. This is particularly useful for small spacecraft and CubeSats, where multiple deployable booms are challenging so even modest sensitivity over this broad range is significant. The hybrid design builds on established fluxgate and search coil technology with decades of heritage operating in extreme and hostile environments. CHIMERA is aligned with the NASA Technology Roadmap in Technology Area 8.3.3 In Situ - Instruments and Sensors and will advance from TRL-3 (technology readiness level) to TRL-6. Science missions have often needed a search coil magnetometer for high frequencies and a fluxgate for the static field and low frequencies. These two instruments interfere with each other - the search coil detecting the drive signal from the fluxgate and the ferromagnetic core providing magnetic gain in a search coil distorting the field measured by the fluxgate. The two resulting deployable booms affect spacecraft control and can impinge the field of view of other instruments. A proof-of-concept laboratory prototype of CHIMERA has demonstrated how to operate a racetrack fluxgate sensor as both a fluxgate and a search coil magnetometer using essentially the same hardware already present in a typical fluxgate instrument. The two sensing techniques can operate simultaneously without interfering in a hybrid sensor engineered to accommodate both effects. The proposed project supports early career development for the PI, David M. Miles, and higher education training for one graduate student and three undergraduate research assistants. A flight-ready hybrid magnetometer enables the investigation of multiple science questions under the NASA Heliophysics overarching science goal to: "Advance our understanding of the connections between the sun, Earth, the planetary space environments, and the outer reaches of our solar system". A hybrid magnetometer is ideally suited for future missions including: a constellation follow-on to the recent funded GTOSat radiation belt CubeSat, daughter payloads deployed from the Geospace Dynamics Constellation (GDC), or small ride along spacecraft that have been suggested for future planetary missions. Magnetic field data from DC – 10 kHz from these missions would be important in addressing, respectively, three science goals identified in Solar and Space Physics: A Science for a Technological Society: SWMI Science Goal 4. Establish How Energetic Particles Are Accelerated, Transported, and Lost; SWMI Science Goal 7. Determine How Magnetosphere-Ionosphere-Thermosphere Coupling Controls System-Level Dynamics; and SWMI Science Goal 8. Identify the Structures, Dynamics, and Linkages in Other Planetary Magnetospheric Systems. We have defined three investigation objectives to ensure that the hybrid magnetometer developed under this proposal is suitable for the broad spectrum of future Heliophysics missions which require magnetic field measurements. 1) Expand the DC – 2 kHz bandwidth of the current hybrid magnetometer prototype to provide magnetic field measurements from DC – 10 kHz from a single magnetometer sensor. 2) Optimize the search coil action of the hybrid magnetometer to achieve noise and sensitivity within a factor of four of that achieved by comparably sized traditional search coil sensors (e.g., RBSP, THEMIS) 3) Scale down the hybrid magnetometer sensor to nanosatellite geometry (< 10 x 10 x 10 cm^3) while preserving scientifically useful sensitivity from DC-10 kHz. CHIMERA will enable high fidelity magnetic field studies on future SmallSat/CubeSat heliophysics missions around the Earth, the moon, and other planetary bodies. More »