First In Situ Measurements of the Prototype Tesseract Fluxgate Magnetometer on the ACES-II Low Sounding Rocket

Abstract. Ongoing innovation in next generation fluxgate magnetometry is important for enabling future investigations of space plasma, especially multi-spacecraft experimental studies of energy transport in the magnetosphere and the solar wind. Demonstrating the spaceflight capability of novel designs is an important step in the instrument development process; however, large-scale satellite missions are often unwilling to accept the risks of an instrument without flight heritage. The Tesseract – a novel fluxgate magnetometer sensor design-had an opportunity for an inaugural spaceflight demonstration on the ACES-II sounding rocket mission, which launched from Andøya Space Center in Andenes, Norway, in November 2022. Tesseract’s design takes advantage of a new racetrack core geometry to create a sensor that addresses some of the issues that contribute to instability in more traditional ring core designs. Here we present the design of a prototype fluxgate magnetometer based on the new Tesseract sensor, its preflight characteristics, and an evaluation of its inflight performance aboard ACES-II. We find that the magnetic field measured by Tesseract over the course of the flight was in strong agreement with both the onboard ACES II reference ring core fluxgate magnetometer and the predictions of a geomagnetic field model. The Tesseract based magnetometer measured signatures of field aligned currents and potential Alfvén wave activity as it crossed an active auroral arc, we conclude that it performed as expected. Tesseract will be flown on the TRACERS Small Explorers (SMEX) satellite mission as part of the MAGIC technology demonstration currently scheduled to launch in 2025.