Magnetic Field Simulation and Correlated Low-Frequency Noise Subtraction for an In-Orbit Demonstrator of Magnetic Measurements

In recent years, nanosatellites have revolutionized the space sector due to their significant economic and time-saving advantages. As a result, they have fostered the testing of advanced instruments intended for larger space science missions. The case of the Magnetic Experiment for the Laser Interferometer Space Antenna (MELISA) is presented in this work. MELISA is a magnetic measurement instrument which aims at demonstrating the in-orbit performance of anisotropic magnetoresistance (AMR) sensors featuring dedicated noise reduction techniques at sub-millihertz frequencies. Such low frequency ranges are relevant for future space-borne gravitational wave (GW) detectors, where the local magnetic environment of the satellite might yield a significant contribution to the overall noise budget of the observatory. The demanding magnetic noise levels required for this bandwidth, down to 0.1 mHz, make measurements arduous. To explore sensing solutions within the H2020 European Commission Programme with the involvement of the European Space Agency (ESA), the functional performance of MELISA-III will be validated in-orbit. During operations, there is the possibility to measure the low-frequency magnetic contribution stemming from orbiting the Earth's magnetic field, which will impede the characterization of the intrinsic performance of the sensor. With the objective of minimizing excess noise during the in-flight operations, the present research aims to simulate the environmental magnetic conditions in low Earth orbit (LEO) in order to identify and subtract undesired contributions to the measurements. The in-orbit long-term magnetic fluctuations are replicated using a triaxial Helmholtz coil system. A fluxgate magnetometer (FGM) allows the correlation of the generated field with the payload measurements, leading to the subsequent subtraction. Proving the effect of this approach will facilitate the noise characterization of magnetic sensors in LEO, paving the way for the in-orbit validation of MELISA-III for use in magnetically demanding missions with long integration times.