Magnetic cleanliness on NanoMagSat, a CubeSats’ constellation science mission

NanoMagSat is a constellation of three identical 16U CubeSats, which aims to complement, at a much lower cost, ESA's Swarm constellation of satellites that currently monitor the Earth's magnetic field and ionospheric environment. To collect magnetic and ionospheric environment data, the CubeSats are equipped with two magnetometers, which are very sensitive to magnetic fields. Therefore, to guarantee the accomplishment of the mission and avoid unintended magnetic fields, both coming from the spacecraft and from the external environment (e.g., during integration or testing activities), degrade the performance of the magnetometers, it is essential to implement a proper magnetic cleanliness control plan. This work explains the DC magnetic cleanliness control plan at system and subsystem level, identifies the main magnetic field sources, describes the design guidelines followed on NanoMagSat as well as presents initial magnetic test results, comparing measurements with analytical and heritage estimations.