Along-track Calibration of the Zhurong Rover Magnetometer

As part of the Chinese Tianwen-1 mission, the Zhurong Rover began its scientific investigation in the southern Utopia Planitia after its successful landing in 15 May, 2021. The Zhurong Rover magnetometer(RoMAG), one of the six payloads onboard the rover, includes two identical high-sensitivity triaxial fluxgate magnetometers and can implement mobile magnetic measurements on the surface of Mars. Although a rover magnetic compensation procedure was conducted to remove the magnetic interferences pre-launch, due to the different state of the payloads and electric power system such as the solar panel, an along-track calibration of the magnetometer is necessary to obtain a more accurate Martian magnetic field. Two methods, mast yaw rotations and Rover yaw rotations were utilized separately to determine the Martian horizontal magnetic components. Results show that the Martian horizontal magnetic components determined by the two methods are in good agreement, with the root mean square deviation less than 2.0 nT. The vertical component was also constrained through the pitch movements of the mast by assuming the interferences field distributes like a dipole field. A linear correlation between magnetic field measurements and the solar array currents was derived to calibrate the body field during the regular exploration. We conclude that more accurate measurements could be made when applying the calibration results in the magnetic survey on the surface of Mars.