In-flight calibration of the spaceborne fluxgate magnetometer in the Martian magnetosheath

In-flight calibration of the zero offset is crucial for ensuring high-precision measurement of the spaceborne fluxgate magnetometer. Tianwen-1 is China’s first Mars mission, and its orbiter will remain out of the solar wind for tens of days each year. Previous in-flight calibration methods might not be suitable for this orbiter during such a period. Recently, a new method was proposed by Wang GQ (2022b), which we refer to as the Wang method II for ease of description. Here, we test the performance of this method in the Martian magnetosheath by using magnetic field data measured by the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft. We find that the accuracy of the Wang method II is affected by the number of magnetic field subinterval events, the eigenvalues of the minimum variance analysis for each event, and the position of the spacecraft in the magnetosheath. The estimated zero offset varies over a period of ~27 days and has a 57.3% probability of accuracy within 2.0 nT. After being smoothed with a temporal window of 27 days, the zero offset has a 48.4% (99.3%) probability of accuracy within 1.0 (2.0) nT. Our tests suggest that the Wang method II provides an option for the Tianwen-1 orbiter to perform in-flight calibration when the orbiter remains out of the solar wind for an extended period of time.