深空探测中磁强计在轨标定研究进展

Research progress on in-flight calibration of the magnetometer in deep space exploration

磁场测量是深空探测的重要任务之一,高精度的磁场测量对研究行星宜居性、空间等离子体环境等具有重要意义.磁通门磁强计是空间探测任务中最广泛使用的仪器之一.然而其磁补偿会随时间缓慢变化,因此,在卫星飞行期间需要定期对磁强计的磁补偿实施在轨标定.本文综述了基于空间物理现象对星载磁强计实施在轨标定的方法.根据计算磁补偿的方式,这些方法可分为两类.第一类方法通过公式计算磁补偿,如基于阿尔芬波动特征的Belcher方法、Hedgecock方法和Davis-Smith方法,以及一维和三维磁镜模方法;这类方法中,Davis-Smith方法被认为是计算磁补偿的最优方法.第二类方法通过概率获取磁补偿的最优解,该类方法被称为新一代在轨标定技术,目前已发展出六种算法;该技术可使用阿尔芬波动、磁镜结构和电流片中的一种或多种现象来实施在轨标定,另外,该技术也可以使用足够数据量(如4小时)的任意行星际磁场数据来计算磁补偿.与Davis-Smith方法相比,新一代在轨标定技术具有很好的兼容性(可同时使用不同的物理现象)和拓展性.除了太阳风,该技术还能在火星磁鞘中实施在轨标定.目前,该技术已为“天问一号”环绕器的磁场数据提供标定服务.

Magnetic field measurements play a crucial role in deep space exploration,contributing significantly to our understanding of planetary habitability and the space plasma environment.Among the various instruments employed in space exploration missions,the fluxgate magnetometer stands out as a widely used tool.However,its zero offset undergoes gradual changes,necessitating regular in-flight calibration.This article comprehensively reviews in-flight calibration methods for spaceborne magnetometers in deep space exploration,leveraging physical phenomena inherent to the space environment.The methods for calculating the zero offset can be divided into two categories.The first group employs formulas,including the Belcher method,Hedgecock method,Davis-Smith method,and both one-dimensional and three-dimensional mirror mode methods.Notably,the Davis-Smith method emerges as the optimal choice among these approaches.The second group employs probability-based solutions,constituting the in-flight calibration technology of the new generation,which encompasses six algorithms.This innovative technology utilizes phenomena such as Alfvén waves,magnetic mirror structures,and current sheets for in-flight calibration.Moreover,this technology can leverage interplanetary magnetic field data,specifically requiring a sufficient data amount(e.g.,4 hours)to calculate the zero offset.Compared to the Davis-Smith method,the in-flight calibration technology of the new generation demonstrates good compatibility,allowing for the simultaneous use of different physical phenomena,and scalability.This technology extends its applicability beyond solar wind,enabling in-flight calibration in the Martian magnetosheath.Currently,this technology has successfully provided calibration services for the magnetic field data of the Tianwen-1 orbiter.