Accurate magnetic field measurements by fluxgate magnetometers onboard spacecraft require ground and regular in-flight calibration activities. Therewith, the parameters of a coupling matrix and an offset vector are adjusted; they are needed to transform raw magnetometer outputs into calibrated magnetic field measurements. The components of the offset vector are typically determined by analyzing Alfvénic fluctuations in the solar wind if solar wind measurements are available. These are characterized by changes in the field components, while the magnetic field modulus stays constant. In this paper, the following question is answered: how many solar wind data are sufficient for accurate fluxgate magnetometer offset determinations? It is found that approximately 40 h of solar wind data are sufficient to achieve offset accuracies of 0.2 nT, and about 20 h suffice for accuracies of 0.3 nT or better if the magnetometer offsets do not drift within these time intervals and if the spacecraft fields do not vary at the sensor position. Offset determinations with uncertainties lower than 0.1 nT, however, would require at least hundreds of hours of solar wind data.

中文翻译：

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有多少太阳风数据足以准确确定磁通门磁强计偏移量？

航天器上的磁通门磁力计要进行准确的磁场测量，需要进行地面和定期的飞行中校准活动。由此，调整耦合矩阵和偏移矢量的参数。它们需要将原始磁力计的输出转换为校准的磁场测量值。如果可以获得太阳风的测量值，则通常通过分析太阳风中的Alfvénic波动来确定偏移矢量的分量。这些特征在于场分量的变化，而磁场模量保持恒定。在本文中，将回答以下问题：多少个太阳风数据足以准确确定磁通门磁强计偏移量？发现大约40 h的太阳风数据足以实现0.2  nT的偏移精度，如果磁力计的偏移量在这些时间间隔内没有漂移并且航天器磁场在传感器位置不变，则约有20 h即可达到0.3 nT或更高的精度。 。但是，不确定性低于0.1 nT的偏移量确定至少需要数百小时的太阳风数据。