A METHOD OF CALIBRATING MAGNETOMETERS ON A SPINNING SPACECRAFT

This paper describes a procedure for quantifying and compensating for angular offsets and slow-varying drifts associated with a flux-gate ma gnetometer onboard a spinning spacecraft. Such magnetometers have been flown on numerous spacecraft such as IMP-8, DE-1, and ISTP/GEOTAIL, a nd similar instruments are currently proposed to fly on the ISTP/WIND spacecraft. Consequently, slight geometric misalignment of the sensor from their chosen axes will create errors in the measured signal. Thes e misalignments can be quantified using perturbation theory and compen sated in the data analysis process. The technique is applicable to mag netometers on spinning spacecraft. Also, over long time periods, the m agnetometer will develop slight drifts in the electronic components, a nd these too can be quantified in the data analysis process. We shall discuss a technique that quantifies and compensates for such perturbat ions from the measurements. The technique has been successfully applie d for the last sixteen years to IMP-8 magnetometer data and more curre ntly to the GEOTAIL magnetometer data, and can be applied in a general way to measurements from any magnetometer onboard a spinning spacecra ft. Further improvements in the technique will also be discussed.