Development of examination and correction system for satellite-borne fluxgate magnetometer

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For the geomagnetic field measurement by use of rocket or satellite-borne fluxgate magnetometer, correction of flight data and calibration on the ground are very impotant. I have developed an examination and correction system for magnetometer that was composed of a tri-axial Helmholtz coil, control computer, multiple power suplies, data recorder and analysis programs. A test magnetometer is fixed in the center of the Helmholtz coil. If institution value of satellite motion are given to the computer, the magnetometer data shows simulant changes correspondence to the satellite motion which are spin frequency, precessional angle and period. The computer gives commands to multiple power supplies and AC current is controled an amplitude, phase and frequency in the tri-axial coil. As a result of. the examinaction, good simulant output data is obtained for a test magnetometer. The output data is acquired by data recorder and is transmitted to the host computer. By the analysis programs, the correction parameters are determined. The parameters are precise angles between non-rectanglar sensor axes, sensor sensitivity for magnetic intensity and magnetic offset field from satellite body or instruments. The programs are composed of the least square method and coordinate transformation between the non-rectanglar and rectanglar system. The correction was estimated by use of the "AKEBONO" scientific satellite data. The tri-axial fluxgate magnetometer sensors boarded on the 5m-extension mast and 32Hz-sampled data of geomagnetic field vector were obtained. By use of the correction system, itwas able to determine that each sensor angle were 89.902-89.962 degrees and magnetic offset were 22-189 nT. In consequence, it is confirmed that the examination coil equipment and the analysis programs are very effective for satellite-borne magnetometer correction.