Study on the data analysis of lunar ad planetary magnetic anomalies

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1) Spatial resolution of ER methodThe electron reflection (ER) method is thought to be one of the useful techniques for detecting the surface magnetic anomaly. We examined its spatial resolution from the observational data and the theoretical aspect. Using the 16Hz data of GEOTAIL magnetometer, the directional stability for about 500 seconds in both the solar-wind and magnetoshpere region was analyzed. As a result, the fisherian standard deviation is less than 2 degree in the tail-lobe region and 4 degree in the calm interval of the solar-wind region. However it is much higher in other region to be 15-30 degree. These directional scattering exceeds the normal Larmor raius of electrons. If we apply 16Hz sampling rate, the foot print of ER remote sensing is continuous enough for a high spatial resolution of about 1km.2) Magnetic fields along the moon orbitWe analyzed the directional stability of 20-100 Re orbit by GEOTAIL 3min-averaged data (1994 July 1-August 13 ; 44days). The histogram of fisherian standard deviations (a63) shows almost bimodal feature with peaks around 10-20 degree and 40-50 degree. The results from the 16Hz-data analyses suggest that the foot print is continuous when a63<40 degree. Therefore, at least, one third of the lunar orbit could provide an enough condition of the lunar magnetic environment for the 16Hz ER method.3) Calibration of magnetometer alignmentWe show that magnetometer alignment can be calibrated by using the Alfven wave of the solar wind for not only a spinning space craft but also tri-axial controlled one.