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moving the antenna’s sub-reector mirror.e data from the ight experiment showed good agreement with those obtained from the initial check within the 170 km range from the center of the beam, and the deviation remained within 0.5 dB even at a 240 km distance from it. e agreement between the ight experi-ment data and initial check-out has proved the sustained accuracy of WINDS since its launch 8 years ago. is ex-periment has also proved that the ight experiment data taken with its measurement point moving uninterrupted agrees well with those from single-point measurements gained by moving the antenna’s sub-reector.(b)Antenna tracking characteristicsFigure 10 shows a gure-of-eight ight route and the received power levels mapped on it. e blue sections in-dicate lowered received power, where the plane is ying in the east-west direction. Because the satellite is located to the south of the plane, banking of the plane gives rise to larger elevation angle variations of the earth station when it is ying in the west-east direction than in other direc-tions. Figure 11 shows the time uctuations of azimuth and elevation angle during the gure-of-eight ight. From the gure, it can be seen that the error is 0.2° at the maximum, meeting the criterion for tracking accuracy, i.e. no greater than ±0.5°. Figure 12 shows time uctuations of elevation FiF9　Antenna pattern of MBA Chubu beamxMeasurementMeasurmentat initial check outNot connection172 km0-1-2-3-4-5-6-7-8Relativepower [dBm]FiF11Time variation of angular error during the figure-of-eight flightFiF8　Variations of received power during a straight flightNot connectionCenter of beamReceived power [dBm]Measurement time [s]FiF10Figure-of-eight flight pattern used to study antenna tracking characteristicsLongitude LatitudeRecived power [dBm]FiF12Time variation of elevation angle and received power during figure-of-eight flightRecived power [dBm]Measurement time [s]Measurement time [s]3 Ultra-High-Speed Satellite Communication Technology142　　　Journal of the National Institute of Information and Communications Technology Vol. 64 No. 2 (2017)