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periments. Mirai is shown in Fig. 1.3WINDS-compatible earth station3.1WINDS-compatible marine-based earth statione appearance and specications of the station in-stalled on the Mirai are shown in Fig. 2 and Table 1, re-spectively. e station is equipped with an antenna system capable of acquiring and tracking satellites automatically and establishing communication lines even when the Mirai is moving. When set in regenerative mode, the WINDS station is able to establish communication lines capable of transmitting data at a maximum rate of 24 Mbps [4]. e station antenna estimates WINDS’ position based on the station’s current location and the strength of beacon signals received from WINDS and automatically acquires and tracks the satellite. e same antenna system has demon-strated the ability to track the satellite and establish com-munication lines when installed on a compact vehicle traveling at 100 km/h [5]. is satellite tracking antenna system is outlined below.When in search mode, the satellite tracking antenna system estimates the station’s position by receiving GPS signals and detects the strength of beacon signals from the satellite to acquire WINDS. Aer the satellite is acquired, the antenna system switches to beacon tracking mode, which enables it to implement monopulse satellite tracking and establish communication lines while a vehicle is mov-ing. If the antenna system is in beacon tracking mode and the reception of beacon signals is interrupted while the communication lines are in operation, it switches to a gyro holding mode, enabling it to re-estimate its current loca-tion and attitude using GPS signals. is process enables the antenna to reorient itself toward the satellite. If the beacon signal is not detected aer more than 60 seconds, the antenna system switches back to satellite search mode to re-acquire the satellite using open-loop pointing. ese satellite acquisition and tracking processes are shown in Fig. 3.3.251M-VSATWe used the 51M-VSAT at the NICT Kashima Space Technology Center (Kashima City, Ibaraki Prefecture) as AntennaCassegrain antenna(φ0.65 m)FrequencyTX: 27.5 – 28.6 GHzRX: 17.7 – 18.8 GHzPolarized waveLinearly polarizedAntenna gainTX: 42.5 dBiRX: 38.0 dBiOutput power20 WG/T13.5 dB/KData rateTX: 1.5/6/24 MbpsRX: 155 MbpsTabT1Specifications of the earth station on board vessel for WINDSFiF2External view of the earth station on board vessel for WINDSFiF3　Process of acquisition and trackingSearching Beacon TrackingBeacon lock Time Out Lost beacon lock Beacon lock Gyro Holding FiF1　External view of research vessel “Mirai”3 Ultra-High-Speed Satellite Communication Technology152　　　Journal of the National Institute of Information and Communications Technology Vol. 64 No. 2 (2017)