The characteristics of advanced digital transmission systems were measured using newly developed small earth stations and a K-band (30/20 GHz) and C-band (6/4 GHz) communication satellite. Satellite link performance for data, facsimile, video and packet switching information transmission at bit rates ranging from 6.4 kbit/s to 6.3 Mbit/s have been confirmed, using a small K-band (30/20 GHz) earth station and a demand assignment time division multiple access (DA-TDMA) system. A low-capacity omni-use C-band (6/4 GHz) terminal experiment has verified a telephone channel transmission performance by spread-spectrum multiple access (SSMA). Single point to multipoint transmission characteristics of the 64 kbit/s data signals from the computer centre were tested using a receive-only 4 GHz earth terminal. Basic satellite link performance was confirmed under clear-sky conditions; however, evaluation of the satellite link is also described based on rain attenuation and sun-transit interference data. Precise satellite orbit and attitude keeping experiments were carried out to obtain precise satellite antenna pointing accuracy for development of K-band earth stations that do not require satellite tracking equipment. Precise station keeping accuracy of 0.02 degrees was obtained.