Reduction method of pointing error of El/AZ mount for maritime satellite communications

Development of small marine antennas has a very important role in the maritime satellite communications with small ships, especially for Japan which has a relatively large number of small fisherboats. As the satellites become larger in size in the future, the shipborne antennas will tend to become smaller. We propose a control method for the antenna mount against ship motions to assure pointing the communication satellite. The two-axis EL/AZ mount has a light weight and a small size, which gives rise to a large pointing error when the satellite is near the zenith or when the AZ axis is near the control limit for avoiding twisting the cables. We have developed an algorithm to reduce the pointing errors within the pitching amplitudes of the ship. The principle and the experimental results of this system are described.