The on-orbit antenna pointing calibration of Milstar satellite gimbaled parabolic antennas

To minimize enemy jamming impacts and to maximize communications coverage of friendly forces, the modern military satellite communications systems require accurate determination of the antenna Earth coverage areas. Also, an accurate antenna pointing system is required to satisfy the link budget requirements on the edge of antenna coverage. The antenna pointing accuracy can be improved considerably by on-orbit calibration of the diurnal satellite antenna pointing misalignment error which arises from the combination of several error sources, such as structural thermal deformations, the attitude determination system, the antenna ground alignment procedure, and the antenna gimbal system. This paper describes how an approximately tenfold reduction in pointing error can be achieved from on-orbit antenna pointing calibration of the gimbaled antenna of the Milstar satellite. In addition, the paper describes the process that was implemented to achieve these results.