Communication Satellite Control Systems

During the last 12 years, global communication via earth satellites has grown from an experimental status to fully operational international and domestic systems. These satellites have utilized spin stabilization for the most part because of its inherent simplicity and high reliability. Moreover, the evolution in spin stabilization technology has kept pace with increasingly stringent payload pointing requirements that have arisen due to use of higher frequencies and spot beams for selected area coverage. This paper deals with attitude control technology as it applies to typical communications satellites. The basic stabilization problem is stated in terms of the system requirements and perturbations such as environmental disturbances and the effects of internal fuel slosh. Next, design practices and hardware technology are reviewed for the current generation of dual-spin satellites. Reaction jets, sensors, nutation dampers, and despin bearing assemblies are the principal hardware elements considered. Two types of control system configuration are discussed: one using onboard pulse data and one deriving a continuous error signal from a ground beacon. Finally, some future trends in satellite attitude control technology are discussed.