Digital Equipment for the Antenna Pointing System

The primary function of the digital equipment in the Telstar antenna pointing system 1 is to generate pointing information for the horn-reflector antenna. The performance of this function requires the prediction of the ephemeris from previously acquired information on the satellite orbit. Together with the precision tracker 2 and the horn antenna, 3 the digital equipment provides means for the acquisition, recording, and storage of the track information in each pass. These data are used to periodically up-date the parameters which describe the satellite's orbit. These updated parameters are the basis for the generation of the pointing instructions which are stored and used to control the horn antenna and precision tracker during future passes. During a pass the pointing instructions are synchronized with real time, interpolated to provide a smooth flow of data and then compared with the actual antenna postion. To insure accuracy in the conversion of the digital pointing instructions to the analog inputs required by the antenna servo, 4 the input comparison is performed digitally. The conversion to analog voltages is performed on the difference, or error, signals for which the accuracy requirements are not extreme. In addition, the digital equipment performs a variety of other functions which will be described in this paper. In Section II a general description of the seven functional units mak1223