Project Echo: Antenna Steering System

Although communications antennas could be slaved to optical or radar trackers at each antenna site, the use of basic orbital information to generate antenna steering instructions is expected to be more economical when many antennas and sites are served. The latter method was used in Project Echo and employed the following steps: 1. determine satellite positions by accurate radio observations and, from these, calculate the basic satellite orbital elements; 2. use these elements to calculate future satellite positions; 3. from these positions, compute pointing angles for the antennas. In the Echo experiment, these functions were performed by the Minitrack satellite tracking network and the Goddard Space Flight Computation Center, which are facilities of the National Aeronautics and Space Administration. The predicted angles were transmitted by teletypewriter from the computer at Washington to the Pell Telephone Laboratories antennas on Crawford Hill at Holmdel, New Jersey. The first portion of this paper discusses system design problems concerning the transmission of pointing information from computer to antenna site, and conversion of these data into servo-actuating signals that move the antennas to the predicted angles at the desired time. The second portion describes how 1207