A NEW VHF-INTERFEROMETER WITH THREE STEERABLE HIGH-GAIN-ANTENNAS FOR SATELLITE-TRACKING

Abstract

The German-Central-Ground-Station near Weilheim, Bavaria, called Z-DBS, operates now on VHF-Telemetry and Telecommand. Its monopulse-autotrack-subsystem measures one way doppler datas and medium-precise (~0,25° RMS) direction angular (AZ,EL) datas. For precise orbital tracking the station will now be completed by a VHF-Interferometer with three steerable high-gain-antennas, using the angular information of the existing system for initial acquisition and ambiguity resolution. Such a system is applicable to track most near-earth-satellites in orbit without needing a global network even with a relatively low percentage of contact time because of its large angular- and distance-coverage from one topos. The interferometer, now under construction, will be ready for operation at the end of 1973. The present paper gives a brief description of the parameter requirements, the system itself and the methods used to overcome the very high technical difficulties. The total residual direction error is predicted not to exceed (10÷15)”, including nearby ground reflexions but excluding residual athmospheric propagation effects. High side-lobe-suppression-antennas with extremly stable phase characteristics as well as a 3-channel-piloting-receiver-system are used to make the antenna’s difference-phase errors small enough and to eliminate phase changes throughout long cables and receivers. A computer operates the whole system to a high degree of automacy and evaluates and smoothes the direction datas.