Spread Spectrum Time Transfer Experiment via INTELSAT

Abstract

Abstract : A two-way time synchronization experiment was performed in July 1983, between Washington, D.C. and Oberpfaffenhofen, Federal Republic of Germany. The experiment used the 14/11-GHz transponders on the INTELSAT V Atlantic spacecraft. The MITRED (Microwave Time and Ranging Experiment) modem designed, developed, and constructed at the Technical University of Berlin was employed. The experiment was jointly conducted by COMSAT Laboratories and the Institute for Nachrichtentechnik, DFVLR, Oberpfaffenhofen, FRG, in cooperation with the United States Naval Observatory and the Institut fur Luft- und Raumfahrt, TU Berlin. The spread spectrum signal occupied a bandwidth of 4 MHz and used the power normally required by a single-voice carrier. The ground stations involved had parabolic dishes of 2.4 m (G/T = 20 dB/K) and 4.5 m (G/T = 26 dB/K). In the 4-MHz occupied bandwidth, the carrier-to-noise ratio was -11 dB. At this power level, the time transfer performance had rms-standard deviations of better than 1 ns. The experimental results confirm that an international time transfer and clock synchronization network using communications satellites is economically viable when using a spread spectrum transmission format. (Author)