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Publications (1)0 Total impact

  • G. Bethscheider, J. Giannandrea, W. Schafer
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    ABSTRACT: Summary form only given. Wideband spread spectrum-coded signals are routinely used for satellite tracking and positioning purposes. These signals are transmitted using very low power levels simultaneously to the main digital or analogue direct-TV signal without any interference. The round-trip time-delay is measured, which provides the range at precisions of better than 5 cm. The line-of-sight velocity is determined at the same time with accuracies of better than 0.1 mm/sec. These ranging-signals have been received with independent time-receivers located in the footprint area of the satellite. The locally re-generated spread-spectrum symbol-rate stabilizes a low-phase-noise crystal oscillator, whose frequency is corrected for the Doppler shift induced by the satellite's relative movement. Orbital information and measured velocity is continuously broadcast from the ranging site to the user with minimum time delay in the form of user data modulating the spread-spectrum signal. Frequency and time-transfer accuracies achieved so far are presented. The system shows a potential frequency transfer accuracy compatible with good H-maser clocks for integration times of about one day and more. Further enhancements to the system are investigated to provide a reliable, highly accurate frequency and time reference
    European Frequency and Time Forum, 1996. EFTF 96., Tenth (IEE Conf. Publ. 418); 04/1996