| Résumé | Since July 1978, time comparisons between National Research Council of Canada and Paris Observatory, France, are regularly made via the geostationary telecommunication satellite "Symphonie". The experiment is planned to last at least two years. Until February 1979, the time comparisons were made daily, then twice a week.
A two-way technique is used between earth stations in Ottawa and Pleumeur-Bodou, on the 4-6 GHz channels. The link is complemented by passive television between earth stations and time laboratories.
The random uncertainty of the space link is of the order of 1-2 ns, but the overall random uncertainty is strongly increased by the television method and reaches 24 ns. The results still contain a constant error of the order of a few 0.1 PS, due to the lack of precise calibrations of instrumental delays ; the calibration methods are under study.
These time comparisons require a reasonable amount of work, compatible with routine operation. The work can still be reduced by various technical improvements which are in progress. The results appear especially fitted to detect rapidly frequency changes and such a 1 would be very useful between laboratories developing primary standards. |
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