Performance Assessment of Time Difference Between EGNOS-Network-Time and UTC

J. Delporte, F. Mercier, J. Maréchal, M. Jeannot, J-Y. Richard, P. Uhrich

Abstract:	The European Satellite Based Augmentation System EGNOS (for European Geostationary Navigation Overlay Service) is now operated and provides in its navigation message the time difference between EGNOS Network Time (ENT) and UTC to users. For this purpose one EGNOS Earth station has been installed in Paris Observatory (OP) providing a physical link to UTC(OP). Applying EGNOS corrections on GPS measurements provides a precise time and navigation solution referenced to EGNOS Network Time. Assessment of the time difference between ENT and UTC is therefore a key issue for time users. First the paper details the time aspects of EGNOS and describes the connection of ENT to UTC(OP). EGNOS system time requirements are also reminded. Then the two methods of performance assessment are described. The first method consists in estimation at user level, in locations where EGNOS corrections are either valid or not : - for a user in a location where EGNOS corrections are valid, an estimate of the difference between his receiver time and ENT can be produced using GPS measurements and EGNOS corrections. If the receiver clock is connected to a UTC(k), an estimation of ENT-UTC(k) is obtained. UTC(OP) is used in this paper. - for a receiver outside EGNOS coverage, the use of IGS precise ephemeris and clocks allows a time transfer between the receiver clock and EGNOS time. The second method is based on the time difference between ENT and UTC broadcast in EGNOS SIS (SBAS Message #12) validated using internal delays of EGNOS Earth station located in Paris Observatory. The results of the two methods will be compared and checked vis-à-vis EGNOS system requirements.
Published in:	Proceedings of the 19th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2006) September 26 - 29, 2006 Fort Worth Convention Center Fort Worth, TX
Pages:	913 - 920
Cite this article:	Delporte, J., Mercier, F., Maréchal, J., Jeannot, M., Richard, J-Y., Uhrich, P., "Performance Assessment of Time Difference Between EGNOS-Network-Time and UTC," Proceedings of the 19th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2006), Fort Worth, TX, September 2006, pp. 913-920.
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