Precise Orbitography: A Foundation for EGNOS Performance
Berenguer, X.¹; Alcantarilla Medina, I.²; Chambre, E.¹; Ventura Traveset, J.³; Charlot, B.^1
1Thales Alenia Space; ²Groupo de Mechanica del Vuelo; ³European Space Agency

The EGNOS first release has been developed in Europe to provide GPS and GLONASS regional augmentation services to aviation, maritime and land users. EGNOS is a major element of the European Satellite Navigation Program, which is jointly being implemented by the Commission of the European Union, the European Space Agency (ESA) and EUROCONTROL. EGNOS is currently in operations (Initial Operational Phase) providing excellent results.

The EGNOS system, as the other Satellite Based Augmentation Systems, relies on the broadcast of correction and integrity information in the pseudo-range domain, which are then used to provide a solution in the position domain service.

This paper will focus on the EGNOS orbit module, and more specifically, on its associated algorithmic and performances, which have been recently further optimised. The paper will show that EGNOS GPS orbitography accuracies obtained are in the state of the art, when compared to other advanced techniques (e.g. as used by IGS).

The major results achieved since EGNOS System performances qualification will be addressed in details, addressing the identification and explanation of the improvements and tuning in the orbitography module, their benefit in terms of orbito/synchro performances and their positive consequences on the system performances.