Development and Early Results of a GALILEO UERE/UERRE Monitoring Facility

W. Werner, U. Rossbach, M. Eleuteri, D. Cretoni

Abstract:	Since satellite navigation systems exist, there is the question with regard to their performances in terms of accuracy, availability, continuity and within the last years also in terms of integrity. Considering the accuracy error budget many models have been developed by scientists, institutions or companies over the last thirty years. These models try to characterize the error on the satellite signals in a statistical way to be able to take them into account in an optimal tuning of parameters for position, velocity and time solutions. Due to the GPS pioneering role in satellite navigation systems, the models have been used and validated for GPS in most of the cases. The future European satellite navigation system Galileo is now on the horizon. Hence, performance verification based on real Galileo signal measurements now becomes more and more important for Galileo. Within the ESA GSTB-V1 project Galileo end-to-end performances have been investigated for the first time with real Galileo algorithms, but based on GPS signals. Within GSTB-V2 the signals of the first Galileo test satellites have been analyzed. With Galileo aiming at very high performance standards, it becomes important that the actually reached performance is verified and checked independently. One of the performance parameters of a satellite navigation system is accuracy. Although one of the most important aspects, the User Equivalent Range Errors (UERE) and User Equivalent Range Rate Errors (UERRE) from the user point of view so far have not been assessed yet. Therefore, a UERE/UERRE Monitoring Facility (UMF) is being developed. The objective of the UMF is the determination of the UERE/UERRE budget on Galileo signals as well as the characterization and verification of Galileo receivers. The UMF is able to separate the major UERE/UERRE error components and compute relevant statistics on them. For this purpose the UMF consists of a control computer and several environmental sensors, like a meteorological sensor, a Integrated Water Vapor (IWV) radiometer and a GPS reference receiver. Furthermore, it makes use of a high-quality rubidium frequency standard, a spectrum analyzer and, of course of the Galileo receivers. In addition to the environmental sensors reference data, such as precise orbit and clock data, are needed that come from external sources. The error components that can be determined are satellite orbit and clock error, tropospheric and ionospheric residual errors, multipath, interference effects and measurement noise. All these error components can be computed per frequency E1, E5, E6 and per service Open Service (OS), for dual or single frequency users, as well as for the Safety-of-Life service (SoL). An Early Version (EV) of the UMF that is capable of analyzing data of GIOVE-B signals has already been developed and first results are available. This paper describes the context, purpose, functionality, architecture and algorithms of the UMF.
Published in:	Proceedings of the 22nd International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2009) September 22 - 25, 2009 Savannah International Convention Center Savannah, GA
Pages:	2990 - 2995
Cite this article:	Werner, W., Rossbach, U., Eleuteri, M., Cretoni, D., "Development and Early Results of a GALILEO UERE/UERRE Monitoring Facility," Proceedings of the 22nd International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2009), Savannah, GA, September 2009, pp. 2990-2995.
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