Integrity Investigations within the European Galileo System Test Bed (GSTB)

W. Werner, N. Lemke, I. Deuster, U. Rossbach

Abstract:	The European Galileo System Test Bed V1 (GSTB-V1) main goal is to reduce major risks inherent with Galileo system design activities and algorithm developments. One important issue hereby is to investigate the Galileo system with respect to achievable performances and to select the final set of orbit determination, time synchronisation (OD&TS) and integrity algorithms out of a set of candidate system algorithms. One of the major aspects is focussed on system integrity analyses. GSTB makes use of GPS data monitored by a worldwide network of ground stations. These data are gathered at the GSTB processing centre (GPC) and fed into a chain of processing facilities, providing OD&TS algorithms as well as signal-in-space accuracy (SISA) and integrity algorithms. Analysis results will be extrapolated to Galileo signal structures and frequencies. The GSTB element that provides the capability to investigate integrity issues is called Experimental Integrity Processing Facility (E-IPF). It is designed to allow for flexible data evaluation and experimentations. Integrity performances will be estimated based on the OD&TS computation results and "truth references" (precise orbits and clocks) taken from the International GPS Service (IGS). Two different possibilities are foreseen how the E-IPF can be exploited: On the one hand, there is a routine data processing that works in a (more or less) continuous way. The raw measurement data coming from the ground stations network are gathered at the Data Server Facility (DSF) and forwarded together with SISA data to E-IPF for this standard data processing. The produced data are integrity flags, false alarm and missed-detection rates and several other types of statistics and useful integrity-related information. All these data will be made freely available through the worldwide web (WWW). The second way to use the E-IPF is through specialised integrity experimentation. Here the E-IPF can be configured in a very flexible way to output relevant integrity-related diagnostic data and statistics. This way of usage, however, requires expert knowledge and is restricted to authorised users only. The first part of the paper presents the context and overall design of the E-IPF together with the core products that are generated by the E-IPF. There will be five main components in the E-IPF: interface server, processing kernel, configuration tool, monitoring agent and long-term statistics generator. Each of these components, their functionalities and interrelations are described in detail. The second part of the paper describes the implemented Galileo baseline algorithms as well as several alternate candidate core integrity algorithms and the possibilities for integrity testcase experimenting. Furthermore, simulation and manipulation algorithms that are used to contaminate the raw measurement data with different types of feared events as well as the necessary analysing algorithms are presented. As the operational phase of the GSTB processing centre and the routine data processing is about starting, some early results are also provided.
Published in:	Proceedings of the 16th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS/GNSS 2003) September 9 - 12, 2003 Oregon Convention Center Portland, OR
Pages:	2478 - 2486
Cite this article:	Werner, W., Lemke, N., Deuster, I., Rossbach, U., "Integrity Investigations within the European Galileo System Test Bed (GSTB)," Proceedings of the 16th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS/GNSS 2003), Portland, OR, September 2003, pp. 2478-2486.
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