GNSS Survey - Signal Quality Assessment of the Latest GNSS Satellites

Steffen Thoelert, Johann Furthner, Michael Meurer

Abstract:	2012 was an amazing year in the field of global navigation satellite systems. A significant number of major milestones were reached by the different navigation and augmentation systems GPS, Galileo, GLONASS, COMPASS, EGNOS, GAGAN, etc. by bringing new satellites and satellite generations into orbit. Especially with GLONASS-K2 and the second dual satellite launch of Galileo the highlights of this year were announced. But the launches were delayed. Thus measurement results only from Galileo and COMPASS are presented within this paper. The third and fourth In-Orbit-Validation (IOV) satellites of the European Navigation System Galileo launched in October 2012 allow tests of the real performance of the Galileo system on ground for the first time. Based on ground measurements each of the above mentioned satellite was certainly proved extensively but physical stress during the launch and the different environmental conditions in space may lead to several imperfections within the signal transmission. Therefore and, especially, since the complexity of the satellites and also the requirements for a precise and robust navigation are constantly rising, all of the newly available signals of the existing or emerging navigation satellite systems have to be analysed in detail in order to characterize their performance and imperfections as well as to predict possible consequences for user receivers. Since the signals are well below the noise floor, the authors use a specifically developed GNSS monitoring facility in order to characterize the GNSS signals. The core element of this monitoring facility is a 30m high-gain antenna at DLR / Weilheim which raises the GNSS signals well above the noise floor allowing detailed analysis. Doing this analysis differences in the signal quality were found in the different generations of the Chinese navigation satellite system COMPASS, which show influences on the navigation performance. The paper shows an overview of new navigation satellites in orbit. Last updates of the modernized DLR GNSS monitoring facility will be introduced especially the online calibration system. For selected satellites a first signal analysis is performed revealing important characteristics of these signals. The data acquisition of the presented space vehicles was performed shortly after the start of their signal transmission to get a first hint about the quality and behaviour of the satellites. For more detailed analysis the measurements should repeat after the satellites become operational. Then the acquired high gain antenna raw data in combination with a precise calibration could be used for a wider range of analyses i.e. signal power, spectra, constellation diagrams, sample analysis, correlation functions and codes to detect anomalies and assess the signal quality and consequently the impact at the user performance.
Published in:	Proceedings of the 2013 International Technical Meeting of The Institute of Navigation January 29 - 27, 2013 Catamaran Resort Hotel San Diego, California
Pages:	608 - 615
Cite this article:	Thoelert, Steffen, Furthner, Johann, Meurer, Michael, "GNSS Survey - Signal Quality Assessment of the Latest GNSS Satellites," Proceedings of the 2013 International Technical Meeting of The Institute of Navigation, San Diego, California, January 2013, pp. 608-615.
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