New Birds in the Sky - Signal in Space (SIS) Analysis of New GNSS Satellites

Steffen Thoelert, Johann Furthner and Michael Meurer

Abstract:	In 2012 a number of major milestones were reached by different satellite navigation systems. New satellites of GPS, GLONASS, COMPASS and IRNSS systems are in space and can be used for navigation. Moreover, the first two In-Orbit-Validation (IOV) satellites of the European Navigation System Galileo were launched by end of 2011 and began transmitting signals on all three Galileo frequencies in parallel beginning of 2012. Although for most of the systems mentioned above the expected signals according to textbooks or ICDs are known, in reality due to imperfections several deviations can be seen. 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. The fully renewed and modernized DLR GNSS monitoring facility is introduced which now allows coherent capturing of two signals at a time. Doing so inter-frequency analysis or axial ratio behaviour of the transmitted satellite signals are possible. For selected satellites a detailed signal analysis is performed revealing important characteristics of these signals. The acquired high gain antenna raw data in combination with a precise calibration are used for a wide range of analyses i.e. signal power, spectra, constellation diagrams to detect anomalies and assess the signal quality. In addition the signal quality not only of selected new satellite will assessed but also the signal quality development over generations will discussed based on an example of the COMPASS/Beidou system. The paper ends with some conclusions and outlook for the next year.
Published in:	Proceedings of the 25th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2012) September 17 - 21, 2012 Nashville Convention Center, Nashville, Tennessee Nashville, TN
Pages:	3613 - 3619
Cite this article:	Thoelert, Steffen, Furthner, Johann, Meurer, Michael, "New Birds in the Sky - Signal in Space (SIS) Analysis of New GNSS Satellites," Proceedings of the 25th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2012), Nashville, TN, September 2012, pp. 3613-3619.
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