Potentials for GNSS Signal Enhancements - An Assessment of the Impact of Satellite Imperfections on the Navigation Performance of Todays and Future GNSS

M. Meurer, S. Thoelert, S. Erker, O. Montenbruck

Abstract:	The launch of GPS space vehicle 49, at the latest, provided clear evidence to the GNSS community that satellite imperfections are very diverse and do not necessary match with the models used on ground for system development. Non-linearities, frequency selectivity, satellite inherent multipath and even elevation dependent signal distortions have to be considered – only to mention some of the drawbacks seen on today’s satellites. Those imperfections are quite common and can be found on a multitude of GNSS satellites. It is the aim of this paper to learn from the performance of the signal transmission payloads of the GNSS satellites already in orbit in order to better understand payload limitations and signal imperfections in real environments. It is the intention to characterize typical payload imperfections for using them in the context of receiver performance assessment and optimization as well as for the design of future GNSS signals. In the paper a methodology is derived for utilizing high gain antenna measurements for systematically characterizing satellite transmitter imperfections. It will be shown that hybrid impulse responses (HIR) are a suitable means for achieving that objective. Based on HIR, transfer functions of satellite transmitter frontends, chip shape deformations etc. are derived. Using the example of GPS SV49 the deformations caused by the well known satellite induced and elevation dependent multipath error are assessed. Using measurements for a full pass of that satellite over a DLR ground station and by employing the proposed methodology an accurate model of the multipath error is derived. Doing so several uncertainties in literature about the nature of this imperfection are resolved.
Published in:	Proceedings of the 23rd International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2010) September 21 - 24, 2010 Oregon Convention Center, Portland, Oregon Portland, OR
Pages:	924 - 934
Cite this article:	Meurer, M., Thoelert, S., Erker, S., Montenbruck, O., "Potentials for GNSS Signal Enhancements - An Assessment of the Impact of Satellite Imperfections on the Navigation Performance of Todays and Future GNSS," Proceedings of the 23rd International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2010), Portland, OR, September 2010, pp. 924-934.
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