Impact of Ionospheric Scintillations on SBAS Performance

S. Skone and K. Knudsen

Abstract:	For reliable operation of Satellite-Based Augmentation Systems (SBAS), GPS observations must be available continuously in the reference network, and at remote users' receivers. Loss of signal availability, leading to a degradation of SBAS performance, can occur during periods of ionospheric scintillations - a significant concern during the current solar maximum. Scintillation effects arise from small-scale irregularities in electron density, which are most commonly observed in the high latitude auroral region and the low latitude equatorial anomaly region. The auroral region expands equatorward during intense geomagnetic storms, and scintillation effects may be observed in the Southern United States and Europe. The impact of equatorial scintillation is expected to peak during the years of solar maximum, while high latitude storm activity is expected to peak in the following years (2001-2003). SBAS are currently being implemented in Canada (CWAAS), the United States (WAAS), Europe (EGNOS), and Asia (MSAS) - regions which may all be affected, to some extent, by the presence of scintillations. Future extension of SBAS also includes equatorial regions such as South America. In this paper, the impact of scintillation effects on receiver tracking performance is assessed using dual frequency GPS observations from reference networks in Scandinavia and Brazil. These networks provide excellent coverage of the auroral and equatorial regions. The impact of scintillation activity is quantified by the loss of phase and code observations, the number of satellite observations lost simultaneously, and the duration and spatial extent of degraded receiver tracking performance within the networks. Results are interpreted with respect to availability of network observations, particularly in terms of reliable ionosphere modeling. A comparison of receiver tracking technologies is also conducted, using both codeless and semicodeless GPS receivers. The tracking capabilities of three survey-grade receivers are compared under identical scintillation conditions, and it is demonstrated that tracking performance can vary significantly between receivers - an important issue in choosing reliable reference network receivers.
Published in:	Proceedings of the 13th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2000) September 19 - 22, 2000 Salt Palace Convention Center Salt Lake City, UT
Pages:	284 - 293
Cite this article:	Skone, S., Knudsen, K., "Impact of Ionospheric Scintillations on SBAS Performance," Proceedings of the 13th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2000), Salt Lake City, UT, September 2000, pp. 284-293.
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