Ionospheric Storms of Solar Cycle 24 and their Impact on the WAAS Ionospheric Threat Model

Lawrence Sparks, Eric Altshuler

Abstract:	Disturbances in the ionosphere can hinder the propagation of radio signals through the earth’s atmosphere, thereby becoming major sources of error for position estimates determined from measurements of signals emitted by Global Positioning System (GPS) satellites. The Wide Area Augmentation System (WAAS) broadcasts parameters that allow a GPS user navigating over North America to compute corrections to position estimates and to bound the positioning errors that arise from ionospheric delay. Contributing the dominant term to the broadcast grid ionospheric vertical error (GIVE), the WAAS ionospheric threat model protects the user from threats posed by undersampled ionospheric irregularities. The threat model currently fielded has been derived entirely from historical observations recorded during solar cycle 23 when the WAAS receiver network was comprised of only twenty-five stations. The next upgrade of the WAAS ionospheric threat model will incorporate observations from solar cycle 24, recorded at all thirty-eight stations in the current receiver network. This paper examines the impact that solar cycle 24 storms are likely to have on both the threat model and on the consequent availability of the system, and it proposes a means of improving WAAS availability without sacrificing system integrity.
Published in:	Proceedings of the 29th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2016) September 12 - 16, 2016 Oregon Convention Center Portland, Oregon
Pages:	682 - 690
Cite this article:	Sparks, Lawrence, Altshuler, Eric, "Ionospheric Storms of Solar Cycle 24 and their Impact on the WAAS Ionospheric Threat Model," Proceedings of the 29th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2016), Portland, Oregon, September 2016, pp. 682-690. https://doi.org/10.33012/2016.14850
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