Scintillation Characteristics Across the GPS Frequency Band

Charles S. Carrano, Keith M. Groves, William J. McNeil, and Patricia H. Doherty

Abstract: We investigate the characteristics of ionospheric scintillation across the entire GPS frequency band spanning the L5–L1 carrier signals (1176 MHz–1575 MHz). Of particular interest is the intensity correlation between carrier pairs, since this dictates the extent to which frequency diversity may be leveraged to mitigate scintillation impacts on navigation accuracy. Since only a few satellites currently broadcast the L2C and L5 signals, a limited number of scintillation field measurements have been collected to date. We show recent scintillations observations on L2C in Brazil collected in April 2012. Since current solar conditions are less disturbed than during the previous two solar maximum periods, however, it is not possible to explore the full range of scintillation conditions with current measurements alone. Therefore, we have developed a high-fidelity simulation technique to infer the complex (amplitude and phase) fluctuations of the L2 and L5 carrier signals from complex fluctuations of the L1 carrier signal recorded during the previous solar maximum. We compare this technique with two stochastic approaches which use the S4 index, rather than the raw complex data, as input. After demonstrating that the three techniques yield consistent results, we apply the simplest of these approaches to a database of L1 S4 observations from the previous solar maximum to determine the climatology of intensity fluctuations on the L2 and L5 carriers and the cross-correlation of intensity fluctuations between them. As expected, we find a marked decrease in correlation between the GPS carrier signals as the scintillation strength increases. This suggests engineering approaches which utilize frequency diversity may be able to partially mitigate the effects of scintillation when it is most needed, e.g. when the scintillation is strong. Moreover, we find a simple relationship between the intensity correlations and the L1 S4 index which holds irrespective of the propagation geometry. This relationship provides a simple way to predict the intensity correlations for use in scintillation trade studies.
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: 1972 - 1989
Cite this article: Carrano, Charles S., Groves, Keith M., McNeil, William J., Doherty, Patricia H., "Scintillation Characteristics Across the GPS Frequency Band," Proceedings of the 25th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2012), Nashville, TN, September 2012, pp. 1972-1989.
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