Evaluation of amplitude and phase scintillation impact on GPS and Galileo frequencies 

<p>Global Navigation Satellite Systems (GNSS) has been widely used in aviation applications, nonetheless its accuracy and reliability are degraded under ionospheric scintillation. This effect on the radio wave signals causes a rapid fluctuation on both amplitude and phase of the signals, which may even lead to loss of lock in the worst case. The (Ground Based Augmentation Systems) GBAS based on GNSS signals is used for positioning improvement of aircraft landing. For safety-of-life applications, augmentation systems are necessary once reliability under all conditions is of great importance. Therefore, the evaluation of GNSS performance under amplitude and phase ionospheric scintillation is an important task when introducing a new safety-of-life technology such as GBAS. In this context, we present a quantitative analysis of the ionospheric amplitude and phase scintillation impact on the GPS and Galileo frequencies. Analysis considered S<sub>4</sub> and σ_moraeφ60 behavior for the same frequencies between both systems (L1 = E1 and L5 = E5a signals). The data used in this study were measured by a station located in a region characterized by the occurrence of strong scintillations, station SJCU (23.1°S, 45.8°W). The analyzed data were collected from November 12 to December 12, 2014, a period with moderate to strong solar activity. S4 and σ<sub>φ </sub>indices were estimated for satellites with elevation angle higher than 20° and indices values classified above 0.2 and 0.08, respectively. Considering GPS, amplitude and phase scintillation, the L5 signal had the greatest ionospheric impact in 91.7% and 98.4% of the epochs, respectively. Considering Galileo, for amplitude and phase scintillation, the E5a signal had the greatest ionospheric impact in 96.4% and 99.4% of the epochs, respectively. Those results indicate that lower frequencies are most affected under ionospheric scintillation. Similar behavior could be observed considering the same frequencies with GPS and Galileo, specially taking into account phase scintillation for L5 and E5 frequencies.</p>