Scintillations of the GPS, GLONASS, and Galileo signals at equatorial latitude

Kurzfassung

Small scale ionospheric disturbances can lead to fluctuations of the received satellite signal, so-called signal scintillations. For global navigation satellite systems (GNSS) this reduces the positioning accuracy. Particular strong events can even lead to a loss of lock between satellite and receiver. All GNSS signals are affected by this phenomenon. The influence of the short scale disturbances on the different GNSS signals is expected to be different for each signal, since the signals are transmitted by different carrier frequencies and are constructed in different ways. In this paper, we compare the occurrence rate of signal scintillations between the different global navigation satellite systems and their different signal frequencies. In particular, we consider GPS L1, L2, and L5, GLONASS L1 and L2, and Galileo E1 and E5a. This analysis uses data from a high-rate GNSS station of the German Aerospace Center (DLR) placed in Bahir Dar, Ethiopia at 11°36′ N 37°23′ E. The station collects 50 Hz raw data from which the amplitude scintillation index S4 is calculated. The data has been collected for the whole year 2013. Since the number of strong scintillation events with S4 > 0.5 was smaller than expected, additionally weak scintillation events with S4 ≥ 0.25 are taken into account. An algorithm is used that provides a soft barrier for S4 ≥ 0.25. The resulting events are shown as daily and seasonal averages. Finally, the overall influence of short scale ionospheric disturbances in the form of signal scintillations on the GNSS signals is estimated.