Ionospheric Scintillation analysis using ROT and ROTI for Slip Cycle Detection

Ionospheric scintillation is one of the most challenging problems in satellite navigation systems. This phenomenon appears when a signal passes through ionospheric irregularities. These irregularities occur due to rapid changes in ion density of ionosphere, and this tends to change in the refraction index. Depending on their size, they can produce diffractive effects that affect amplitude and phase of the signal. The amplitude and phase scintillations can lead slip cycles in carrier phase measurement and loss of signal lock during extreme scintillation. The presence of slip cycle in carrier phase measurements prevents it to be directly used for ionospheric total electron content (TEC) estimation. For the study of scintillation events S4 index (normalized standard deviation of signal strength) and $\sigma_{\phi}$ index (standard deviation of signal phase) were being used, but recently Rate of TEC index (ROTI) based method has been found more suitable for detection and analysis of scintillation events. In this paper, scintillation events have been analyzed by Rate of TEC (ROT) and ROTI and compared for suitability of slip cycle event detection.