Temporal Decorrelation of GPS Satellite Signals due to Multiple Scattering from Ionospheric Irregularities

and continues to vary with the strength of the ionospheric perturbation once when the S4 index has saturated. In this paper we characterize the temporal decorrelation of the GPS satellite signals using 20 Hz observations collected at Ascension Island (7.96oS, 14.41oW, dip latitude 12.4oS) on 5-19 March 2002, during solar maximum conditions. We explore the relationships between the ionospheric scintillation parameters, loss of lock, and signal reacquisition time and provide empirical fits to the probability of losing lock for use in modeling and simulation studies. Our results suggest that rate of signal fluctuation, in addition to the depth of signal fading, should be considered when modeling GPS receiver performance in the presence of scintillation. We observed that the probability of loss of lock and likelihood of extended signal reacquisition times depend on the velocity of satellite motion with respect to the magnetic field and plasma drift, which are relatively predictable a priori in the equatorial region.