Evidences of ionospheric scintillation effects over GPS loss of lock

In collaboration with Cornell University, ionospheric scintillation monitors (SCINTMON) were installed at many sites over Brazil, to study the degradation of GPS signals due to ionospherics scintillations. These monitors are GEC-Plessey GPS development cards modified to sample the wide band power of the GPS signal at a high rate (50 samples/sec). To quantify the magnitude of the ionospheric scintillations, the S4 index, that is the standard deviation of the GPS signal amplitude relative to its average for each minute, was used. This paper presents the correlations between the GPS signal scintillations, that occur during ionospheric irregularities, with signal loss of lock with consequent decrease of available satellites and degradation (increase) in the GDOP Geometric Dilution of Precision). Data from Cachoeira Paulista (22.57o S, 45.01o W, dip latitude 18.12o S) and São José dos Campos (23.07o S, 45.86o W, dip latitude 18.01o S) during periods of average and high solar activity were used.