Project outline: To derive ionospheric scintillation events from the S1 observable in GPS data derived from receivers that are spaced in the range 100 to 300 km To find correlations between scintillation events observed along ray paths from the same satellite by different receiver stations To use the azimuth and elevations of the ray paths (as seen from each receiver) along which scintillations were observed to derive estimates of the scintillation altitude To determine statistics of the mean altitude and altitude range of ionospheric scintillations