Ionospheric Scintillation Predictions for the Geostationary Satellites GOES & ATS-F

Abstract

Maps of scintillation indexes over the region of the earth viewed by a geostationary satellite at 100^o W longitude were produced using the SRI global model for scintillation [Fremouw, E. J. & Rino, C. L., <i>Radio- Sci., </i> 8 (1973), 213]. These maps were calculated for several times of the day, for the solstitial and equinoxial variations, and for sunspot numbers corresponding to high, medium and low solar active periods. The contours represent a convolution of the elevation angle, position, and diurnal variations. The equatorial region shows the most severe scintillation effects in the region of ± 200 from the geomagnetic equator. Strong effects are also shown for the auroral zone, while midlatitudes are nearly free from scintillation activity. The worst case conditions occur in the equatorial region for sunspot number 200 during the equinoctial periods, and for the regions of the earth having local time near midnight. Under these conditions, the scintillation indexes will be saturated (i. e., approximately 1). These maps should be useful in determining the deployment of buoys and other surface stations for use with the GOES (Geostationary Operational Environmental Satellite) data collection and relay system. The method is also applied to the radio beacon frequencies .10 and 360 MHz of ATS-F to be launched in 1974 for communication experiments to be conducted in India. The predictions indicate that scintillation activity will be large at times even during periods of low solar activity particularly near midnight, and during equinoxes.