Ice depolarization of the COMSTAR beacon at 28.56 GHz during low fades and correlation with radar backscatter

Radar correlation with significant ice depolarization events accompanied by low copolarization fades of the 28.56-GHz COMSTAR beacon signal are described for an experimental program at Wallops Island, VA. Using a Faraday switch at the front end of the receiver, the copolarization and cross-polarization levels of the 28.56-GHz beacon signal are sequentially monitored. A nearby high resolution -band radar pointing along the Earth-satellite path monitors the simultaneous ice and rain reflectivity. Excellent correlation is noted between the cross-polarization events and relatively large and extended ice reflectivities along a segment of the Earth-satellite path at altitudes near and above the 0°C isotherm. The radar and receiver data strongly suggest the cross-polarization mechanism is due to a hailshaft which intersects the path at altitudes well below the 0° isotherm. Since the intervening ice results in a cross-polarization signal which either adds or subtracts to the cross-polarization antenna residual, a method is described to remove the residual from the resultant measured cross-polarization level, without employing a phase measurement. Cumulative, month-of-year and time-of-day statistics associated with the depolarization signals are established.