Attenuation and cross-polarization measurements at 20 GHz using the ATS-6 satellite with simultaneous radar observations

Measurements of cross polarization using the 20-GHz beacon on the NASA-ATS6 satellite as received at a groundstation on Oxenhope Moor, Yorkshire, U. K. are reported. A co-sited range-gated radar was used to locate hydrometeors causing cross polarization. High cross polarization was frequently measured with little rainfall on the satellite radio path. Radar evidence shows that such "anomalous" cross polarization is associated with high-altitude particles well above the radar bright band. A pronounced correlation between atmospheric electricity, as measured with a point-discharge current probe and cross polarization is reported. In addition, abrupt changes in cross polarization were seen, coincident with lightning strokes. These results are interpreted in terms of scattering from ice needles lying in the horizontal plane and suffering orientation under the influence of static electric fields.