AN IMPROVED METHOD OF SYNTHESIZING GROUND BACKSCATTER IONOGRAMS FOR SPHERICAL IONOSPHERES

Synthesis of ground backscatter ionograms is a useful technique for st udying the structure of the ionosphere. By synthesizing backscatter io nograms from a known ionosphere, knowledge can he obtained on how vari ations in the ionosphere affect the shape of a backscatter ionogram. A method allowing the rapid synthesis of ground backscatter ionograms i s presented. The vertical ionospheric profile is represented by a seri es of smoothly joined quasi-parabolic segments which can accurately re produce both measured and model profiles. The ionosphere is, however, restricted to being spherically symmetric. The synthesis includes corr ections for geometrical and time delay focusing. The speed of the tech nique is valuable when ionospheric state is to be determined by seekin g a match between measured and synthesized backscatter ionograms. The restriction of the synthesis to spherically symmetric ionospheres mean s that the best choice can only be made from this class. Residual diff erences can be a useful indication of the significance of departures f rom spherical symmetry. The calculations involved in the synthesis are closely related to those necessary to establish coordinate registrati on in the location of targets for over-the-horizon radar.