Radar coverage assessment in nonstandard and ducting conditions: a geometrical optics approach

The authors set out to show that geometrical optics (GO) is particularly suitable for the real-time accurate computation of radar coverages in nonstandard atmospheres. A somewhat unusual GO differential system is used for predicting both ray paths and complex propagated fields within regular media. Optimal reductions of that formalism are obtained according to symmetry properties of the atmosphere. Reflections from the Earth and refractions through discontinuity layers are shown to admit simple analytical expressions in terms of the former system variables. An exact GO reciprocity property is then stated which enables the `two-way´ radar equation to be calculated in terms of existing radiated fields at the target location. Applications of the resulting computer code are presented highlighting the crucial ducting phenomena. The accuracy of this program is demonstrated through a comparison with previous results from a waveguide-mode scientific code. Computation times comply with shipboard operational requirements