An Analysis of Measurement Derived Sea Clutter Simulations at Very Low Grazing Angles, in the Presence of Surface Based Ducting

Sea clutter can have significant performance impacts on shipboard radar systems, particularly against low flying targets. It is essential to the evaluation of shipboard radar system performance, for engineers to have available very accurate sea clutter simulation models, which include the effects of anomalous propagation, as well as rough surface scattering, on the clutter return. In at-sea-tests, sea clutter returns from long ranges have been measured which are larger than the current sea clutter models have predicted. Not only do such large undesirable returns interfere with detection performance, but the presence of strong surface based ducting can result in extended range clutter folding, which may limit the usefulness of clutter mitigation approaches. The importance of the key parameter, grazing angle, in the computation of sea clutter cannot be overstated. Within the horizon the grazing angle is well understood, beyond the horizon grazing angle is a topic of considerable discussion (D.E., Barrick, 1998). The sensitivity of the sea clutter reflectivity models to grazing angle, within the context of trans-horizon ducted propagation is the focus of the issue being raised by this paper. In addition to the trans-horizon grazing angle issue, the difficult decision of selecting the height at which the propagation factor is modeled, is also discussed.