The development of a normalized radar cross section model for icebergs

Abstract

To reliably assess the detection performance of marine radars against iceberg targets a realistic model of the normalized radar cross section is required. Previous research indicates that the radar cross section of an iceberg is directly proportional to the area of an iceberg projected onto a plane normal to the radar beam and that aspect and overall shape are secondary factors. Physical descriptions of the iceberg surface indicate that in the X-band and Ku-band frequency range an iceberg can be modelled as a target composed of a number of large (on the wavelength scale) slightly rough (on the wavelength scale) surfaces. Empirical fitting of Ku-band scatterometer data (measured normalized radar cross section values) to an average incoherent normalized radar cross section statistical model for a slightly rough surface employing a Gaussian surface height correlation coefficient shows that such a model is applicable to a slightly rough iceberg surface. The model at 9.5 GHZ (horizontal polarization) is shown to give good agreement with independent measurements made by other researchers after making some general assumptions. It predicts that vertical polarization will give higher normalized cross sectional values. Higher frequencies will give higher values for incidence angles less than about 50° from the vertical. Through the use of standard target modelling techniques this normalized radar cross sectional model can be applied in a practical manner to provide a quantitative assessment of the detection capability of icebergs on current commercially available marine radars.