Modeling the detection of small targets on the sea surface, considering the shading effect
Purpose of the work. Development of a complex mathematical model for detecting small-sized surface targets (e. g., boats with a radar cross-section of 2 m2) using a ground-based radar station (antenna height 10 m, frequency 10 GHz, vertical polarization) under sea wave conditions. The study aims to quantitatively assess the effect of target shadowing by wave crests on the signal-to-clutter ratio and detection probability under various sea states. Materials and methods. The model is based on a two-scale approach (TSM) with separation of the wave spectrum into large (gravity) and small (capillary) waves. The sea surface was generated by the method of harmonic superposition using the Pierson–Moskowitz spectrum for large waves and a modified Elfouhaily spectrum for small waves. The specific normalized radar cross-section of the sea surface was calculated using two-scale model formulas (Bragg scattering, polarization coefficients, wave asymmetry correction). Surface shadowing along the lines of sight, geometric shadowing of the target, and Earth's curvature were taken into account. Modeling was performed for three sea states on the Douglas scale: calm (1 point, wave height 0.15 m), moderate (3 points, 1.2 m), and rough (5 points, 3.25 m). For each state, 1000 realizations of the random wave field were generated, and the results were statistically processed. Results. It was established that the target's radar cross-section decreases from 1.95 m2 (1 point) to 0.14 m2 (5 points) due to shadowing by wave crests. The specific normalized radar cross-section of the sea surface (median value) increases from –48.4 dB to –30.9 dB when transitioning from 1 to 5 points. The signal-to-clutter ratio decreases from +8.1 dB in calm seas to –22.9 dB in rough seas.
Authors: A. A. Ivanov
Direction: Physics
Keywords: sea waves, effective scattering surface, shading, radar detection, small-size targets, mathematical modeling, signal-to-noise ratio, probability of detection
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