Synthetic aperture radar imaging of ship wakes in the Gulf of Alaska

Abstract

The Gulf of Alaska SAR experiment was conducted during March 9–14, 1984 to investigate SAR imaging of narrow‐V wakes in a deep mixed layer environment so that surface manifestations of ship‐generated internal waves would be made small. Five SAR flights were executed over large ships of opportunity in deep water where the mixed layer depth exceeded 100 m in all cases. SAR images were obtained in sea states 1–4. Range and azimuthally traveling ships were imaged. The incidence angles of azimuthally traveling ships ranged from 24° to 53°. The following results are reported: (1) The half angles associated with narrow‐V wakes are consistent with first‐order Bragg surface wave theory described by Case et al. (1984). (2) The decay rate along the bright arms of the narrow‐V wake is consistent with the combined viscous and radiation decay of short surface waves with first‐order Bragg wavelengths. (3) Narrow‐V wakes are observed in sea states 1–3 at incidence angles less than 45°, with the longest narrow‐V wakes bright‐arm observed being 3.3 km. (4) Turbulent wakes (dark band between the bright arms) are observed in sea states 1–4 at incidence angles less than 53°, with the longest turbulent wake length observed being 41 km. (5) Bright boundaries along one side of the turbulent wake are observed.