Radio Wave Scattering from Rough Surfaces -- Theory and Application to Ocean Remote Sensing with HF and Marine Radar

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Over the last 40 years, radars of various kinds have become important in novel ocean remote sensing applications. In this context, high frequency surface wave radars (HFSWRs), operating in the 3 to 30 MHz frequency band (wavelengths of 10 to 100 metres), have been successfully employed, and, more recently, X-band nautical radars, ranging in frequency from about 8 to 12 GHz (wavelengths of about 4 to 10 centimetres), have been similarly used.***For HF signals, the ocean surface acts as a good conductor, and the transmitted radiation travels well beyond the line-of-sight horizon, scattering from ocean waves and objects, such as ships, ice and icebergs, and low-flying aircraft, on and near the surface. Since the early 1980s, Memorial University (MUN) researchers, supported by NSERC, the offshore oil industry and various government agencies, have been addressing the challenges associated with modelling this many-faceted scattering process. The continued development of these models is critical to enhancing techniques used to extract information, such as waveheights, surface currents and target velocities, from the received signals. ***Since 2000, the radar team continues to extend its analysis from the monostatic case (co-location of transmitter and receiver), to include the bistatic mode, in which the radar transmitters and receivers may be widely separated. Also, ongoing work, involving mounting the radar antennas on moving platforms and the examination of ionospheric signal contamination, has the potential of increasing coverage at a reduced cost while improving the robustness of extraction algorithms.***Currently, the HFSWR research is being augmented by the development of improved techniques for measuring ocean surface currents, winds and waves with X-band radar. At X-band, the surface wave component is not significant and the radar range is essentially limited to line-of-site. However, the data provided is of a much higher resolution than at HF and may be used to provide fine-scale features (on the order of square metres) of the ocean surface in regions where HF systems typically provide averages over several square kilometres. ***In the case, of HFSWR, due to support from NSERC and other interested parties, Canada has become a world leader in both theoretical and applied aspects of radar remote sensing. Over the last three decades, the MUN work has added significantly to the body of knowledge in this field, while leading to the export of the technology internationally. In collaboration with government, industry and the scientific community, there is very good potential to extend the remote sensing capabilities of these systems as well as to support the newer initiatives involving marine radar. It is expected that the work undertaken under the umbrella of this proposal will continue to attract interest from the scientific and industrial communities as well as those involved in maritime security.**