Measurements of Ocean Wave Spectra and Modulation Transfer Function with the Airborne Two Frequency Scatterometer

The results of this research show that the directional spectrum and the microwave modulation transfer function of ocean waves can be measured with the airborne two frequency scatterometer-microwave resonance technique. The results here are favorable to the future application of this or similar techniques from airborne or spaceborne platforms. Similar to tower based observations, the aircraft measurements of the modulation transfer function show that it is strongly affected by both wind speed and sea state. Also detected were small differences in the magnitudes of the MTF between downwind and upwind radar look directions, and variations with ocean wavenumber. Unexpected results were obtained that indicate the MTF measured from an aircraft is larger than that measured using single frequency, wave orbital velocity techniques such as tower based radars or “ROWS” measurements from low altitude aircraft. Possible reasons for this are discussed. The ability to measure the ocean directional spectrum with the two frequency scatterometer, with supporting MTF data, is demonstrated.