Millimeter-wave Scattering In A Wind-wavetank

Abstract

M illim e t e r -wave 6; c at t e r o m e t e r measurements were conducted in the NRL wind- wave facility at No and 515°incidence as a function of wind speed. The doppler spectra are consistent with Bragg scattering, so comparison with two-scale model functions is valid. Such comparison reveals that much work remains to be completed before our underslanding of the capillary waves with which millimeter-wave scatterometers are in resonance with is complete. For the past several years, the Naval Research Laboratory has been conducting scattering experiments in a wind-wave facility. These experiments have included backscattering measurements at X-band (10 GHz) that are reported elsewhere (l), and measurements of the modulation transfer function (mtf) at that frequency and at Ka-band (35 GHz). The good agreement obtained between the X-band wavetank results and open ocean measurements at similar frequencies suggested that the wavetank datal may provide an excellent test of scattering theories developed based on open ocean measurements. Further, if the data are consistent with Bragg scattering at Ka-band, then the scatterometer becomes one of the few instruments capable of measuring waves in the capillary regime.