Inversion Of Ocean Wave Slope And Wave Direction Spectrum Based On Airborne Spectrometer Data

High accuracy real time ocean wave information is needed in the fields of meteorology, navigation, shipbuilding, ocean engineering and so on. Wave direction spectrum is important ocean wave information, which could provide statistical characteristics of ocean waves including significant wave height, wavelength, wave period, wave direction, wave steepness, etc. in somewhere and sometime, so wave direction spectrum acquisition is very important. The ocean wave spectrometer is a new type of microwave sensor designed to detect directional spectrum of ocean waves. It is a kind of real aperture radar with small incident angle and 360° azimuth rotating scanning. In 2018, the world's first spaceborne spectrometer SWIM(Surface Wave study and Monitoring) will be launched with the China-France oceanography satellite.This paper studies the wave direction spectrum inversion based on the measured data of airborne spectrometer. In the case of large incident angle range, the extraction method of modulated signal is discussed. Then, in view of the important influence of the speckle noise on the performance of ocean wave spectrum retrieval, the formation mechanism, statistical characteristics and removal methods of the sea speckle noise of the spectrometer are mainly studied. The wave direction spectrum is measured from the measured data of the spectrometer, and the inversion results are compared with that of the buoy data.Another main research content of this paper is the use of spectrometer data to achieve the wave slope inversion. Ocean wave slope is a basic physical parameter of the sea / gas interface, but it is still short of a large range of direct measurement methods. It is possible to obtain the two-dimensional scattering data of the sea surface with the incident angle and azimuth angle, which makes the remote sensing of the ocean wave slope possible. This paper establishes a wave slope inversion model of spectrometer based on the quasi-specular scattering approximation model, and determines the incident angle range of the inversion model of slope by comparing the simulation results of the physical optics model with the small incident angle sea surface scattering model. Based on the nonlinear least square inversion method, all parameters of the quasi-Gaussian wave slope are extracted from the two-dimensional scattering data of the airborne spectrometer.