The Study On Simulation Of Inverting Ocean Wave Di-Rectional Spectrum For Spaceborne Spectrometer

The wave direction spectrum is a very important wave information.The ocean wave field statistical characteristics(effective wave height,period,wavelength,wave direction,wave steep,etc.)can be calculated by the wave direction spectrum.So it is extremely important to obtain a high-precision wave direction spectrum.The ocean wave spectrometer is a small incident angle true aperture radar which specializes in detecting the wave spectrum.The world's first spaceborne spectrometer SWIM(Surface Wave Investigation and Moni-toring)will be mounted on the China-French satellites to measure the global wave direction spectrum.In this paper,based on the principle of wave spectrum detection,the methods involved in the key steps of the wave spectrum inversion of SWIM are studied by means of simulation,including the different modulation spectrum estimation methods and their performance,the differen removal method of speckle noise and performance,the different mixed wave partition and the wave parameters Extraction method and its performance,help to improve the accuracy of the satellite spectrum analyzer SWIM detection wave spectrum and the application of spectrometer data level.Firstly,this paper introduces the principle of wave spectrum detection by spectrometer and the data processing flow of ocean wave directional spectrum inversion simulation platform.Then,the inversion performance of different modulation spectrum estimation methods(periodic graph method,Welch method,AR model method and minimum variance method)is studied,the simulation results show that the minimum variance method and AR model method's performance is better than other methods in a certain sea condition.And then the accuracy of the inversion of each method decreases slightly with the incidence angle of the radar center.Then,in view of the important influence of the speckle noise on the inversion performance of the wave spectrum,the formation mechanism and the removal method of the speckle noise of the received signal are mainly studied.The simulation results show that the posterior integration method and the cross spec-trum method are more suitable for the denoising,and the inversion accuracy is also good,which is in accordance with the performance requirement of the spectrometer.Another study in this paper is to divide the waves from mixed waves spectrum obtained by inversion.Most of the actual ocean is the coexistence of wind waves and swell,based on the wave superposition principle and the empirical wave pattern,the sea surface of the mixed wave is simulated in the forward simulation.In the inversion tion,using the separate-wavenumber method(considering the wave number and azimuth distribution of the wave direction spectrum)to extract the wind wave and swell components,calculate the wave parameters of each wave component and compare it with the theoretical reference value.