Sensitivity Analysis Of Bistatic Radar Scattering Characteristics From Random Rough Sea Surface

Radar remote sensing is an active remote sensing technology widely applied to monitor the marine environment.It provides the capability to characterize advanced features of the sea surface on a global scale.Bistatic radar observation has gained increasing interest in marine remote sensing in recent years.It is used in the inversion of sea surface wind fields,salinity,and roughness.Currently,most bistatic scattering research focused on the specular region.However,some studies have shown that the specular region might not be the best configuration for the bistatic scattering of the sea surface.The scattering coefficient may provide more valuable information when applying a bistatic radar configuration distinct from the specular region.With the rapid development and application of bistatic radar technique,it has become increasingly urgent to explore the bistatic scattering of the sea surface.Therefrom,we aim to explore the bistatic scattering mechanism of the sea surface in depth and clarify the corresponding scattering property under different radar configurations in this study.To this end,we first explore the advantages of bistatic radar in marine applications by calculating and comparing the spectral width of the sea spectrum in both monostatic and bistatic modes.Afterward,the bistatic scattering model of the sea surface is established according to the sea spectrum and Advanced Integral Equation Model(AIEM).Subsequently,the sensitivity analysis of sea surface bistatic scattering to radar parameters and wind fields(wind speed and direction)is conducted to determine the optimal sensitivity polarization combination index for marine observations.The main content and conclusions are as follows:(1)This study from theoretically calculates and compares the observing spectral width of the sea spectrum in the bistatic scenario to that in the monostatic scenario.The results clearly show that the observing spectral width of the sea spectrum is much broader in the bistatic mode than in the monostatic mode.In addition,whether the radar works in the monostatic or bistatic mode,the observing spectral width of the sea spectrum is positively correlated with radar carrier Frequency.(2)This study implements the bistatic scattering model of the sea surface by the sea spectrum and the AIEM model to explore the potential of retrieving the ocean dynamic parameters by the bistatic radar scattering.The bistatic scattering properties of the sea surface are simulated under different configurations.We then analyze how physical parameters in terms of the incident angle,polarization mode,and sea surface wind field(wind speed and direction)influence the scattering properties of the sea surface.On this basis,we arrive at the spatial distributions of bistatic scattering for the parameters mentioned above.(3)This study further conducts the sensitivity analysis of the sea surface bistatic scattering to the radar parameters and wind field(wind speed and direction).By so doing,three sensitivity evaluation indices are proposed based on the combination of distinct polarizations.Subsequently,the sensitivities of sea surface bistatic scattering coefficient to radar parameters and wind field are discussed according to the proposed evaluation indices.Results suggest that the co-polarization ratio index is more sensitive to wind field and radar parameters,making it well suited for inverting the ocean dynamic parameters.In summary,this study could enhance our understanding of ocean microwave remote sensing mechanisms,which provides theoretical basis for the application of microwave remote sensing of ocean and a foundation for monitoring and inverting sea surface wind fields.