Research On Key Technologies Of GNSS-R Sea Surface Wind Field Detection

Global navigation satellite system(GNSS)can not only provide positioning and timing services for user,the signal it transmit can be applied for remote sensing,namely GNSS-R(GNSS-Reflectometry).With its advantages such as high resolution in space and time,all-weather and low cost,after more than 20 years of development,it has been fully researched and developed in sea surface wind field,sea surface height,soil moisture,surface vegetation,sea ice and oil spill.In this thesis,the research topic is relevant to GNSS-R sea surface wind field detection.The relative theoretical bases are introduced first,such as the correlation features of GPS,which is a typical signal of GNSS,relative theoretical models including sea spectrum and scattering model,and then get the scattering signal correlation power distribution by Z-V model,and study the following aspects based on delay waveforms.The influential factors in GNSS-R geometric configuration which can influence the delay waveform have been analyzed.The difference between the tailing edge under adjacent wind speed is defined as the difference D,which represents the sensitivity to wind field under current Geometric configuration.The result shows that the regulation of the difference D is related to elevation angle,azimuth angle and wind angle,and the fit expression about difference D and GNSS satellite selection strategy are given.For the choosing of coherent integration time,the relationship between the distribution of the scattering power and the Doppler bandwidth under different wind fields is studied.The upper bound of the corresponding coherent integration time is given for each sea condition.It is proved that the best coherent integration time of the spaceborne case should be chosen as 1ms.The traditional processing method of reflection signal,coherent integral-noncoherent accumulation is difficult to meet the high sensitivity observation requirement of the spaceborne case,thus a coherent integration-coherent accumulation-noncoherent accumulation method is proposed.Taking the SNR of delay waveform trailing edge as criterion,the appropriate power accumulationscheme is given according to the current sea conditions,which optimize the hardware resource requirement and accumulation result.The signal processing flow of GNSS-R sea surface wind field detection is summarized,and retrieval the wind field in airborne and spaceborne experiment,and the processing flow is fed back and verified by the experiment result.