Research On Ocean Oil Slick Detection Using Bei Dou-reflection

The pollution of oil slick in the ocean is one of the most frequent and most serious pollution disasters.Once oil spill accident happens,it will not only affect people’s production,life and human health,but also destroy marine ecological environment.At present,the main methods used to monitor the oil spill are optical and microwave remote sensing technology,the optical remote sensing technology can not detect oil slicked in all weather and all day due to weather conditions,the microwave remote sensing technique has the advantages of monitoring all-weather detection ability,however,the observation model is often the side-scan imaging,which easily affects oil spill detection accuracy because of a large amount of speckle noise in imaging,and high cost monitoring.GNSS-R(Global Navigation Satellite System-Reflection)are capable of penetrating cloud cover and all day,low cost,wide-range and multi source which can be received in most parts of the ocean,and can provide real-time long-term observation in all-weather,and therefore it can also be applied to detect oil slicks technique.The application of GNSS reflected signals has become a new research hot point in the field of remote sensing detection.The GNSS direct signal can provide accurate location information,accurate time information and accurate navigation information.The GNSS reflected signal through reflecting surface will carry lots of the characteristic information of target detection reflectors,and the reflection signal’s waveform,delay and Doppler frequency shift can be accurately mapped in the reflecting surface.Accordingly,the inversion and measurement of the physical properties reflectors can be achieved.Moreover,the main application fields of GNSS-R technology have soil moisture detection,sea ice detection,sea wave height measurement,sea surface height measurement,sea surface wind measurement,moving target detection and so on.At present,the existing GNSS-R oil spill detection technology is still in its infancy and not very mature.The feasibility of simulation detecting sea surface oil slicks using GNSS-R technology of delay-Doppler map(DDM)has been proposed by foreign scholars E.Valencia et al(2011).Internal scholars have only just begun using GNSS-R technology to detect oil spill sea surface.Previous studies focus mainly on oil spill simulation detection using GPS Medium Earth Orbit(MEO)satellites orbit parameters.Compared with GPS other existing satellite systems,the Chinese Bei Dou system is an independent research,independent operation,open and compatible of Global Satellite Navigation System,which is made up of three different hybrid constellation including MEO satellites,Inclined Geosynchronous Orbit(IGSO)and Geo-stationary Earth Orbit(GEO)satellites.Based on the above characteristics of Bei Dou,it can provide a long-term and effective monitoring tool for the marine environment in our country.In this paper,to assess the feasibility of the Bei Dou-R simulation in detecting the oil slicks,Bei Dou unique hybrid constellation is used.Coastal monitoring systems for oil slick simulation using two Bei Dou IGSO and MEO satellites are conducted on the basis of a realistic oil spill accident.The delay-Doppler map is conducted by combining the Zavorotny-Voronovich(Z-V)scattering model and clean ocean/oil-slicked surfaces of Mean-Square Slope(MSS)model,which can fully reflect the characteristics of the GNSS scattering signal of the sea surface condition.By comparative analysis of simulation results,the paper verified that it is feasible to distinguish oil slicks using Bei Dou-R technology,and a comparison of Bei Dou MEO DDM inversion oil slicks results and Bei Dou IGSO DDM inversion oil slicks results revealed that IGSO’s can better inversion of oil slick distribution.This paper supplemented the existing methods of oil spill detection and broaded the application scope of Bei Dou navigation system.The paper has the main contents as the following parts:1.This paper introduces the Bei Dou satellite constellation,the signals and the reflected signals of the correlation function.Based on the characteristics of electromagnetic wave sea surface scattering signals,the principle of the typical time delay Doppler two dimensional correlation power is analyzed from the both the angle of delay and the Doppler frequency.2.Based on the geometric relationship of navigation satellite reflection signals,the paper analyzes the sea surface scattered signals correspond to the reflector differences in delay and Doppler frequency shift.This paper discussed the method combined with the Z-V scattering model and clean ocean/oil-slicked surfaces of Mean-Square Slope(MSS)model,and described that the basic principle of DDM detection oil slick technology and the calculation of the specular point.3.This paper describes the design of Bei Dou MEO satellite and IGSO satellite simulation system for monitoring realistic marine oil spill using the Bei Dou hybrid constellation technology.Comparison and analysis of both MEO and IGSO DDM detection oil slick results,the simulation results show that oil slicks are clearly distinguishable within a coverage area the specular point.4.This paper comprehensively analyzes the sea surface oil slick monitoring by Bei Dou-Reflection DDM technology.Through comparison and analysis of two obtained DDM results,this paper reveals that MEO inversion oil spil DDM results are better than IGSO’s in the coastal simulation experiment,and it is more suitable for the DDM detection of oil slick using Bei Dou-R.This paper offers a good foundation for detecting oil spills using Bei Dou system in the future.