一种改进的基于逆Omega-K算法的海面场景SAR原始数据仿真方法
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摘要
合成孔径雷达(SAR)海面场景原始数据仿真是研究海洋动力参数(表面波浪、风矢量和洋流)的有效工具。目前海面场景原始数据仿真方法已经基于逆Omega-K算法实现了海洋运动参数的空间变化。但是目前仅仅讨论了正侧视情况下的海面场景仿真,应用范围有限,同时没有考虑Stokes漂流以及Bragg相速度的影响,而这两者都是存在于真实海面的。通常情况下为了反演得到海面流场的二维速度矢量,雷达需要从两个不同的方位方向观察海面的同一个区域,因此这就需要考虑大斜视的雷达波束,同时Stokes漂流和Bragg相速度是SAR海表面流场观测不容忽视的两种运动。本文在不改变原有正侧视逆Omega-K算法的情况下,通过增加重新计算零方位时刻的斜视波束中心位置坐标,并据此确定SAR原始数据在多普勒域的位置来将其扩展到大斜侧视逆Omega-K算法,并通过时域Stokes漂流公式到频域内离散化Stokes漂流公式的推导来加入Stokes漂流,以及根据Bragg散射机制加入了Bragg相速度。仿真结果表明,经过聚焦成像后的SAR图像很好的体现了真实海面波浪场的形状,同时能够很好地反演出设定的雷达径向流场速度,且流速精度误差控制在6%以内。最后也证明了Bragg相速度以及Stokes漂流对于海面流场的影响不可忽视。
Synthetic Aperture Radar(SAR) raw data simulation of ocean surface is an effective tool for studying ocean surface waves and currents. At present, the raw data simulation method of ocean surface has been realized with the spatial variation of ocean motion parameters based on the inverse Omega-K algorithm. However, only the side-looking simulation of sea scene is currently discussed. The application scope is limited, and the Stokes drift and Bragg phase velocity are not be considered simultaneously. Generally, for example, in order to retrieve a two-dimensional velocity vector of the sea surface current field, the radar needs to observe the same area of the sea surface from two different directions; therefore, a large squint-looking radar beam is needed. At the same time, Stokes drift and Bragg phase velocity are two movements that cannot be ignored in SAR sea surface observation. Without changing the original side-looking inverse Omega-K algorithm,we grafted the side-looking SAR raw data into the large squint side-looking inverse Omega-K algorithm by adding the strabismus beam center position coordinates at the zero-azimuth moment and determining the position of the original SAR data in the Doppler domain, and adds Stokes drift and Bragg phase velocity. The results show that the hypothetical current field can be well inversed and the accuracy can satisfy the requirements. The focused SAR image reflects the shape of the sea surface wave field very well.
Synthetic Aperture Radar(SAR) raw data simulation of ocean surface is an effective tool for studying ocean surface waves and currents. At present, the raw data simulation method of ocean surface has been realized with the spatial variation of ocean motion parameters based on the inverse Omega-K algorithm. However, only the side-looking simulation of sea scene is currently discussed. The application scope is limited, and the Stokes drift and Bragg phase velocity are not be considered simultaneously. Generally, for example, in order to retrieve a two-dimensional velocity vector of the sea surface current field, the radar needs to observe the same area of the sea surface from two different directions; therefore, a large squint-looking radar beam is needed. At the same time, Stokes drift and Bragg phase velocity are two movements that cannot be ignored in SAR sea surface observation. Without changing the original side-looking inverse Omega-K algorithm,we grafted the side-looking SAR raw data into the large squint side-looking inverse Omega-K algorithm by adding the strabismus beam center position coordinates at the zero-azimuth moment and determining the position of the original SAR data in the Doppler domain, and adds Stokes drift and Bragg phase velocity. The results show that the hypothetical current field can be well inversed and the accuracy can satisfy the requirements. The focused SAR image reflects the shape of the sea surface wave field very well.
引文
李俊慧,王洪,汪学刚等,2016.步进频SAR的波数域成像算法研究.现代雷达,38(7):25-31
高山,钱成春,王伟等,2002.深水Stokes漂流公式的一种新形式.海洋湖沼通报,(2):1-9
曹福祥,胡东辉,洪文,2009.一种改进的基于全数据集的星载ScanSAR多普勒中心估计方法.中国科学院研究生院学报,26(1):97-101
Cafforio C,Prati C,Rocca F,1991a.Full resolution focusing of seasat sar images in the frequency-wave number domain.International Journal of Remote Sensing,12(3):491-510
Cafforio C,Prati C,Rocca F,1991b.SAR data focusing using seismic migration techniques.IEEE Transactions on Aerospace and Electronic Systems,27(2):194-207
Calini A,Schober C M,2017.Characterizing JONSWAP rogue waves and their statistics via inverse spectral data.Wave Motion,71:5-17
Franceschetti G,Migliaccio M,Riccio D,1998.On ocean SARraw signal simulation.IEEE Transactions on Geoscience and Remote Sensing,36(1):84-100
Franceschetti G,Iodice A,Riccio D et al,2002.SAR raw signal simulation of oil slicks in ocean environments.IEEETransactions on Geoscience and Remote Sensing,40(9):1935-1949
Hansen M W,Collard F,Dagestad K F et al,2011.Retrieval of sea surface range velocities from Envisat ASAR Doppler centroid measurements.IEEE Transactions on Geoscience and Remote Sensing,49(10):3582-3592
Hara T,Plant W J,1994.Hydrodynamic modulation of short wind-wave spectra by long waves and its measurement using microwave backscatter.Journal of Geophysical Research:Oceans,99(C5):9767-9784
Harger R O,1980.The side-looking radar image of time-variant scenes.Radio Science,15(4):749-756
Harger R O,1981.SAR ocean imaging mechanisms.In:Beal R C,DeLeonibus P S,Katz I eds.Spaceborne Synthetic Aperture Radar for Oceanography.Baltimore,MD,USA:John Hopkins University Press,41-52
Harger R O,1986.The SAR image of short gravity waves on a long gravity wave.In:Phillips O M,Hasselmann K eds.Wave Dynamics and Radio Probing of the Ocean Surface.Boston,MA:Springer,371-392
Liu B C,He Y J,2016.SAR raw data simulation for ocean scenes using inverse omega-k algorithm.IEEE Transactions on Geoscience and Remote Sensing,54(10):6151-6169
Mao Y,Guo L X,Ding H F,2011.Numerical simulation for the sea echo spectrum of OTHR radar based on JONSWAP sea spectrum.In:Proceedings of 2011 IEEE International Conference on Microwave Technology&Computational Electromagnetics.Beijing,China:IEEE,3.
Martin S,2014.An Introduction to Ocean Remote Sensing.New York:Cambridge University Press,251-260
Rouault M J,Mouche A,Collard F et al,2010.Mapping the agulhas current from space:an assessment of ASAR surface current velocities.Journal of Geophysical Research:Oceans,115(C10):C10026
Statman J I,Rodemich E R,2007.Parameter estimation based on Doppler frequency shifts.IEEE Transactions on Aerospace and Electronic Systems,AES-23(1):31-39
Wang Z F,Wu K J,Dong S et al,2015.Effect of wave-induced Stokes drift on the dynamics of ocean mixed layer.Chinese Journal of Oceanology and Limnology,33(1):233-242
Yu Y,Pei H L,Xu C Z,2017.Parameter identification of JONSWAP spectrum acquired by airborne LIDAR.Journal of Ocean University of China,16(6):998-1002
高山,钱成春,王伟等,2002.深水Stokes漂流公式的一种新形式.海洋湖沼通报,(2):1-9
曹福祥,胡东辉,洪文,2009.一种改进的基于全数据集的星载ScanSAR多普勒中心估计方法.中国科学院研究生院学报,26(1):97-101
Cafforio C,Prati C,Rocca F,1991a.Full resolution focusing of seasat sar images in the frequency-wave number domain.International Journal of Remote Sensing,12(3):491-510
Cafforio C,Prati C,Rocca F,1991b.SAR data focusing using seismic migration techniques.IEEE Transactions on Aerospace and Electronic Systems,27(2):194-207
Calini A,Schober C M,2017.Characterizing JONSWAP rogue waves and their statistics via inverse spectral data.Wave Motion,71:5-17
Franceschetti G,Migliaccio M,Riccio D,1998.On ocean SARraw signal simulation.IEEE Transactions on Geoscience and Remote Sensing,36(1):84-100
Franceschetti G,Iodice A,Riccio D et al,2002.SAR raw signal simulation of oil slicks in ocean environments.IEEETransactions on Geoscience and Remote Sensing,40(9):1935-1949
Hansen M W,Collard F,Dagestad K F et al,2011.Retrieval of sea surface range velocities from Envisat ASAR Doppler centroid measurements.IEEE Transactions on Geoscience and Remote Sensing,49(10):3582-3592
Hara T,Plant W J,1994.Hydrodynamic modulation of short wind-wave spectra by long waves and its measurement using microwave backscatter.Journal of Geophysical Research:Oceans,99(C5):9767-9784
Harger R O,1980.The side-looking radar image of time-variant scenes.Radio Science,15(4):749-756
Harger R O,1981.SAR ocean imaging mechanisms.In:Beal R C,DeLeonibus P S,Katz I eds.Spaceborne Synthetic Aperture Radar for Oceanography.Baltimore,MD,USA:John Hopkins University Press,41-52
Harger R O,1986.The SAR image of short gravity waves on a long gravity wave.In:Phillips O M,Hasselmann K eds.Wave Dynamics and Radio Probing of the Ocean Surface.Boston,MA:Springer,371-392
Liu B C,He Y J,2016.SAR raw data simulation for ocean scenes using inverse omega-k algorithm.IEEE Transactions on Geoscience and Remote Sensing,54(10):6151-6169
Mao Y,Guo L X,Ding H F,2011.Numerical simulation for the sea echo spectrum of OTHR radar based on JONSWAP sea spectrum.In:Proceedings of 2011 IEEE International Conference on Microwave Technology&Computational Electromagnetics.Beijing,China:IEEE,3.
Martin S,2014.An Introduction to Ocean Remote Sensing.New York:Cambridge University Press,251-260
Rouault M J,Mouche A,Collard F et al,2010.Mapping the agulhas current from space:an assessment of ASAR surface current velocities.Journal of Geophysical Research:Oceans,115(C10):C10026
Statman J I,Rodemich E R,2007.Parameter estimation based on Doppler frequency shifts.IEEE Transactions on Aerospace and Electronic Systems,AES-23(1):31-39
Wang Z F,Wu K J,Dong S et al,2015.Effect of wave-induced Stokes drift on the dynamics of ocean mixed layer.Chinese Journal of Oceanology and Limnology,33(1):233-242
Yu Y,Pei H L,Xu C Z,2017.Parameter identification of JONSWAP spectrum acquired by airborne LIDAR.Journal of Ocean University of China,16(6):998-1002