Improved Ocean Surface Velocity Precision Using Multi-Channel SAR

Multi-Channel Synthetic Aperture Radar Based Classification of Maritime Scenes

“…Our experimental results, performed on imagery captured by the U.S. Naval Research Laboratory (NRL) airborne MSAR system [5,8,9], demonstrate how the motion information furnished by an MSAR system can be systematically used to enhance maritime scene classification in a manner that is superior to purely amplitude-based approaches. The MSAR airborne system operates at X-band with a center frequency of 9.875 GHz and uses linear frequency modulated chirped waveforms with a bandwidth of 220 MHz to achieve a range resolution of approximately 0.7 m. The peak radiated power is approximately 1.4 kW, while the aggregate pulse repetition frequency (PRF) of 25 kHz and pulse length of 6 μs produced an average power of 210 W. The system flies on a Saab 340 aircraft using a belly-mounted radome with a nominal incidence angle of 70°.…”

“…We utilize MSAR's imagery from multiple along-track phase centers to correct motion-induced displacements. These position corrections can be achieved using methods such as Velocity SAR (VSAR) [5][6][7][8][9][10] or Along-Track Interferometry (ATI) [5,29]. Here we use the VSAR algorithm which repositions all of the backscatter generated from a given target, regardless of its associated Doppler velocity and displacement, to a more compact, corrected position.…”

“…Here we use the VSAR algorithm which repositions all of the backscatter generated from a given target, regardless of its associated Doppler velocity and displacement, to a more compact, corrected position. The VSAR procedure has been extensively described elsewhere [5][6][7][8][9][10], although here we retain the complex pixels throughout. Specifically our VSAR processing steps are 1) Form image stack using each of the M phase center images.…”

“…The VSAR processing then corrects this image stack, repositioning the targets to their actual in-scene locations. The VSAR procedure has been presented previously [5][6][7][8][9][10], however in the method presented here we perform the VSAR correction retaining the coherent, complex data for each channel. This allows the M × M covariance matrix of the VSAR corrected image pairs to characterize the in-scene motions observed by the MSAR system.…”

“…In such cases, traditional approaches to scene induced motion compensation are known to be inadequate [5]. Recently, Multi-channel SAR (MSAR) imaging has been demonstrated as a powerful approach to systematically ameliorating the aforementioned scene induced motion error problem [5][6][7][8][9][10]. In particular, the additional along-track receivers provide new, independent information about the scene that can be used to correct automatically for the underlying scene motion.…”