This paper presents a fundamental simulation method to generate synthetic aperture radar (SAR) images for moving ocean surfaces. We have designed the simulation based on motion induced modulations and Bragg scattering, which are important features of ocean SAR images. The time domain simulation is able to obtain time series of microwave backscattering modulated by the orbital motions of ocean waves. Physical optics approximation is applied to calculate microwave backscattering. The computational grids are smaller than transmit microwave to demonstrate accurate interaction between electromagnetic waves and ocean surface waves. In this paper, as foundations for SAR image simulation of moving ocean surfaces, the simulation is carried out for some targets and ocean waves. The SAR images of stationary and moving targets are simulated to confirm SAR signal processing and motion induced modulation. Furthermore, the azimuth signals from the regular wave traveling to the azimuth direction also show the azimuthal shifts due to the orbital motions. In addition, incident angle dependence is simulated for irregular wind waves to compare with Bragg scattering theory. The simulation results are in good agreement with the theory. These results show that the simulation is applicable for generating numerical SAR images of moving ocean surfaces.
References
[1]
Alpers, W.; Rufenach, C.L. The effect of orbital motions on synthetic aperture radar imagery of ocean waves. IEEE Trans. Ant. Prop. 1979, AP-27, 685–690.
[2]
Alpers, W.; Rossand, D.B.; Rufenach, C.L. On the detectability of ocean surface waves by real and synthetic aperture radar. J. Geophys. Res. 1981, 86, 6481–6498.
[3]
Raney, R.K.; Vachon, P.W. Synthetic aperture radar imaging of ocean waves from an airborne platform: Focus and tracking issues. J. Geophys. Res. 1988, 93, 12475–12486.
[4]
Wright, J.W. A new model for sea clutter. IEEE Trans. Ant. Prop. 1968, 16, 217–223.
[5]
Yoshida, T.; Rheem, C.-K.; Ano, K. Numerical simulation of microwave backscattering from sea surface. J. Jpn. Soc. Nav. Archit. Ocean Eng. 2010, 12, 115–123.
[6]
Silver, S. Microwave Antenna Theory and Design; Peter Peregrinus Ltd.: London, UK, 1949; pp. 144–168.
[7]
Alpers, W. Monte carlo simulations for studying the relationship between ocean wave and synthetic aperture radar image spectra. J. Geophys. Res. 1983, 88, 1745–1759.
[8]
Nunziata, F.; Gambardella, A.; Migliaccio, M. An educational SAR sea surface waves simulator. Int. J. Remote Sens. 2008, 29, 3051–3066.
[9]
Harger, R.O. The synthetic aperture image of time-variant scenes. Radio Sci. 1980, 15, 749–756.
[10]
Franceschetti, G.; Iodice, A.; Riccio, D.; Schirinzi, G. SARAS: A synthetic aperture radar (SAR) raw signal simulation. IEEE Trans. Geosci. Remote Sens. 1992, 30, 110–123.
[11]
Franceschetti, G.; Migliaccio, M.; Riccio, D. On ocean SAR raw signal simulation. IEEE Trans. Geosci. Remote Sens. 1998, 36, 84–100.
[12]
Hasselmann, K.; Hasselmann, S. On the nonlinear mapping of an ocean wave spectrum into a synthetic aperture radar image spectrum and its inversion. J. Geophys. Res. 1991, 96, 10713–10729.
Ouchi, K. Principles of Synthetic Aperture Radar for Remote Sensing; Tokyo Denki University Press: Tokyo, Japan, 2004; pp. 218–226.
[15]
Cumming, I.G.; Wong, F.-H. Digital Processing of Synthetic Aperture Radar Data: Algorithms and Implementation; Artech House: Norwood, MA, USA, 2005; pp. 69–164.
[16]
Mitsuyasu, H.; Honda, T. The high frequency spectrum of wind-generated waves. J. Oceanog. Soc. Jpn. 1974, 30, 185–198.
[17]
Valenzuela, G.R. Theories for the interaction of electromagnetic and oceanic waves—A review. Bound.-Lay. Meteorol. 1978, 13, 61–85.
[18]
Peak, W.H. Theory of radar return from terrain. IRE Int. Conv. Rec. 1959, 7, 27–41.
[19]
Shuchman, R.A.; Maffet, A.L.; Klooster, A., Jr. Static and dynamic modeling of a SAR imaged ocean scene. IEEE J. Ocean. Eng. 1981, 6, 41–49.
