{'fraction_non_alphanumeric': 0.015552753257671291, 'fraction_numerical': 0.0008406893652795292, 'mean_word_length': 5.230366492146596, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Numerical Prediction of the Effects of Azimuthal Smearing on Sar Imaging of Ocean Waves Using the Subwindowing Technique

The subwindowing method of modeling synthetic-apertureradar (SAK) imaging of ocean waves is used to predict the effects of azimuthal smearing by random wind waves on the imaging process. Simulated images show that the image response to monochromatic swells that are imaged primarily by velocity bunching modulation decreases with increasing wind speed. The magnitude of this decreased response is more severe than that predicted by coherence time methods. Theoretical analysis and simulated images show that the SAR focus perturbation leading to maximum image contrast is approximately one-half the azimuthal phase velocity of the swell being imaged. The azimuthal cutoff and range rotation effects are predicted when the imaging of fully saturated, wind-generated wave spectra is simulated. In this case, the predicted magnitude of these effects are less severe than that predicted by coherence time methods. Thus, it appears that the velocity bunching modulation and azimuthal smearing effects are strongly interdependent, and cannot be treated separately. keywords: SAR, ocean, wave coherent combination of all scatterer responses ensures that the loss of coherence in the radar backscatter from the surface (due to the differing motions of the scatterers) is maintained. Thus, the resulting simulated images contain the effects of all surface motion directly; the theoretical resolution of the SAR need not be degraded by a scene coherence time to describe the azimuthal smearing. An additional advantage of this technique is that the propagation of the waves diuring the formation of the synthetic aperture is included, a phenomenon important in predicting the dependence of the image contrast on the focus setting of the SAR processor. Here, the subwindowing technique is used to model the SAR imaging of monochromatic swells and wind-generated wave trains that are propagating in arbitrary directions with respect to the SAR flight path. The effects of the azimuthal smearing on the imagingprocess are investigated, as is the impact of adjusting the focus setting of SAR when swells are imaged. The SAR parameters used in generating the images were derived from the JPL L-band SAR used during the TOWARD experiment [9], and are summarized in Table 1.