Proceedings PaperThe Influence Of Processor Focus On Speckle Correlation Statistics For A Shuttle Imaging Radar Scene Of Hurricane Josephine
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The L-band synthetic aperture radar (SAR) aboard the space shuttle Challenger succeeded in imaging the surface wave field produced by Hurricane Josephine. A fresh wind sea travelling across the SAR ground track was recorded approximately 100 kilometers from the storm center under the influence of a large ocean swell generated approximately 20 hours earlier when hurricane winds were at their maximum intensity. Such a dynamic sea state accentuates the role of specular reflection by surface facets in the SAR imaging process and serves as a unique test of the Doppler clutterlock and autofocus algorithms employed by ground scene correlators. Along track image resolution is defined in terms of the average number of specular facets per meter and a random number of specular events per radar cell. Speckle correlation statistics computed from Shuttle Imaging Radar scenes of the hurricane are used to approximate the dynamic wavenumber response of the SAR instrument. Observations of exponential trends in two-dimensional autocorrelations of speckled image data support an equilibrium theory model of sea surface hydrodynamics. The concepts of correlated specular reflection, surface coherence, optimal Doppler parameterization and spatial resolution are discussed within the context of a Poisson-Rayleigh statistical model of the SAR imaging process.