A New Estimate for Doppler Spectrum When Operating Space-Based SAR Over the Ocean

Abstract

Mikhail B Kanevsky

As is known, when operating SAR over the ocean, the simple estimate of the Doppler spectrum (FFT transform of a signal realization) fluctuates strongly around the mean value (i.e. around the Doppler spectrum itself). This circumstance does not allow the Doppler centroid to be accurately determined, which leads to errors in remote measurement of the current velocity on the ocean surface. The solution to this problem by accumulating a sufficient quantity of the estimates mentioned above is hardly possible due to the high speed of the SAR carrier. Smoothing a single estimate with a sliding window also does not guarantee that the centroid will not shift. Below we propose an estimate that, firstly, smoothes the simple one and, secondly, unlike smoothing using a sliding window, reproduces the shape of the Doppler spectrum, preserving the position of its centroid in a statistical sense.

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