A characterization of the instantaneous wave front distortion characteristics in SW06 and ASIAEX 2001 data and strategies for exploiting lucky scintillations

Abstract

Long line arrays are highly susceptible to signal wave front distortions caused by random medium effects like internal waves. Effects include large localization errors, biases, and loss of array gain. In earlier work, we had showed evidence from real data [Kirsteins and Ge, IEEE UASP workshop, Oct. 2017] that lucky scintillations, i.e., moments when the instantaneous signal wave front is relatively undistorted, occur regularly at much shorter time scales even during periods of strong internal wave activity that could potentially be exploited to improve array processing in environments with apparently poor spatial coherence. To better understand the phenomenon of lucky scintillations and how they can be used in array processing, we characterize in this paper the instantaneous or short time signal wave front distortion behaviors of horizontal line array (HLA) data from the Shallow Water 2006 (SW06) and ASIAEX 2001 experiments provided by the Woods Hole Oceanographic Institute, examining the time scales and the rate at which these lucky scintillations occur. Our analysis suggests an alternative array processing strategy by collecting data snap shots over a time interval matched to the ocean random medium time scales and using only the best snap shots in the estimator.