Multi-array passive search in a littoral environment

Abstract

Acoustic barrier tactics were developed during the Cold War for deep, uniform underwater environments. Oceanographic and acoustic conditions in littoral environments are extremely complex and dynamic. The spatial and temporal variability of low-frequency signal and noise fields in these complex environments destroys the basic homogeneous assumption associated with standard tactical search concepts. Genetic algorithms (GAs) have been applied to both the signal and noise parts of this problem to produce near-optimal, nonstandard search tracks that maximize probability of detection in such inhomogeneous noise fields. In the present work, a GA was used to optimize tactics of several passive searchers by constructing optimal barriers in complex, littoral environments. The dynamic ambient noise model (DANM) was used to produce realistic, low-frequency, directional noise fields, based on discrete ship tracks. The cost function to be minimized was the probability that a target crossed the barrier undetected. Both standard and GA-derived tactics were evaluated and compared. The results show the importance of nonstandard tactics and careful consideration of environmental complexity when designing optimal passive search tactics. [Work sponsored by NAVSEA under the LCS project.]