Impact of extended-life noise and temperature measurements on littoral ASW

The U. S. Naval Air Systems Command is considering extended-life environmental sonobuoy concepts to better characterize littoral environments. Some conceptual designs contain thermistors to measure ocean temperatures and hydrophones to measure ambient noise. In this work, measured temperature profiles and predictions of ambient noise using ship densities in the Sea of Japan are used to simulate (a) data collected with 3 “single-shot” fixed sonobuoys, (b) data collected with 3 extended-life sonobuoys drifting over a 12-days, and (c) “ground-truth” or actual conditions. Those environmental simulations are used to predict acoustic conditions; i.e., transmission loss, detection range, and detection probability at 100 Hz for an anti-submarine warfare application. The simulated environmental fields and predicted acoustic results for fixed and drifting sensors are compared to our best estimate of actual conditions. Results show that 3 drifting buoys yield significantly better representations of the actual temperatures, ambient noise, and derived acoustic fields than 3 discrete measurements. Intelligent algorithms are used to locate tactical sonobuoys in the three environments. The calculated detection probabilities from the drifting buoy environment are 20% more accurate than those from the discretely measured environment.