Extended-life sonobuoy measurements to improve ASW mission planning

Oceanographic and acoustic conditions are complex, dynamic, and often unknown in littoral areas, but success of Naval operations in these areas requires a good environmental characterization. Some conceptual designs for new long-life airborne sensors include 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 4 “single-shot” fixed sonobuoys, b) data collected with 4 extended-life sonobuoys drifting over 7 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 4 drifting buoys yield significantly better representations of the actual temperatures, ambient noise, and derived acoustic fields than 4 discrete measurements. Intelligent algorithms are used to place tactical sonobuoys at optimal locations. The calculated detection probabilities from the drifting buoy environment are 22% more accurate than those from the discretely measured environment.