Reliable Target Area of Uncertainty from an Underwater Acoustic Source(s)

The Phase II Buoy Localization and Uncertainty Estimation (BLUE) program is developing advanced algorithms and software to improve target localization error in air ASW multistatic sonar missions. Significant improvements in target localization come from three distinct technology advancements: better knowledge of sonobuoy motion, more accurate target tracks, and improved fine bearing measurements for specific coherent waveforms. Buoy state estimation (BSE) is cast in a general unscented Kalman filter / Gauss-Markov (UKF/GM) formulation which includes both acoustic and non-acoustic observations and achieves a factor of 4 or more better localization of buoys than direct blast approaches when GPS is not available. Cued target tracking (CTT) reviews data from previous sonar pings to recover below-threshold echoes that associate well with a triggering possible target detection. When these retrospective measurements are included in a multiple hypothesis tracker, target localization error is reduced by a factor of 2 –a factor of 4 improvement in area of uncertainty. Finally, fine bearing estimates (FBE) are made more accurate by using an integration over all pulses in a multi-pulse echo, rather than using an SNR-weighted average based on bearing estimates for each of the pulses. We are investigating both coherent and incoherent integration for multi-pulse FBE.