The purpose of the effort reported here is to investigate modern multi-target tracking algorithms for high frequency active applications. High frequency active sensor systems are currently being evaluated by the Navy to meet the Sea Power 21 Sea Shield objectives for force protection and port security. These systems have elementary baseline tracking capabilities and could benefit from incorporating an advanced acoustic multi-target tracking algorithm designed for distributed active sensors. The incorporation of an improved tracking capability is aimed at reducing the high rate of false tracks being reported during system testing. This effort used active measurements from prototype actve sonar sensors to demonstrate true multi-target tracking on structured test data provided by ARL/UT, assess overall tracking performance and identify areas requiring algorithm improvements. APPROACH The limited overall scope of this investigation required focusing on a single tracking method that was likely to demonstrate improvement over an existing baseline tracker. Several different tracking methods were considered for this study: Bayesian (e.g., particle filter), recursive (e.g., Kalman filter), and batch methods (e.g., Multi-Hypothesis Tracking and Probabilistic Multi-Hypothesis Tracking). The prototype active sonar system and associated baseline processing chain considered in this study is capable of producing high resolution target detections at a high rate relative to the expected target dynamics. Consequently, Bayesian methods were not investigated because they are best suited to applications involving highly non-linear or non-Gaussian state or process equations. Moreover, the baseline tracker is recursive and hence batch type tracking methods were made the focus of this study. Multi-Hypothesis Tracking (MHT) is a batch type tracking method that, under ideal conditions, enumerates all possible data association hypotheses and produces maximum likelihood estimates of the target track. For situations containing a significant amount of clutter or false detections the computational burden of MHT may require limiting the number of data association hypotheses. This modification makes the algorithm and implementation much more complicated and sacrifices any Report Documentation Page Form Approved OMB No. 0704-0188 Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to a penalty for failing to comply w...