Passive sonar depends on signals of opportunity to detect, track and localize targets. These signals are typically detected and then tracked using Kalman filter-type signal followers. Target motion analysis (TMA) is then used to estimate the target's range and, from this, its position, course and speed. The accuracy of TMA is strongly dependent on the duration of the available track. Initiating a second tracker in reverse time at the time of detection can reduce or eliminate the delay between

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... rget detection and localization. A detection and tracking system for a passive sonar using a towed array receiver is described and an example of reverse-time tracking using real data is provided. Reverse-time tracking is able to significantly increase the amount of track data that can be extracted from already available data, highlighting the need for improved data fusion. Potential improvements to this enhanced system through track association are discussed.