OVERVIEW: Active directional sonobuoys are expendable sonar devices deployed from aircraft or ships to detect and track underwater targets such as submarines. They emit focused acoustic pulses and listen for echoes, providing precise bearing information on contacts.

DETAILS: These sonobuoys contain a transmitter that sends out active sonar pings and a directional hydrophone array that receives the reflected signals. By analyzing the time delay and angle of returned echoes, they help operators localize underwater contacts with improved accuracy compared to omnidirectional sonobuoys. Active directional sonobuoys are widely used in anti-submarine warfare (ASW) to enhance detection in complex acoustic environments and to classify contacts. They transmit data via radio to the deploying platform for real-time analysis.

ROLE SUMMARY:
Category: Sonar Sensor
Primary Use: Submarine detection and tracking
Function: Emission of directed sonar pulses with directional echo reception
Strong Against: Submarines, underwater vehicles, low-noise targets
Weak Against: Quiet or deep-diving submarines, countermeasure clutter
Platform: Maritime patrol aircraft, ASW helicopters, surface vessels
Integration: Compatible with standard sonobuoy deployment and processing systems

SOURCE:
Janes Naval Sensor Systems
https://en.wikipedia.org/wiki/Sonobuoy