Lockheed Missiles and Space Co., P.O. Box 3504, Sunnyvale, CA 94088-3504
Sonobuoy detection ranges predicted at shore stations for use by ASW (antisubmarine warfare) aircraft are based on historical data and on XBT (expendable bathythermograph) data that is typically at least 6 to 12 h old. The accuracy of such predictions is questionable as shown by measurements and analysis. Prediction accuracy needs to be improved to increase the effectiveness and lower the costs of antisubmarine search and barriers using sonobuoys dropped from ASW aircraft. These predictions can be improved during the mission by measuring the on-site sound propagation loss between a specially modified air-dropped electronic sound source, similar in concept to a long-lived MK 84 SUS sound projector, and the acoustic receivers in the air-dropped sonobuoys. The derived propagation loss, used in conjunction with the XBT-based predictions, can be used to more effectively select sonobuoy depths and patterns. The existing Mk 84 SUS projector could be modified to be neutrally buoyant and provide 140 ping seconds of preprogrammed transmissions over a 6-h life. The transmissions can be shaped for low probability of intercept or mimicry. Similar applications to improve sonar range prediction for surface ships are also addressed.