SUBMARINE COUNTERMEASURES AGAINST NEW TECHNOLOGY ACTIVE SONARS (U)

THERE ARE MANY TYPES OF ACTIVE SONAR THREATS THAT EXIST NOW OR WILLEXIST IN THE FUTURE. THESE THREATS POSE A CONSTANTLY CHANGING CHALLENGE TO COUNTER THEM. A VERY PROMISING COUNTERMEASURE TECHNIQUE THAT CAN BE USEFUL AGAINST A WIDE RANGE OF THREATS IS BEING RESEARCHED AND DEVELOPED. THIS TECHNIQUE, DESCRIBED IN THE MAIN BODY OF THIS PROPOSAL, PRESENTLY HAS LIMITATIONS INCLUDING THE ABILITY TO COUNTER A WIDE RANGE OF THREATS. A MAIN OBJECTIVE IS TO DEVELOP A SINGLE SYSTEM THATCAN COUNTER THE ENTIRE RANGE OF POSSIBLE THREATS. IN PURSUIT OF THISGOAL, A TECHNICAL ADVANCEMENT TO FREE THE COUNTERMEASURE TECHNIQUE OF ITS LIMITATIONS IS SOUGHT. A DISTANCE-SELECTIVE OPTICAL HYDROPHONEIS PROPOSED TO MITIGATE THE LIMITATIONS OF THE COUNTERMEASURE SYSTEM. IT OPTICALLY MEASURES THE ACOUSTIC SIGNALS AT A FIXED DISTANCE FROMTHE HULL, SO THAT THERE IS SUFFICIENT TIME TO PROCESS THE INSONIFICATIONS SIGNALS BEFORE THE PROPAGATING ACOUSTIC WAVES REACH AND REFLECTFROM THE HULL. THE SENSOR IS A UNIQUE HETERODYNE LASER SENSOR THAT USES THE FOCAL CUSP OF A FOCUSED LASER BEAM TO PROVIDE THE DISTANCE SELECTIVITY. THE SUSPENDED PARTICULATES IN THE OCEAN, WHICH CAN BE ENHANCED, PROVIDE THE OPTICAL REFLECTORS THAT WILL MOVE WITH THE MOVEMENTOF THE MEDIUM RESULTING FROM INSONIFICATION. THE PRESENT AND FUTURE ACTIVE SONAR THREATS WILL BE INVESTIGATED, AND THEIR CHARACTERISTICS AND VULNERABILITIES EXPLORED. THE SUSCEPTIBILITY TO THE DESCRIBED COUNTERMEASURE TECHNIQUE AND THE ADVANTAGE OF THE OPTICAL HYDROPHONE AGAINST THESE THREATS WILL BE INVESTIGATED.