PULSED ELECTROMAGNETIC SYSTEM FOR AIRBORNE SURVEILLANCE OF MINES IN SHALLOW WATER

A REVIEW OF SENSOR TECHNOLOGIES SHOWS THAT ELECTROMAGNETIC ENERGY AT FREQUENCIES BELOW 1 KHZ CAN PROVIDE A RELIABLE MEANS TO DETECT, IDENTIFY, AND LOCATE MINES IN SHALLOW WATER. A PULSED ELECTROMAGNETICINSTRUMENT COMPRISING A TRANSMITTER ENCIRCLING A SUPERCONDUCTIVE MAGNETIC RECEIVER PROMISES TO PROVIDE AN AIRBORNE SYSTEM CAPABLE OF RAPIDLY LOCATING MINES. ELECTRIC CURRENT PULSES IN THE TRANSMITTER ILLUMINATE TARGETS. THE INSTRUMENT CAN PROVIDE THE ANALOGUE OF RADAR AT FREQUENCIES LOW ENOUGH TO PENETRATE SEAWATER OF DEPTH \10 M. FIRST ESTIMATES SHOW THAT A PRACTICAL TRANSMITTER MOMENT, \10,000 A M2, CAN GIVE USEFUL SWEEP RATES AT A TOW SPEED OF >200 KNOTS FOR A PATH WIDTH EXCEEDING 30 M. WE PROPOSE BOTH ANALYSES AND FIELD MEASUREMENTS WITH A PROTOTYPE INSTRUMENT TO VERIFY THE FEASIBILITY OF OPERATING A SUPERCONDUCTIVE GRADIOMETER WITHIN A PULSATING ELECTRIC CURRENT AND TO DETERMINE EXPECTED INSTRUMENT PERFORMANCE.