EM61-MK2 Response of Standard Munition Items

Abstract : Target response coefficients for 13 commonly encountered UXO items were calculated from measurements made using the recently developed NRL Time-domain Electromagnetic Induction array. These response coefficients were used to predict the signals expected from an EM61-MK2, the most commonly used geophysical survey instrument for UXO, for each of these items as a function of orientation and distance of the center of the item below the bottom coil of the sensor. A series of EM61-MK2 survey measurements were made over the object at the NRL Blossom Point Test site to confirm the predictions. These predicted EM61-MK2 signals are presented graphically with the confirming survey measurements plotted on the same axes. The minimum signal at each of the four gates available from the EM61-MK2 is tabulated for a depth corresponding to 11x the object's diameter, the de facto expectation for detectability with modern geophysical equipment, and all the results obtained electronically as a spreadsheet.