Implementation Of A Gem-3 Array For Detecting And Discriminating Uxo

We have designed and built a non-synchronous, sequential array of GEM-3 sensors for use with<br>the Multi-sensor Towed Array Detection System (MTADS) with support from ESTCP. The roughly 2-<br>m square array consists of three, 96-cm diameter GEM-3’s in a triangular configuration. The individual<br>sensors transmit a composite waveform made up of ten frequencies from 30 Hz to 48 kHz for a single<br>1/30 s base period. Sequential operation allows two of these base periods for deconvolution and output<br>of the frequency-dependent response from each GEM-3. After allowing for a short coil settling time<br>between sensors, we achieve an array sampling rate of 9.8 Hz. Along with the GEM sensors, array<br>position and orientation are measured by a 3-antenna GPS system combined with an inertial motion unit.<br>Issues of array calibration and timing have been explored, and both testing and survey results will be<br>presented.