Abstract Results of an investigation of the acoustic response from manganese nodule deposits are presented. The purpose of the Sea Grant sponsored work was to develop mathematical models of nodule acoustic scattering for use in processing ocean sounding data. The ultimate project objective was to establish feasibility and then block out a system design for remotely sensing nodule abundance (i.e., areal mass-density) and mean size. Such a system would drastically reduce survey ship time in the preliminary surveillance phase of nodule mining exploration. Earlier results of the investigation were presented at the 1981 OTC in paper no. 4133. Additional results current to February 1982 are presented here as follows:Single nodule scattering. Results of computations are shown using an elastic sphere model. Scattering cross-section and scattering functions are presented along with a tentative comparison with laboratory measurements.Analysis of module spacing statistics from bottom photographs. Histogram for two dense deposits (mining grade) are presented in the form of a normalized radial distribution function (RDF). Existence of a definite exclusion length of between two and three mean radii was established. The module abundance (no. per unit area) is shown to be fairly in homogenous for length scales on the order of 30 to 50 mean radii.Multiple Scattering Analysis. Results using configurational averaging are presented for three cases: Narrow beam single scatter, simplified 3-D single scatter (Sumitomo's model) and second order scatter for a normally incident plane wave including spacing ocean floor. By using existing shipboard sounding statistics. Results for the last case indicate a phase shift of the second order scattered mean signal. Application of the results to sounding system design are discussed along with suggestions for a second generation system. Background Manganese nodules are found over vast areas of the world's deep ocean basins. The enormous economic potential of these deposits has stimulated the development of an extensive multi-national deepsea mining industry. The industry is now in the last stages of test and evaluation of prototype mining systems (Kaufman, 1980). Determination of location of potential mining sites where nodule abundance and mineral content are high enough to be economical for extraction (i.e., prospecting) is becoming increasingly important. Existing prospecting techniques involve combinations of spot-checking and deep-tow surveillance. Spot-checking involves lowering optical sensors, grab-samplers, box corers or dredges several miles (typically 5000 m) to the ocean floor where pictures are taken or videotaped and bottom samples are obtained. A bottom photograph of a typical high density nodule deposit is shown in Figure 2. The sampling is done to establish a bottom grid with known properties. Alternatively sensor packages can be towed from a "fish" containing photographic equipment, videotape equipment, side-scan sonar deposits (mining grade) are presented in the and transponders. The fish is usually towed at a low speed (1 m/sec or lower) a constant distance (about 10- to m) above the ocean bottom. Either way is very expensive and slow because of the very long cables and deck machinery needed to deploy and operate the sensor/sampling systems.