Remote detection of underground targets, such astunnels, bunkers, abandoned mines, and underground waste dumps isof great importance both to the military and to commercialinterests. Along with other geophysical techniques, gravityshould be included in an integrated package for target detection.Unfortunately, microgravity surveys are expensive, because makingprecise gravity meter readings is time consuming, and a preciseelevation survey is also needed for interpretation of data. Incontrast, vertical gravity gradient surveys do not requireprecise elevations and provide sharper definition of shallowtarget anomalies. To take full advantage of a gradiometer, onemust be able to take readings quickly so that sufficient surfacedata can be taken to spatially resolve and separate shallowfeatures from deeper targets of interest. This project will startdevelopment of a new portable vertical gravity gradiometer whichwill be sensitive enough to detect small tunnels and bunkers atdepths up to 20 meters and will allow a reading time of about aminute. In Phase I, a single axis stationary gravity gradiometerwill be constructed by differencing signals from twosuperconducting gravity sensors built into a common cryostat. Thegradiometer noise level will be measured, alternative methods tofurther decrease instrumental noise investigated, and the rapidand highly sensitive measurements demonstrated.Anticipated Results/Potential Commercial Applications as described by the awardee: A portable gravity gradiometer wouldhave numerous military, engineering, and environmentalapplications. These include: detection of tunnels, bunkers,abandoned mine workings, and sink holes (solution features), andthe monitoring of perimeters of high security areas or of sitesof underground waste contamination.
