Gravimetric Radar: Gravity-Based Detection of a Point-Mass Moving in a   Static Background
  This paper discusses a novel approach for detecting moving massive objects based on the time variation that these objects produce in the local gravitational field measured by several detectors. Such an approach may provide a viable method for detecting stealth aircraft, UAVs, cruise, and ballistic missiles. By inverting a set of nonlinear algebraic equations, it is possible to use the time variation in the gravitational fields to compute the mass, position, and velocity of one or more moving objects. The approach is essentially a gravity-based form of triangulation. Based on order-of-magnitude calculations, we estimate that under realistic scenarios, this approach will be feasible if it is possible to design gravimetric devices that are four to five order of magnitude more sensitive than current devices. To achieve such a level of sensitivity, we suggest designing detectors that exploit a quantum-mechanical effect known as gravity-induced quantum interference. Furthermore, even if we have a perfect detector, it will be necessary to determine the magnitude of various atmospheric disturbances and other sources of noise. 
Emmanuel David Tannenbaum
physics.ins-det