  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.
