Detection of Underground Structures using an Airborne Cryogenic Gravity Gradiometer

125 Detection of Underground Structures using an Airborne Cryogenic Gravity Gradiometer--Quantum Magnetics, Inc., 7740 Kenamar Court, San Diego, CA 92121-2425; (619) 566-9200 Dr. Robert Penny, Principal Investigator Ms. Tracey F. B. Wrightson, Business Official DOE Grant No. DE-FG03-97ER82464 Amount: $74,967 Underground facilities can be used to covertly perform activities that violate the goals of nonproliferation or to hide other illicit activities. Detecting these underground facilities is a national priority. Some of the techniques from exploration geophysics lend themselves to application in this area. The challenge is to achieve sufficient detection sensitivity and speed of coverage to be useful. This project will develop a gravitational sensor capable of airborne operation. Minute deviations in the local gravitational field will be caused by the removal of soil necessary to have built the underground chamber. The sensor will detect this gravitational deviation. The greatest difficulty in achieving airborne operation is separating the effects of gravitational acceleration from those of vehicle acceleration. Experience in the construction of a previous generation of a cryogenic gravity gradiometer, which has already achieved impressive acceleration rejection and sensitivity in the laboratory, will be used to develop a next generation instrument suitable for airborne operation. Phase I will design an instrument that is both more robust than the previous design and that reduces the nonlinearities limiting the present instrument solely to laboratory operation. Phase II will construct a prototype demonstrating the operation of this more robust design. Commercial Applications and Other Benefits as described by the awardee: Development of a robust airborne gravity gradiometer will allow a practical method for mapping the density of the subsurface geology that may have been changed by manmade structures. Such an instrument will also be of great benefit in geophysical exploration for oil, natural gas, and minerals. By combining gravitational measurements with airborne magnetic measurements, the resulting data fusion from two independent material properties will help the discrimination of desired targets from sensor clutter.