Precision gravity gradiometer/AUV system

Unprecedented stealth in navigation at sea, both long and short term, is now achievable through the integration of a gradiometer/gravimeter inertial navigation system into an appropriate submersible platform. Several key accomplishments have advanced the technology of gravity and gradiometry. Highly accurate gradiometer tensor measurements of 1.0 Eotvos or better were made at sea using a fully integrated GPS/DGPS/INS/gradiometer system. These measurements are part of the ongoing oil exploration surveys by Bell Geospace, Inc. (BGI) using its retrofitted surface vessel Seacor Surf. Through a reversal in roˆles, whereby gravity gradient signatures are used as references, instead of oil deposit signatures, reference mapping can be accomplished, enabling stealth navigation to the order of 30 m. Additionally, to handle the rough sea condition that affects the fidelity and resolution of gravity gradient detection, a nonpowered submersible has been developed and built for BGI, which can house the presently sized full tensor gradiometer (FTG) system