Gravity gradiometry resurfaces

Abstract

“The Red October was heading southwest on…Gorshkov’s Railroad. His speed was thirteen knots…. Installed in the…keel was a highly sensitive device called a gradiometer, essentially two large lead weights separated by a space of one hundred yards. A laser-computer system measured the space between the weights down to a fraction of an angstrom. Distortion of that distance or lateral movement of the weights indicated variations in the local gravitational field…. With careful use of gravitometers…he could plot the vessel’s location to within a hundred meters….”