GPS Reference While Submerged

A stealthy underwater GPS-based position system is proposed. The system comprises a sparse network of “underwater satellites” selectively grouped to provide coverage over large ocean volumes where navigation assistance is desired. The Underwater Satellites use pulsed blue-green lasers to covertly transfer encrypted and authenticated position information to submerged (and/or surface) vessels operating at depth and speed. The Underwater Satellites can continue to provide precise position and navigation information even if the earth-orbiting GPS satellites are destroyed, jammed, spoofed or otherwise denied—an important war-time capability. Future extensions to the proposed system could provide contact detection and classification (“Red Force” tracking) and underwater communications at depth and speed. The primary technical challenge facing underwater laser communication is propagating the laser beam over meaningful distances. Laser energy is degraded by absorption and scattering from particulate matter suspended in sea water. We propose to research adaptive optics (AO) technology to measure, in-situ, the distortion induced by the seawater and to extend the propagation distance of the laser link by correcting those aberrations, in real-time, using deformable optics. We propose to research atom interferomtry as our time-keeping technology and investigate the accuracy achievable in the Underwater Satellite operating environment. The proposed system, enabling submarines and other submerged vessels to covertly receive GPS-based position information at depth and speed, with no dependence on the earth-orbiting GPS satellites, would reduce opportunities for adversaries to detect our submarine force and would improve operational effectiveness.