Undersea GPS could guide submerged drones in the deep

Autonomous underwater vehicles like the Navy’s Bluefin-21 would use POSYDON for accurate positioning.

The Pentagon’s main research office, which is exploring the possibilities for an underwater Internet, also wants to create a kind of Global Positioning System constellation under the sea.

The Defense Advanced Research Projects Agency has issued a solicitation for a program that would place acoustic signaling sources around the ocean floor, functioning similarly to GPS satellites, so that submerged vehicles could get precise positioning information without having to surface. The Positioning System for Deep Ocean Navigation, or POSYDON, program also is looking to reduce the cost and power requirements of current underwater navigation sensors.

GPS provides worldwide coverage above the Earth’s surface, but its radio frequency waves are blocked under water, just like other high-frequency communications signals. Currently, submerged vessels use inertial measurement units and other dead-reckoning sensors to calculate their positions, DARPA said, but those sensors tend to provide accurate sole-source navigation only for short-term missions. On longer missions, vessels eventually have to surface to get a GPS reading, and in many situations, that surfacing can put them at risk.

Researchers are looking to seed the ocean with acoustic sources, giving vessels the ability to use multiple sources to obtain an accurate positioning fix, just like aircraft, ships and cars do on the surface with GPS. In the process of developing POSYDON, which has a 48-month notional timeline consisting of three phases, DARPA also wants to bring down the cost of undersea navigation. The agency said current state-of-the art inertial measurement units, Doppler velocity log systems and other underwater navigational sensors have significant cost and power requirements, which the agency is aiming to lower with the new program.

DARPA intends the system to serve autonomous underwater vehicles, although it will accept proposals for systems that could be used by other undersea vessels.

The program is tentatively set up for a 12-month Phase 1 focusing on signal processing and ocean modeling, followed by an 18-month Phase II for developing and demonstrating a real-time acoustic ranging capability, according to the solicitation. Phase III, which DARPA said will have its own solicitation, will be for demonstrating real-time positioning with an integrated system. Multiple awards are possible under the program.

Responses are due by June 11. DARPA notes that responses could include classified information, and the solicitation gives instructions for submitting confidential and secret information. A Proposer’s Day, limited to U.S. citizens with DOD Secret or higher clearance, is scheduled for May 1.