At the request of the Office of the Secretary of Defense (OSD), Military Sealift Command oceanographic survey ship USNS Bruce C. Heezen (T-AGS 64), under the technical control of the Naval Oceanographic Office (NAVOCEANO), completed a bathymetric survey Feb. 6 to determine the viability of either a repair or replacement of a damaged cable at the hydroacoustic monitoring station located at Diego Garcia.

Survey data is needed to characterize the underwater environment so planning can be accomplished efficiently and effectively.

The damaged cable is part of the International Monitoring System (IMS), the key component of the Comprehensive Nuclear Test Ban Treaty (CTBT) verification regime. The IMS is comprised of 337 monitoring stations and laboratories which include seismic, hydroacoustic, infrasound, and radionuclide technologies. The data from the IMS is sent to an International Data Centre located in Vienna, Austria -- the home of the Comprehensive Nuclear Test Ban Treaty Organization (CTBTO) which oversees the implementation of the verification regime, as per the treaty. The data is processed by the CTBTO and distributed to all state signatories.

"Surveying the damaged cable is yet another example of NAVOCEANO applying relevant oceanographic knowledge in support of global security," stated Commanding Officer Capt. Greg Ireton. "We have the best oceanographers in the world, and I have every confidence that they will be able to assist in making the best decision for returning the station to its full mission capability."

The hydroacoustic station at Diego Garcia is comprised of two cables with three hydrophones located at the end of each cable. These cables originate on shore and lie in opposite geometries, one to the northwest and one to the southeast. The total length of the northwest and southeast cables is 221 kilometers and 70 kilometers, respectively. Damage in the northwest cable was confirmed March 2014, and has resulted in reduced acoustic detection coverages in the north central Indian Ocean region. The depth at the cable damage location is approximately 2,000 meters.

Working through the Fleet Oceanographic Survey Workshop process, the OSD established a requirement for a T-AGS survey which was recently completed. NAVOCEANO will present the results to hydroacoustics experts of the DoD in April, with final delivery in June. The data will be used by all the stakeholders to help make the repair or replace decision.

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