T-AGS 60 class survey vessels operated by the US Naval Oceanographic Office
Kongsberg Underwater Technology, Inc., of Lynnwood, Washington USA reports the
successful completion of the first Multibeam Sonar System upgrade on the U.S. Navy
T-AGS 60 class survey vessels operated by the Naval Oceanographic Office. The installation
on the USNS Sumner (T-AGS 61) was completed in June 2007 in Sasebo, Japan. The project
involved decommissioning the EM 121A and EM 1002 multibeam systems and installation
of Kongsberg's newest seabed mapping technology, including:
- EM 120 (1° x 1°) - Deep-water Multibeam echo Sounder for mapping to full
- EA 600 (200, 38, 12 kHz) - Multi-frequency Single Beam echo sounder for
surveying at all depths
- SBP 120 (3° x 3°) - Deep-water Sub-Bottom Profiler for high-resolution sub-bottom
data to full ocean depth
Gondola measuring 8 meters across (athwartships) and over 14 meters in length.
- ADCP (supplied from Teledyne RD Instruments) - Multi-frequency Doppler Current
Profiler for shallow and deep current profiling
- EM 710 (0.5°x 1°) - Intermediate Depth Multibeam Echo Sounder
All of the acoustic sensors were installed on a newly designed "gondola" measuring
8 meters across (athwartships) and over 14 meters in length.
Sea Acceptance Tests
Numerous small targets on seafloor detected by EM 710. Some as small as 1m x 1m or less.
The Sea Acceptance Tests and performance evaluations were conducted in 1) the
deep-water environment of the southeastern Philippine Sea (Parece Vela Basin), 2)
the very deep southern Mariana Trench, and 3) the shallow-intermediate seafloor
depths around the islands of Saipan, Anatahan and Guam in the Mariana Island arc
chain. The EM 120 was tested to the deepest spot in the ocean, the Challenger Deep
in the Mariana Trench, that has a nominal depth of 11,000m. The system successfully
tracked bottom to full ocean depth while maintaining swath coverage in excess of
23 kilometers. The EM 710 tracked bottom to greater than 2,000m; covering a swath
of 1 km at that depth. The Saipan reef offered numerous target detection testing
opportunities. Analysis by NAVOCEANO and their representatives proved the EM 710
system capable of meeting IHO Special Order target detection requirements.
The SBP 120 system achieved penetration of at least 80-85m in the depth zones
tested (3,000- 11,000m), exceeding the contract requirements.
Shown above are images processed by Dr. Sungat Altis, NAVOCEANO. Opinions expressed
regarding the meeting of contract requirements are purely those of Kongsberg and
have not been reviewed or endorsed by Dr. Altis. The USNS Sumner Sea Acceptance
Test was followed by a comprehensive training program (conducted onboard the vessel)
covering all five sonar systems and custom software developed to meet system integration
and data format requirements. For example, the Kongsberg Data Logger provides for
remote control, logging and data routing of the EM 120, EM 710, SBP 120 and EA 600
through NAVOCEANO’s ISS-60 survey control and data management system. All work was
concluded on August 18, 2007.
The next vessel in this class of six scheduled for the Multibeam Sonar System
upgrade is the USNS Bowditch (planned installation - Spring 2008).