Description
Military Sealift Command's Special Missions program supports worldwide oceanographic programs with ships that perform acoustical, biological, physical and geophysical surveys. These ships gather data that provides much of the military's information on the ocean environment.

The collected data helps to improve technology in undersea warfare and enemy ship detection. The oceanographic and hydrographic survey ships' multibeam, wide-angle precision sonar systems make it possible to continuously chart a broad strip of ocean floor. One oceanographic ship surveys the sea bottom and collects hydrographic data,along with previous ships, having charted three-fourths of the world's coastlines. USNS John McDonnell (TAGS 51) makes it easier for navigators to find their way along well-traveled and not-so-familiar shipping routes.

Features
The John McDonnell-class of survey ships carries 34-foot survey launches for data collection in coastal regions with depths between 10 and 600 m and in deep water to 4,000 m. A small diesel is used for propulsion at towing speeds of up to 6 knots. SIMRAD high-frequency active hull-mounted and side scan sonars are carried.

The Pathfinder class of survey ships have three multipurpose cranes and five winches plus a variety of oceanographic equipment including multibeam echo-sounders, towed sonars and expendable sensors.

Background
USNS John McDonnell (TAGS 51) was laid down Aug. 3, 1989, and launched Aug. 15, 1990.

The contract for the Pathfinder-class of surveying ships was awarded in January 1991 for two ships with an option for a third which was taken up May 29, 1992. A fourth ship was ordered in Oct. 1994 with an option for two more. A fifth ship was ordered Jan. 15, 1997. Construction began on the sixth and final ship in the class in 1999. By early 2002, all six ships had been delivered and were performing active missions for MSC.

General Characteristics, John McDonnell Class

Builder: Halter Marine Moss Point, MS.
Propulsion: 1 GM EMD 12-645E6 diesel; 2,500 horsepower (1.9 MW) sustained; 1 auxiliary diesel; 230 horsepower (172kW); 1 shaft.
Length: 208 feet (63.4 meters).
Beam: 45 feet (13.7 meters).
Displacement: 2,054 tons (2,086.96 metric tons) full load.
Speed: 12 knots (13.8 mph).
Crew: 22 civilians, 11 scientists.
Homeport: No homeport assigned.
Ships:
USNS John McDonnell (T-AGS 51)

General Characteristics, Pathfinder Class

Builder: Halter Marine Moss Point, MS.
Propulsion: Diesel-electric; 4 EMD/Baylor diesel generators; 11, 425 horsepower (8.52 MW); 2 GE CDF 1944 motors; 8,000 horsepower (5.96 MW) sustained; 6,000 horsepower (4.48 MW); 2 Lips Z drives; bow thruster, 1,500 horsepower (1.19 MW).
Length: 328.5 feet (100.1 meters).
Beam: 58 feet (17.7 meters).
Displacement: 4,762 tons (4,838.42 metric tons) full load.
Speed: 16 knots (18.4 mph).
Crew: 28 civilians plus 27 scientists.
Homeport: No homeport assigned.
Ships:
USNS Pathfinder (T-AGS 60)
USNS Sumner (T-AGS 61)
USNS Bowditch (T-AGS 62)
USNS Henson (T-AGS 63)
USNS Bruce C. Heezen (T-AGS 64)
USNS Mary Sears (T-AGS 65)