Function: Ocean surveillance ships have a single mission to gather underwater acoustical data. The T-AGOS ships operate to support the anti-submarine warfare mission of the Commanders in chief of the Atlantic and Pacific Fleets.





History: A contract for the first SWATH ship, T-AGOS 19, was awarded in November 1986, and options for the next three were exercised in October 1988. These ships have the same WSC-6 communications, links and operating procedures as the Stalwart class. The keel for the first Impeccable class was laid down Feb. 2, 1993. The ship was more than 60 percent completed when the shipyard encountered difficulties. The contract was sublet to Halter Marine on April 20, 1995 to complete the ship. Planned christening date is early 1999.





Description: The ship is designed to tow an array of underwater listening devices to collect acoustical data. The ship also carries electronic equipment to process and transmit that data via satellite to shore stations for evaluation. The ship, the listening devices and electronic equipment are all part of a system called the Surveillance Towed Array System, or SURTASS. The Victorious class ocean surveillance ships are built on a Small Waterplane Twin Hull, or SWATH, design for greater stability at slow speeds in high latitudes under adverse weather conditions. The Impeccable class ships have a hull form based on that of the Victorious. Acoustic systems should include an active low frequency towed array, which has a series of modules each of which houses two high-powered active transducers. These can be used with either mono or bistatic receivers.





Background: Stalwart, along with two sister ships, was deactivated in the early 1990s when the end of the Cold War signaled a reduced submarine threat from the former Soviet Union, however, the Atlantic commander decided to convert the three ships for a new mission ? finding narcotics traffickers. They now support the Joint Interagency Task Force, East. The three Stalwart class ships have been modified for a drug interdiction mission. The underwater acoustic array was removed, and an air search radar, integrated display system, sophisticated communications suite and other special mission equipment were installed to detect and monitor suspected drug traffickers.





General Characteristics, Stalwart Class



Builders:

Tacoma Boatbuilding, Tacoma, WA





Power Plant:

Diesel-electric; four Caterpillar D 3988 diesel generators, 3,200 horsepower, two motors, 1,600 horsepower; two shafts; bow thruster; 550 horsepower





Length, Overall:

224 feet (68.28 meters)







Beam:

43 feet (13.11 meters)





Displacement:

2,262 long tons (2,298.3 metric tons) full load





Speed:

11 knots (12.66 mph, 20.37 kph), 3 knots when towing array





Crew:

18 mariners, five technicians and up to 15 Navy personnel











Ships:

USNS Prevail (T-AGOS 8)

USNS Assertive (T-AGOS 9)

USNS Bold (T-AGOS 12)







General Characteristics, Victorious Class



Builders:

McDermott Marine, Morgan City, LA





Power Plant:

Diesel-electric; four Caterpillar 3,512 diesel generators, two GE motors, twin screw 1,600 shaft hp; two bow thrusters; 2,400 horsepower





Length, Overall:

234.5 feet (71.48 meters)







Beam:

93.6 feet (28.53 meters)





Displacement:

3,396 long tons (3,450.5 metric tons) full load





Speed:

10 knots (11.51 mph, 18.52 kph), 3 knots when towing array





Crew:

19-22 mariners, 5 technicians and up to 15 Navy personnel











Ships:

USNS Victorious (T-AGOS 19)

USNS Able (T-AGOS 20)

USNS Effective (T-AGOS 21)

USNS Loyal (T-AGOS 22)







General Characteristics, Impeccable Class



Builders:

Tampa Shipyard/Halter Marine





Power Plant:

Diesel-electric; three diesel generators; two Westinghouse motors; 5,000 horsepower; twin screw shaft; two omni-thruster hydrojets; 1,800 horsepower





Length, Overall:

281.5 feet (85.80 meters)







Beam:

95.8 feet (29.2 meters)





Displacement:

5,370 long tons (5,456.18 metric tons) full load





Speed:

13 knots (14.96 mph, 24.08 kph), 3 knots when towing





Crew:

20 mariners, 5 technicians and up to 20 Navy personnel