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T-AGOS 23 Impeccable
Swath-L (Large) Ocean Surveillance Ship

The mission of the T-AGOS 23 Class ships is to collect, process, and transmit acoustic data in support of the Integrated Undersea Surveillance System (IUSS) mission requirements. The ship will be operated by the Military Sealift Command (MSC) utilizing both civilian and naval personnel to carry out its mission. In short, this vessel is used by the military to track submarines, and is the quietest vessel the government operates, outside of submarines themselves. The unique hull form is one of the most impressive features of this massive 281-foot vessel.

Surveillance ships serve as a stable platform to gather underwater acoustical data. IMPECCABLE was specifically designed to deploy two underwater listening devices called surveillance towed-array sensor system (SURTASS) used to augment the Navy's antisubmarine warfare capability. The SURTASS mission is to gather ocean acoustical data and, through electronic equipment onboard, process and provide rapid transmission of antisubmarine warfare information via satellite to shore stations for evaluation and analysis.

The keel for the first Impeccable class was laid down Feb. 2, 1993. Ship was more than 60 percent completed when the shipyard encountered difficulties. The contract was sublet to Halter Marine in Pascagoula, MS on April 20, 1995 to complete the ship, with a planned christening date of early 1999.

On 01 November 2000 Friede Goldman Halter, Inc. announced the christening of the USNS Impeccable (T-AGOS 23) at their Pascagoula, MS yard. The remaining four ships of the program (AGOS 24-27) will not be constructed. The Government made the USNS IMPECCABLE (T-AGOS-23) available for repairs from 27 August 2001 through 26 September 2001. The Government projected that it would take 12 consecutive days to complete the Drydocking repairs. The ship is homeported at Saint Helena's Annex, Virginia.

The Small Waterplane Twin-Hull-Active (SWATH-A) T-AGOS is the third generation of T-AGOS. Originally designed as a multi-purpose hull configuration, only the SURTASS application has been implemented. This ship is 281 feet in length, has a beam of 95.9 feet, displaces 5,370 long tons, and is capable of sustaining speeds up to 12 knots.

Built on a small water plane area twin hull design for greater stability at slow speeds in high latitudes under adverse weather conditions, Impeccable class ships have a hull form based on that of Victorious. IMPECCABLE is larger and faster then her predecessors, VICTORIOUS Class ships. This vessel is a larger version of the SWATH-P (T-19 Class) ships with 47 extra feet in length and almost 2000 tons greater displacement. The ship is powered by a larger diesel electric propulsion system that generates 5000 shaft horsepower. The larger hull design provides the same stable, hospitable environment as the smaller SWATH-P platforms with the additional space, displacement and power needed to accommodate not only the passive acoustic system, but also Low Frequency Active sonar. The ship is crewed by approximately 20 civilian mariners, 10 technicians, and up to 20 Navy personnel. T-23's larger dimensions are necessary to provide accommodations for the 43 man crew, made up of a mix of military operators, MSC crewmen and O&M technicians.

The T-23 Class will be equipped with a vertical line active transmit array, a multi-frequency horizontal receiver array and a real-time processing and analysis suite to accomplish both the active and passive surveillance missions for which it was designed. In addition to primary acoustic mission equipment, T-23 is also outfitted with an extensive suite of navigation, communications, command and control and support equipment.

Acoustic systems 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. Oceanographic and hydrographic surveys, underwater surveillance, acoustic research and submarine support are just a few of the services these ships support. The ships are operated and maintained by civilian contractors. The Surveillance Towed Array Sensor is a linear array deployed on a tow cable. Information from the array is relayed via WSC-6 (SHF) SATCOM link to the shore. These ships have the same WSC-6 communications, links and operating procedures as the Stalwart class. SURTASS patrols are 60 to 90 days in duration.

The Surveillance Towed Array Sensor System [SURTASS] Low Frequency Active (LFA) is the active adjunct to the towed array. LFA adds an active transmit array and handling system, power amplification and control systems, an active signal processing and display receive system, and an environmental analysis system to the SURTASS Upgrade. A prototype LFA system has been installed on a leased commercial vessel, Cory Chouest, and operated as an interim LFA asset pending delivery of T-AGOS-23 (SWATH-A), which will be equipped with LFA.

T-AGOS ships are operated by the Military Sealift Command and are under the administrative command of Commander, Undersea Surveillance. They are deployed under the Operational Control (OPCON) of the Theater ASW Commanders, CTF 84 and CTF 12. Civilian technicians who operate and maintain the mission equipment man the SURTASS Operations Center (SOC), the nerve center of the ship. When operating with tactical forces, military detachments are embarked for onboard analysis and direct reporting to fleet units. A SURTASS mission consists of 60 days on station while towing an array of hydrophones that collect acoustic data.

On 16 August 2000 the Military Sealift Command awarded a three-year contract for more than $108 million to Maersk Line, Limited of Norfolk, VA, to operate and maintain all 14 MSC-owned Auxiliary General Ocean Surveillance T-AGOS class ships. The fourteen ships support four Department of Defense programs: the Navy's Surveillance Towed Array Sensor System (SURTASS) operations; Navy, Atlantic Fleet and U.S. Coast Guard counter drug initiatives; and the Air Force Electronic Systems Command's radar missile tracking system.

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Page last modified: 07-07-2011 12:58:32 ZULU