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Report on Navy TAGOS(X) Ocean Surveillance Shipbuilding Program

The following is the Congressional Research Service May 27, 2021 In Focus report, Navy TAGOS(X) Ocean Surveillance Shipbuilding Program: Background and Issues for Congress.

From the report

The Navy wants to procure in FY2022 the first of a planned new class of seven TAGOS(X) ocean surveillance ships. The Navy estimates that TAGOS(X) ships will cost about $400 million each. The issue for Congress is whether to approve, reject, or modify the Navy’s funding requests and acquisition strategy for the program.

TAGOS Ships in the Navy 

TAGOS ships support Navy antisubmarine warfare (ASW) operations. As stated in the Navy’s FY2021 budget submission, TAGOS ships “use the Surveillance Towed-Array Sensor System (SURTASS) to gather undersea acoustic data. They also carry electronic equipment to process and transmit that data via satellite to shore stations for evaluation.” Figure 3 shows a simplified diagram of a TAGOS(X) ship with its SURTASS arrays trailing below and behind the ship.

In the designation TAGOS (also written as T-AGOS), the T means they are operated by the Military Sealift Command (MSC); the A means they are auxiliary (i.e., support) ships; the G means they have a general or miscellaneous mission; and the OS means the mission is ocean surveillance. In the program designation TAGOS(X), the X means that the new TAGOS ship’s precise design has not yet been determined.

Current TAGOS Ships

The Navy currently operates five aging TAGOS ships—four Victorious (TAGOS-19) class ships (TAGOS 19 through 22) that entered service between 1991 and 1993, and one Impeccable (TAGOS-23) class ship that entered service in 2000. As of the end of FY2020, all five were homeported at Yokohama, Japan.

The five in-service TAGOS ships are Small Waterplane Area Twin Hull (SWATH) ships. In a SWATH ship, the upper part of the ship sits on top of two struts that extend down to a pair of submerged hulls that look like submarine hulls. The struts have a narrow cross-section at the waterline (i.e., they have a small waterplane area). The SWATH design has certain limitations, but has features (including very good stability in high seas) that are useful for SURTASS operations.

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