https://crsreports.congress.gov
Updated December 21, 2022
Navy TAGOS-25 (Previously TAGOS[X]) Ocean Surveillance
Shipbuilding Program: Background and Issues for Congress
Introduction
The first of a planned class of seven new TAGOS-25 class
ocean surveillance ships was procured in FY2022 at a cost
of $434.4 million. The Navy wants to procure the second
ship in FY2025. The Navy’s proposed FY2023 budget
requests no FY2023 procurement funding for the program.
Meaning of TAGOS Designation
In the designation TAGOS (also written as T-AGOS), the T
means the ships 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. The TAGOS-25 program was
previously known as the TAGOS(X) program, with the (X)
meaning that the precise design for the ship had not yet
been determined. Some Navy budget documents may
continue to refer to the program that way.
TAGOS Ships in the Navy
TAGOS ships (Figure 1 and Figure 2) support Navy
antisubmarine warfare (ASW) operations. As stated in the
Navy’s FY2023 budget submission, TAGOS ships “use
Surveillance Towed-Array Sensor System (SURTASS)
equipment to gather undersea acoustic data. The ships 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-25 ship with its
SURTASS arrays.
Figure 1. USNS Impeccable (TAGOS-23)
Source: U.S. Navy photograph accompanying “Ocean Surveillance
Ships,” Military Sealift Command, accessed May 25, 2021.
Current TAGOS Ships
The Navy’s five aging TAGOS ships include four
Victorious (TAGOS-19) class ships (TAGOS 19 through
22) that entered service in 1991-1993, and one Impeccable
(TAGOS-23) class ship that entered service in 2000. As of
the end of FY2021, all five were homeported at Yokohama,
Japan. The ships use a Small Waterplane Area Twin Hull
(SWATH) design, in which the ship’s upper part sits on two
struts that extend down to a pair of submerged, submarine-
like hulls (Figure 2). 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 it has
features (including very good stability in high seas) that are
useful for SURTASS operations.
Figure 2. USNS Effective (TAGOS-21) in Dry Dock
Source: U.S. Navy photograph 070913-N-2638R-004 posted at
Wikimedia Commons, accessed May 25, 2021.
Figure 3. TAGOS Ship with SURTASS Arrays
Source: Detail from slide 13, entitled “TAGOS(X) Concept of
Operations (CONOPS),” in Industry Day briefing for TAGOS(X)
program, June 26, 2019, accessed May 26, 2021, at GovTribe.com.
