Stalwart class auxiliary general ocean surveillance ships (T-AGOS) were a class of United States Naval Ship (USNS) auxiliary support Ocean Surveillance Ships commissioned between April 1984 and January 1990. Their original purpose was to collect underwater acoustical information using the Surveillance Towed Array Sensor System (SURTASS), a towed array passive sonar. The USNS Stalwart (T-AGOS 1), USNS Indomitable (T-AGOS 7), and USNS Capable (T-AGOS 16) were modified to support narcotics interdiction by removing SURTASS equipment and adding an air-search radar and tactical data link equipment.