On March 6, the Japan Maritime Self-Defense Force (JMSDF) commissioned the fourth Hibiki-class auxiliary ocean surveillance ship, strengthening Japan’s ability to collect underwater acoustic intelligence in surrounding seas.
Named JS Bingo「びんご」(with pennant number AOS 5204), the new vessel was inducted into the service’s 1st Ocean Surveillance Division at Kure Naval Base in Hiroshima Prefecture, shortly after being delivered by Mitsubishi Heavy Industries Maritime Systems. The handover ceremony took place earlier the same day at the company’s shipyard in Tamano City, Okayama Prefecture.
The division is the JMSDF’s only unit dedicated to operating ocean surveillance ships.
Ocean surveillance vessels act as the “ears of the sea,” gathering acoustic data and the unique signatures of submarines and other vessels operating in nearby waters.
Fourth ship in the Hibiki class
JS Bingo is the fourth ship of the Hibiki class, following JS Hibiki (AOS 5201) commissioned in 1991, JS Harima (AOS 5202) in 1992, and JS Aki (AOS 5203) in 2021.
All ships in the class are named after coastal sea areas known as “nada.”
The latest vessel takes its name from the Bingo Sea (備後灘, Bingo-nada) which an area of water in the central Seto Inland Sea. The ship was laid down in March 2024 and launched in February 2025. Construction cost about 19.6 billion yen (about $124 million) under a contract awarded in March 2023.
With a standard displacement of about 2,900 tons, JS Bingo is the same size as JS Aki and roughly 50 tons larger than the first two ships of the class, reflecting design updates introduced roughly three decades after the original vessels were built.
SWATH hull for stable acoustic monitoring
One of the defining features of the Hibiki class is its Small Waterplane Area Twin Hull (SWATH) design — a semi-submerged catamaran configuration rarely used on Japanese naval vessels.
The design consists of two torpedo-shaped submerged hulls connected to the upper structure by thin struts. Because much of the hull remains below the water surface, wave impacts are significantly reduced, allowing the ship to maintain stability and conduct sensitive acoustic measurements even in rough seas. The Hibiki-class has a top speed of 11 kt, according to the JMSDF. The vessels, each of which has a crew of 40, also feature a flight deck for helicopter operations.
SURTASS system for submarine detection
At the heart of the ship’s mission is the Surveillance Towed Array Sensor System (SURTASS), a long towed sonar array deployed from the stern. JS Bingo and JS Aki feature a more advanced SURTASS than that fitted onto the first two ships of the class.
The system consists of a low-frequency array of hydrophones capable of detecting underwater sounds across large distances. By towing the array behind the ship, operators can collect acoustic data from submarines and other vessels and identify their distinctive acoustic “fingerprints.”
The collected acoustic information is set to be transmitted to analysis units within the JMSDF’s operational network, including anti-submarine warfare (ASW) elements based at Yokosuka.
Expanding Japan’s underwater surveillance network
With the commissioning of JS Bingo, the JMSDF now operates four Hibiki-class surveillance ships, increasing the number of underwater sensors available to monitor activities in surrounding waters.
The class was originally developed during the late Cold War to track increasingly quiet Soviet submarines. Today, Japan faces growing undersea activity as China expands its submarine fleet and Russia introduces new submarine types.
The addition of the fourth ship provides the JMSDF with more “ears” in the ocean, strengthening its ability to detect and monitor submarines operating near Japan.
Unique rotational crew system
The 1st Ocean Surveillance Division introduced a rotational crew system in 2017 — the first in the JMSDF — and remains the service’s only unit operating under such a system.
Instead of assigning a fixed crew to each vessel, multiple crews rotate among ships to maximize operational availability.
Until recently, the division operated three vessels with four rotating crews. With the addition of JS Bingo, the JMSDF will shift to a five-crew system operating four vessels, increasing operational availability and enabling more continuous acoustic monitoring missions.
The division falls under the control of Oceanography ASW (Anti-submarine Warfare) Support Command at the Yokosuka naval base in Kanagawa Prefecture, south of Tokyo.
JS Bingo specifications:
Total length: 67.0m
Maximum width: 29.9m
Height: 15.3m
Draft: 7.5m
Type and number of engines: 4 diesel engines
Propulsion motors: 2
Number of shaft lines: 2
Shaft horsepower: 3,000
Main equipment: SURTASS device 1 set
