The purchase of the Remus 600 brings the ministry's Hydroid AUV fleet to five vehicles, a statement from Hydroid's parent company Kongsberg Maritime said.
Christopher von Alt, president and co-founder of Hydroid, welcomed the contract.
"The Remus 600 is ideally suited for this application, as, when fully configured, its exceptional endurance allows it to operate underwater for long periods in varying depths of water," he said.
SEA Corp., Hydroid's representative in Japan, negotiated the Ministry of Defense contract.
Earlier this year the Japanese Defense Ministry purchased four Remus 100 systems for investigating and mapping seafloor dispersion of contaminants as well as mine countermeasure operations.
The Remus 100, weighing around 80 pounds, operates in coastal waters up to 100 meters -- 330 feet -- and also is used by the U.S. Navy, Hydroid says on its Web site.
Because is it suited to shallow waters, the 100 often is used for survey, security and clearance operations in harbors and also for fisheries work and scientific sampling.
The 600 version, designed with funding from the U.S. Office of Naval Research, is an endurance version of the 100 AUV and has an operating depth of 600 meters -- nearly 2,000 feet.
Hydroid also makes 1,500-meter and 3,000-meter versions.
The 600 is suited specifically to mine detection work including locating explosive devices and other undetonated ordnances as well as finding and classifying submerged objects.
Operating time for the 600 is up to 70 hours.
All Hydroid's AUV models have modular hull construction allowing them to be disassembled for reconfiguration, maintenance or shipping.
Hydroid's parent company, Kongsberg Maritime has an office in Houston and its headquarters in Kongsberg, Norway.
Kongsberg Maritime products include joystick systems, marine automation and information systems, navigational aids, propulsion control systems and tank gauging systems.
Hydroid was set up in 2001 specifically to manufacture, support and develop the Remus AUV systems originally developed by the Woods Hole Oceanographic Institution.
At the time of Kongsberg's acquisition announcement of Hydroid in December 2007, the business had estimated sales of around $20 million.
Kongsberg paid around $80 million on a debt-free basis for Hydroid which is headquartered in Pocasset, Massachusetts, Kongsberg says on its Web site.
The Hydroid deal was done through Kongsberg's subsidiary Simrad North America, a manufacturer of underwater sonar and sound systems for fisheries and research.
Kongsberg said at the time that Hydroid's REMUS vehicles would complement Kongsberg Maritime's HUGIN AUV activity that began in 1995 as a joint project with the Norwegian Defense Research Establishment called FFI and StatoilHydro.