Kanagawa Prefectural Police found floppy disks containing data on the Aegis destroyer's radar system and transmission frequencies in the home of a Maritime Self-Defense Force sailor during a probe of his Chinese wife on suspicion of violating the immigration law, investigative sources said Friday.
The unnamed MSDF petty officer is also suspected of having taken home data on other destroyer radar systems that may have been provided by someone higher in the MSDF.
Under the Protection of National Secrecy Law that covers the Japan-U.S. Mutual Defense Assistance Agreement, data on the capability of defense equipment are defined as special defense secrets. Kanagawa police believe the data on the Aegis ships fall into that category, the sources said.
As the petty officer second class is not in a position that gives him access to Aegis data, police suspect another MSDF member gave him the information, the sources said.
The petty officer is a crewman on the destroyer Shirane, part of the 1st Escort Flotilla based in Yokosuka, Kanagawa Prefecture. His wife was arrested in January, the sources said, without providing further details about her.
Aegis destroyers, developed by the U.S. Navy, are equipped with the best air defense systems in the world. They have high-performance, over-the-horizon radar that covers several hundred kilometers.
The MSDF currently has five Aegis destroyers.
In August, police found another MSDF sailor had copied data on foreign submarines from an MSDF base onto a compact disc and brought it home. He also made trips to Shanghai to visit a Chinese woman who worked in a karaoke bar he frequented.