The Defense Ministry plans to use U.S. defense giant Lockheed Martin Corp.'s SPY-7 radar system for its planned Aegis-equipped vessels, though the system is intended for use on land.
The Aegis ships will be built as an alternative to the Aegis Ashore ground-based ballistic missile defense system, which Japan once decided to introduce but later changed its mind.
The ministry will make the unusual move of installing on ships the SPY-7, which had been selected for the Aegis Ashore system.
In the radar selection for the new vessels, the SPY-7 competed with Raytheon Technologies Corp.'s SPY-6, which has been adopted by the U.S. Navy.
Tokyo judged that the SPY-7 is better in terms of performance and costs based on explanations by the U.S side. But the costs may balloon as the ships will have to be built bigger.
In June last year, Japan scrapped its plan to deploy the Aegis Ashore system in Akita Prefecture and Yamaguchi Prefecture, and later decided to build the new ships as an alternative.
After a year, however, the operational concept and total costs of the alternative plan are yet to be finalized.
"We again confirmed that the use of the SPY-7 would be most appropriate, based on information from the U.S. Missile Defense Agency and Navy," Defense Minister Nobuo Kishi told a press conference.
Japan will import the SPY-7 from Lockheed Martin through agent Mitsubishi Corp.
Washington will bear no direct responsibility for the transaction, unlike deals under the U.S. Foreign Military Sales program to provide military equipment to other countries.
The SPY-7 will serve as the "eyes" to protect the Japanese archipelago from ballistic missiles. It is a smaller version of the LRDR, a long-range missile warning radar for the defense of the U.S. mainland to be deployed in Alaska.
Japan will bear the costs of testing the missile detection and tracking capability of the SPY-7.
It is uncertain how much an actual firing test using interceptor missiles will cost. But the costs will add to the expenses to build the two new Aegis vessels, estimated at over ¥500 billion in total.
According to a Maritime Self-Defense Force source, Aegis radars will be installed at four locations on the bridge to enable 360-degree surveillance, raising the center of gravity and thus requiring a design that reduces swaying from waves.
Moreover, the SPY-7 is heavier than conventional Aegis radars and the SPY-6.
In May this year, the ministry contracted with companies including Mitsubishi Heavy Industries Ltd. and Mitsui E&S Shipbuilding Co. for technical assistance needed to design the new Aegis ships for a total of ¥1.6 billion.
Behind the choice of the SPY-7 was ¥70 billion to ¥80 billion the Japanese government had spent on the assumption that the radar would be adopted.
"There was no turning back. We had no choice other than the SPY-7," a ministry official said.
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