a land-based form of Aegis missile defense system
The Japanese Ministry of Defense reportedly plans to defer deployment of THAAD in favor of an Aegis Ashore system.
The Asahi Shimbun newspaper, citing anonymous government sources, reported on June 23 that the ministry had asked the Japanese government to reflect the costs of deploying Aegis Ashore - a land-based form of Aegis missile defense system - in the 2018 budget. The 2017 Japanese government budget includes funds appropriated for preliminary investigations of possible deployments of both THAAD and Aegis Ashore.
But the Ministry of Defense now plans to request that THAAD-related costs be cut from the 2018 budget and only Aegis Ashore-related costs be included. The ministry appears set to officially decide on Aegis Ashore as a suitable ballistic missile defense (BMD) system for Japan next month, the newspaper reported. Defense Minister Tomomi Inada is currently coordinating plans with the US to visit an Aegis Ashore testing facility in Hawaii next month.
As recently as last year, the ministry was weighing introducing both THAAD and Aegis Ashore. In the past, Japan has had a twofold BMD system, with Aegis-equipped vessels positioned at sea to attempt primary interception outside the atmosphere using SM3 missiles, and land-based PAC-3 missiles to attempt interception of missiles once they have entered the atmosphere. An additional third system for intercepting missiles at high altitudes has also been discussed.
The ministry’s preference of Aegis Ashore over THAAD for defense against North Korean missiles comes down to cost-effectiveness.
THAAD has an interception radius of around 200 km, while the SM-3 Block 2A interceptor scheduled to be used with Aegis Ashore has a reported interception radius of over 1,000 km. According to the ministry, six THAAD launchers would be required to defend Japan’s entire territory, compared to two with Aegis Ashore. A single THAAD launcher costs upwards of 100 billion yen (US$898.6 million), while an Aegis Ashore launcher is expected to cost around 80 billion yen (US$718.9 million).
The Aegis Ashore
While US Forces Korea is responsible for deployment costs and management of the South Korean THAAD system, the Aegis Ashore system in Japan would be paid for by the Japanese government and managed by the Japan Self-Defense Forces, with the US military operating THAAD X-band radar installed in Aomori in northern Japan and Kyoto in southern Japan.
The reason China has not reacted sensitively to Japan’s THAAD radar is because of the country’s distance from the Chinese mainland.
“The SM-3 Block 2As that Japan plans to use with Aegis Ashore are weapons jointly developed by the US and Japan, which makes them cheaper than importing something the US developed,” explained one security expert.
“They’ve also acquired some knowledge of the SM3 because the Japan Maritime Self-Defense Force is already using it with its Aegis warships, which was probably a consideration,” the expert said.
The performance of the SM-3 Block 2A jointly developed by the US and Japan is not perfect. NHK reported on June 23 that a US interception test with the missile in Hawaii on June 21 had failed to take down its target. Development of the SM-3 Block 2A has been under way since 2006, and a successful interception was carried out in a February test.
By Cho Ki-weon, Tokyo correspondent
Please direct questions or comments to [email@example.com]