Serious errors have been discovered in the Defense Ministry's survey report on candidate sites for the deployment of land-based missile interceptor systems.
The so-called "Aegis Ashore" systems are designed to detect ballistic missiles launched toward Japan, using radar, and intercept them in outer space. If there are high mountains near the systems, it adversely affects their radar functions.
In its survey, the Defense Ministry concluded that nine of the candidate sites in the Tohoku region in northern Japan were unsuitable because the angle at which the radar is aimed at mountains near these sites exceeded 10 degrees. However, it subsequently turned out that the angles were less than the figures reported for all these sites.
The ministry has explained that the false data is attributable to an elementary mistake of calculating the angle without noticing that the reduced scale of the vertical axis (the height of the mountains) and that of the horizontal axis (distance to the mountains) at these sites were different. However, the report says the angle at one site was 15 degrees although the actual figure was only 4 degrees. Therefore, the matter should not be downplayed as a mere simple error.
In deciding to introduce the Aegis Ashore systems, the government deemed that one should be installed each in eastern and western Japan to cover all parts of the Japanese archipelago. The government has selected the Ground Self-Defense Force Araya Maneuver Area in the northwestern Japan city of Akita and the force's Mutsumi Maneuver Area in the western Japan Prefecture of Yamaguchi as potential host sites.
The Defense Ministry conducted the survey to explain to local bodies the safety of the systems and the reasons for selecting these locations as the host sites. The errors were found in data in candidate sites in eastern Japan.
At four of the nine sites, the angles were reduced to 10 degrees or less as a result of corrections. Despite this, the Defense Ministry has not changed its judgment that all nine sites are not suited to host the Aegis Ashore systems nor clarified the reasons for that. It is only natural for the public to suspect that the ministry had pre-determined that the Araya Maneuver Area was the only suitable location as the site for the deployment of an Aegis Ashore system in eastern Japan.
It is essential for the government of a democratic country to win public confidence in promoting security policy. Such a perfunctory survey conducted based on the conclusion that an Aegis Ashore system that will cover eastern Japan should be deployed to the Araya site would only damage the public's trust in Japan's defense policy.
Residents near potential sites for Aegis Ashore systems are worried that the sites could be attacked by other countries in case of a contingency. Concerns also remain about the impact of strong radio waves from the systems' high-performance radars on local residents' health and livelihoods.
The survey reports show figures that the ministry hopes will dispel such concerns but they are far from convincing for the public. Local governments cannot judge whether they can host such missile interception systems from this data. The Defense Ministry should closely re-examine the data including those on candidate sites in western Japan.
There is speculation that the government is hastily trying to introduce the ground-based missile interception systems under pressure from U.S. President Donald Trump to buy U.S.-made weapons.
If Japan really needs to introduce Aegis Ashore systems, the government should provide a careful and thorough explanation.