Japan Picked An Aegis Ashore Site Based On Miscalculations From Google Earth

Japanese officials have admitted that they miscalculated the angles of elevation of various mountains when deciding on where to base one of its two future Aegis Ashore ballistic missile defense systems. This led them to determine the only suitable site in eastern Japan was the Araya Maneuver Area, though nine others may have been viable.

Takashi Gomi, in charge of the Japanese Ministry of Defense’s strategy planning division, disclosed the error to reporters during a press conference in the city of Akita on June 10, 2019. The Japan Ground Self Defense Force’s (JGSDF) Araya Maneuver Area, which already hosts Patriot surface-to-air missile systems, is situated in Akita. In January 2019, Japan’s Ministry of Defense had announced that it would conduct a review of the planned Aegis Ashore site’s environmental and health impacts, stemming from concerns from local officials and residents about possible negative effects of electromagnetic radiation from the system’s powerful Long Range Discrimination Radar (LRDR) radar. Japan’s Aegis Ashore sites will use the LRDR in place of the original system’s AN/SPY-1 radar.

Confusion about scale conversions while using Google Earth’s three-dimensional virtual globe function led to officials misinterpreting the angle of elevation of certain mountains by more than 10 degrees in some cases, according to Gomi. The Japanese Ministry of Defense had laid out a requirement to base the two Aegis Ashore systems at sites where there were no obstacles with angles of elevation of more than 10 degrees within a certain distance.

Members of the press watch as trucks associated with Japan Ground Self-Defense Force Patriot surface-to-air missile systems arrive at the Araya Maneuver Area amid a spate of North Korean missile launches in 2009., Kyodo via AP Images

The issue here is the need to provide a good line of sight for the LRDR to be able to detect and track targets in order to cue the Aegis Ashore system’s SM-3 interceptors. If the radar does not have a clear view, it could limit the time available between spotting a threat and engaging it. 

This may become a less significant issue as time goes on. On Dec. 11, 2018, the U.S. military successfully conducted its first ever test of an Aegis Ballistic Missile Defense (BMD) system using the what it calls the “engage-on-remote” concept of operations. What this means is that off-board sensors spotted and tracked the target, then provided fire control quality targeting data to the interceptor launch site. Japan could conceivably network the Aegis Ashore sites in the future together with other radars and sensors, on land and at sea, including those on the Japanese Maritime Self-Defense Force’s Aegis BMD-equipped 27DDG destroyers.

A briefing slide describing various components of the Aegis Ashore system, as well as different engagement options, including targeting threats using off-board sensors., MDA

“We can examine the figures as long as we have map data,” Gomi said in defending the Japanese Defense Ministry’s decision not to conduct physical site surveys of these potential obstacles. “Our checking system was insufficient.”

Despite acknowledging the error, Japanese authorities have no plans to re-evaluate any of the other nine potentially usable sites. Gomi offered no explanation as to why this was the case, according to Japanese newspaper The Mainichi Shimbun. This might come as a shock to local authorities, who already said they had gotten little information about how Araya got selected in the first place.

“After multiple explanations, I was told that, because the Japanese government cannot just use whatever land it wants, negotiations with private landowners weren’t that simple,” Kenta Suzuki, a member the Akita Prefectural Assembly belonging to Japan’s Liberal Democratic Party, which presently control’s the country’s Parliament, had told The Japan Times

in December 2018. “Only national government-owned land, or at least prefectural-owned land, would work, and that’s what I think led to the decision to choose Araya.”

Gomi also did not say whether similar errors had occurred in the decision to locate the second Aegis Ashore site in the JGSDF’s Mutsumi Maneuver Area, which occupies areas within the cities of Hagi and Abu in western Japan. The Japanese government approved the Aegis Ashore plan in December 2017 and the U.S. government approved the planned sale of the necessary components, ancillary items, and associated services, valued at approximately $2.15 billion in total, in January 2019. Japan’s goal is to have both sites operational by 2023 and is no doubt looking to avoid any delays in that schedule.

The U.S. military’s Aegis Ashore missile defense test complex in Kauai, Hawaii. Japan’s Aegis Ashore facilities will be similar, but will notably feature a different radar from the one seen here., Kyodo via AP Images

It’s certainly true that Japan has pushed ahead very quickly with its Aegis Ashore procurement, primarily due to increasing threats from North Korea. Despite a lengthy pause in North Korean missile launches amid a thaw in relations with South Korea and the United States, the regime in Pyongyang has recently restarted testing of short-range ballistic missiles. North Korea also has a long history of test firing missiles and sending them either flying into the East China Sea that separates the two countries or even across Japan’s home islands into the Pacific Ocean.

Aegis Ashore would also give Japan a broader regional ballistic missile defense shield that could help protect outlying areas, including the Senkaku islands, which are at the center of a long-standing and increasingly hostile territorial dispute with China. There is also a possibility that the Aegis Ashore sites could transform into a more offensive ground-based weapon system with the addition of multi-purpose SM-6 missiles or Tomahawk Land Attack Missiles in place of the SM-3s. 

The U.S. government claims that Aegis Ashore is incapable of accepting the Tomahawk, a decision it took to ensure compliance with the now-defunct Intermediate-Range Nuclear Forces Treaty, or INF, with Russia. But Aegis Ashore uses a version of the Mk 41 Vertical Launch System, other variants of which are found on various ships in the U.S. Navy and other navies around the world and can accept these missiles. It remains a matter of contention between U.S. and Russian authorities about how difficult it would be to convert the land-based version to use other missiles beyond the SM-3. A clear offensive capability could also run afoul of Japan’s pacifist constitution, though there has been a growing push in the country to revise Article Nine, which prohibits non-defensive military activities.

A US Navy briefing slide showing the general components found on variants of the Mk 41 Vertical Launch System, including the version that Aegis Ashore employs., USN

Depending on the exact specifications of the LRDR version Japan will use for its Aegis Ashore sites, the radar may also have a secondary intelligence gathering role. China has previously criticized the U.S. military’s deployment of AN/TPY-2 radars associated with the Terminal High Altitude Area Defense (THAAD) ballistic missile defense system to both Japan and South Korea. Chinese authorities have expressed concern that it could be used to spy on activities within its territory, though it is unclear whether the radar has any such capability. 

Whatever the case, the Japanese government seems adamant about establishing a land-based ballistic missile defense layer within the next four years. It remains to be seen whether the calculation error that led to selecting the site in Akita will have any significant impact on those plans by giving additional fuel to existing opposition from local officials or the public. 

But, if nothing else, one imagines that the Japanese Ministry of Defense will make sure to triple check their math when looking at potential locations for any major new military installations in the future.

Contact the author: joe@thedrive.com