The Self-Defense Forces have begun deploying units after receiving an order from Defense Minister Naoki Tanaka to intercept a North Korean ballistic missile if necessary, with the aim of preventing the missile or its fragments from falling within Japanese territory. To do so, the SDF will carefully detect and track the missile, which North Korea calls a satellite.
On Thursday, a day before the order was issued, Gen. Shigeru Iwasaki, chief of staff for the SDF Joint Staff, said the SDF will be fully prepared to protect lives and the nation's property.
The SDF will deploy surface-to-air Patriot Advanced Capability-3 (PAC-3) missiles at seven locations in Okinawa Prefecture and the Tokyo metropolitan area. It will also deploy three Aegis-equipped destroyers.
The SDF further plans to use ground-based radar and deploy aircraft capable of collecting radio wave information in preparation for the launch.
According to sources, an initial report of the North Korean launch will be given by US forces after an early warning surveillance satellite detects a heat source at the time of the launch.
The information will be sent instantly from the North American Aerospace Defense Command in Colorado to the Air Self-Defense Force's Air Defense Command at the U.S. Yokota Air Base in Tokyo and the ministry's Central Command Post via various places, including the U.S. military forces headquarters in Japan at the Yokota Air Base.
The missile will then be tracked by the ASDF's Fixed Position System-5 (FPS-5) warning and control radars. The radars will emit radio waves in the direction the missile is expected to emerge over the horizon.
FPS-5 radars on Sado Island in Niigata Prefecture, Shimokoshikijima island in Kagoshima Prefecture and Mt. Yozadake in Okinawa Prefecture are expected to play an important role.
The missile will be detected by the EPS-5 on Sado Island immediately after its launch, and will be tracked by the radar on Shimokoshikijima island. Afterward, the tracking will continue to the east of the Philippines by the EPS-5 at Mt. Yozadake.
The SPY-1 radar, which reportedly has a range superior to that of the more than 1,000-kilometer range of Aegis-equipped destroyers, will also track the missile.
Relevant information collected by Japan and the United States will be compiled at the Air Defense Command and the Central Command Post with the missile's trajectory and expected landing spot shown onscreen.
The chief of the Air Defense Command will decide whether the missile should be intercepted if it appears likely to fall within Japanese territory.
A senior ministry official said there should be no problem in tracking the missile since the expected launch time and location are already known.
Interception will be unnecessary if the missile follows the initially reported route since it will pass about 500 kilometers above the area around Ishigakijima island.
However, interception will be necessary if the missile becomes likely to fall on Japanese land or water due to inadequate thrust or failure to detach from a rocket booster.
If the Aegis-based Standard Missile-3 (SM-3) system fails to intercept the missile outside the earth's atmosphere, PAC-3 missiles will be used at a height of more than 10 kilometers above the earth.
What matters is the reliability of SM-3 and PAC-3 missiles. "SM-3 will be enough to intercept a North Korean missile if it falls within Japanese territory because of inadequate thrust," said missile expert Hideaki Kaneda, a former official of the Maritime Self-Defense Force and director of the Okazaki Institute.
Japan and the United States have conducted successful interceptions in 18 out of 22 SM-3 live-fire tests. Japan used Aegis-equipped destroyers in four tests, and failed in one test because of warhead guidance system trouble.
Interception plans will change in the event missile parts or fragments fall. Aegis-equipped destroyers and PAC-3s are designed to track warheads with their radars.
It is possible for PAC-3s to set their radars for different parts. However, these parts and fragments will move irregularly due to air resistance.
A senior ASDF official said, however, PAC-3s will be able to respond to such irregular movement as they are built based on technology used to shoot down aircraft.
The SDF's interception units and radar have been enhanced since the time of the missile launch by North Korea in April 2009.
This time, the ballistic missile defense system, on which the government has spent a great deal, will be put to the test.