This ability is derived from the Aegis combat system and the latest version of the Standard Missile, the SM-3. The recent successful sea-based ballistic missile defense (BMD) test that involved the Japanese Maritime Self-Defense Force signals a dramatic new capability for Japan while affirming a significant commitment from Japan to defend against this growing threat.

Japan was the first allied nation to acquire the sophisticated Aegis combat system, with the introduction of the Kongo-class guided-missile destroyer to its fleet. The U.S. Congress approved the Aegis sale to Japan 20 years ago. Now, Japan has become the second nation to obtain a sea-based BMD capability, as the destroyer Kongo, with its Aegis system modified for BMD, detected and engaged a ballistic missile target launched from Pacific Missile Range Facility on Kauai, Hawaii, in December.

Kongo's Aegis system tracked the target, developed a fire-control solution and launched an SM-3 equipped with a Lightweight Exo-Atmospheric Projectile (LEAP) kinetic warhead. About three minutes later, the missile intercepted the target in the exoatmosphere at an altitude of more than 100 miles above the Pacific Ocean.

Although the Kongo is not a new ship – it entered service in 1993 – its new capability makes it a much more formidable asset.

“Japan had the forethought to build the multimission Kongo-class with enough margin so that after 15 years of service, it could be upgraded for a whole new mission,” said Rear Adm. Brad Hicks, who heads up the Aegis BMD Program Office within the Missile Defense Agency.

Kongo retains its multimission capability, including anti-submarine and anti-aircraft capabilities.

“It is a real tribute to the Aegis combat system that we are able to upgrade it with an entirely new capability,” Hicks said.

The ability to counter medium- and long-range ballistic missiles is becoming more important as more countries acquire them.

“Lots of nations have expressed an interest in acquiring a ballistic missile defense capability,” Hicks said. “We have agreements in place with a number of nations to discuss the technical requirements of achieving a BMD capability. Only one nation has come forward and actually acquired the capability, and that is Japan.”

The event, designated Japan Flight Test Mission-1 but nicknamed “Stellar Kiji” – kiji is a Japanese pheasant – marked the first time that a non-U.S. naval ship intercepted a ballistic missile target with the sea-based mid-course engagement capability provided by the Aegis BMD system.

Other allied navies have participated in Aegis BMD tests, but their roles were limited to surveillance and tracking.

“Today's test further proved that the evolving Japan-U.S. alliance is the indispensable foundation of not only Japan's security, but also for the maintenance of peace and security in the Far East,” said Akinori Eto, Japan's senior vice minister for defense.

The Kongo, he said, “now an Aegis BMD-capable destroyer, with the help of the SM-3 missiles, will provide protection to the people in Japan from the ballistic missile threat in the region, which will certainly enhance the security of Japan by providing a reliable defense asset and deterrent in the region.”

With a displacement of 9,485 tons and a length of 528 feet, the Kongo is slightly larger than the U.S. Navy's Arleigh Burke-class destroyers.

The original Kongo class comprises four ships equipped with the Aegis combat system. The newest of these entered service in 1998. Japan plans to modernize all four, at a rate of one ship per year, to the BMD standard.

Beyond the first four ships of the class, Japan is adding two improved Kongo-class DDGs. The first, Atago, was commissioned last year and called at Pearl Harbor, Hawaii, at the same time Kongo was participating in Stellar Kiji.

The second, Ashigara, will join the fleet next year.

North Korea launched a Taepodong 1 ballistic missile over Japan in August 1998. The missile landed in the Pacific Ocean about 1,000 miles from the launch site.

“We see this as a very dangerous act,” a Japanese government official said after the 1998 incident. “It will have a serious impact on the security of Northeast Asia.”

Today, North Korea is said to be developing a long-range ballistic missile capable of reaching Guam.

Such growing threats have spurred continued development of countermeasures, such as the SM-3.

“The SM-3 is a four-stage missile, so it's a lot bigger than the SM-2,” Hicks said. “The SM-3 first stage gets the missile off the ship, and then the second stage kicks in, which gets it to the edge of the atmosphere. The third stage gets it into space, and the fourth stage is the kill vehicle, which intercepts the target and destroys it with its kinetic energy.”

The infrared-guided warhead travels at about 2.7 kilometers per second at the time of intercept.

The SM-3 first flew in 1999, and its first intercept was made in 2002. With the Stellar Kiji test, the Aegis BMD system has made 12 intercepts in 14 attempts. The latest success for the SM-3 occurred Feb. 20, when the Aegis cruiser Lake Erie shot down a crippled U.S. spy satellite.

Planning for the $55 million Stellar Kiji test took about a year. When Kongo returned to Japan, it carried a number of SM-3 missiles in its magazine and now is able to provide an operational BMD capability to the region. The December launch was the first in a series of live-fire tests that will exercise Japan's ability to launch interceptors and defeat missiles that accurately mimic capabilities of ballistic missiles fielded by other nations.

Rear Adm. Joe Horn, a former commanding officer of the Lake Erie and the Navy's current director of surface combat systems, said “Kongo's accomplishment demonstrates that now both America and Japan are successfully providing the best tools possible to defend their respective nations.”

The unique success of the Navy's sea-based BMD capability figures prominently in the sea service's shipbuilding and modernization plans. With Missile Defense Agency funding, the Navy is equipping 15 guided-missile destroyers and three guided-missile cruisers for BMD by 2009. Although most of these ships are based in the Pacific, the capability also will be installed on Atlantic Fleet ships, with Norfolk, Va.-based destroyer Ramage now BMD- capable.

All of the Arleigh Burke-class destroyers eventually will be BMD capable, and the Navy is looking to fund upgrades for all of its 22 Aegis guided-missile cruisers.

“The investment to upgrade an Aegis surface combatant to the BMD capability over the 40-year service life of the ship is less than a decimal point. It's in the noise. Yet it's a huge increase in capability,” Hicks said. “There are some launcher modifications and upgrades to the computer, and there are some adjunct computers that are required. It costs about $30 million to upgrade a ship, and the SM-3 missiles cost about $10 million each. That's very reasonable when you consider the capability the combined ship's weapons system and the missile provide.”

Aside from Japan, Hicks said, other U.S.-allied nations are on the verge of BMD capability.

“The Spanish Aegis frigate Mendez Nunez, has been out here … and successfully tracked a target,” Hicks said. “We believe they'll acquire the long-range search and track capability because they want to participate in collective defense.”

Lake Erie has participated in nearly every live-fire event of the Aegis BMD capability and can rightfully claim to be the pre-eminent BMD warship in the world. Lake Erie and Kongo participated in the November test, in which two ballistic missile targets were intercepted by two SM-3s. Lake Erie engaged the targets independently, and Kongo took advantage of the test to prove its tracking capabilities.

“We're taking the BMD capability from the demonstration stage to being a core capability of the U.S. Navy,” said Lt. Cmdr. Drew Bates, combat systems officer on the Lake Erie. He has participated in six firing missions so far. “Each one is different,” Bates said. “Each one has built upon the others. There's been no treading water. There has been progress with each exercise.”

“We learn a tremendous amount every time we do this,” said Capt. Randy Hendrickson, Lake Erie's commanding officer.

“The Navy and MDA are leveraging the existing Aegis and Standard Missile technology and are growing it, stressing it and getting it to do things that it was not originally designed to do. Aegis missile defense is a powerful tool the Navy brings to the joint fight.”

Retired U.S. Navy Capt. Edward Lundquistis a senior science adviser for Alion Science and Technology.