The evening test will involve the firing of a target missile from an agency ship at sea and its expected interception by an unarmed anti-ballistic missile from the Pacific Missile Range Facility in Mana, agency spokeswoman Pamela Rogers told reporters during a briefing.

The system is designed to shoot down short - to medium-range ballistic missiles, and could be used by the Army in 2009 or 2010, she said.

"THAAD will protect our soldiers, allies and friendly countries against ballistic missile attacks," she said.

Neither of the test missiles will be armed, Rogers said.

"We want to make sure people don't get the impression we are firing missiles at the island. We are not doing that." she said.

The announcement follows the first THAAD launch off Kaua'i waters in January. Rogers said that operation was successful.

During the upcoming launch, the target missile will "go in a trajectory that is parallel to Kaua'i," she said.

That inert target missile will house a sensor package that will tell tracers where it was when it was hit by the intercepting missile, Rogers said.

PMRF spokesman Tom Clements said the impact will occur at the 'edge of space,' between the Earth's atmosphere and space, and will produce small amounts of debris that will fall into the ocean.

"We have run thousands of computer models to predict when the debris will fall, what size the debris will be," Clements said. "(The idea) is to make sure safety is number one, to make sure we do this in the absolute safest manner possible."

After the test, data will be presented to the Missile Defense Agency to help with developing the best defense system possible, Clements said.

"This is extreme math and science," he said. "This is extreme engineering. The more data you can provide, the better they can determine how well the program is performing."

Lockheed Martin, a systems integrator and information technology company with headquarters in Bethesda, Md., was hired by the U.S. Department of Defense to develop the weapons system, said company spokesman Cheryl Amerine, who will be on hand for the tests.

The defense contractor will test, build and deliver the system to the Army to operate, she said.

Operational THAAD units will be installed at an Army installation in the Mainland and, if needed, can be rapidly deployed to any part of the world, Rogers said.

Testing for the THAAD system was done at the White Sands Missile Range in New Mexico in the1990s, and now has shifted to Kaua'i for the wide-open space available.

THAAD is part of the Missile Defense Agency Ballistic Missile Defense System, which is designed to defend the United States, its deployed troops and its allies.

THAAD complements the Patriot anti-missiles, Rogers said. While the Patriot missiles can defend a small area and can intercept missiles at lower altitudes, THAAD can defend a larger area and intercept enemy missiles at higher altitudes.

"THAAD is the only missile system designed to intercept incoming ballistic missiles either just inside the atmosphere or outside the atmosphere," Rogers said. "The Patriot can hit inside the atmosphere."

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