The Honolulu Star-Advertiser (http://bit.ly/14XBWAG) reports the $2 billion floating radar component of the U.S. ground-based ballistic missile defense system has left Pearl Harbor for an exercise.

Missile Defense Advocacy Alliance chairman Riki Ellison says an interceptor fired from California's Vandenberg Air Force Base will try to shoot down a target missile fired from Kwajalein Atoll.

The Missile Defense Agency doesn't release a test date until it has issued a "Notice to Airmen and Mariners." The notice had not been issued Tuesday.

Four interceptors are in silos at Vandenberg and 26 others are at Fort Greely, Alaska.

The system is an element designed to protect Hawaii and the mainland from missiles fired from locations such as North Korea.