President George W. Bush entered the White House in 2001 committed to deploying a missile-defense system "as soon as technologically possible." During his first year in office, Bush decided to withdraw from the 1972 Anti-Ballistic Missile Treaty signed with the Russians 30 years earlier, arguing that it was an impediment to building effective defenses and no longer served U.S. interests in the post-communist world.
A year later he directed the reorganized U.S. Missile Defense Agency to begin deploying national missile defenses by 2004. As a result, the United States now has an operational system of missile-defense sensors and interceptors tied together by a dedicated command network.
The current system, called Ground-based Mid-course Defense -- GMD -- is designed to intercept long-range missiles during the part of their trajectory when they are coasting through space.
Radars and infrared sensors for tracking warheads are deployed in space and at various surface locations around the world, while several dozen high-performance interceptor missiles are deployed at two sites in Alaska and California.
The Missile Defense Agency plans to build out this initial network by gradually adding systems that can attack ballistic missiles of any range in all the phases of their trajectory.
Components of the plan include:
-- The Airborne Laser -- ABL -- and ground-mobile Kinetic Energy Interceptor -- KEI -- for destroying ballistic missiles of any range in the initial boost phase of their flight when they are most vulnerable.
-- The Ground-based Mid-course Defense -- GMD -- and sea-based Aegis Ballistic Missile Defense -- ABMD -- for attacking incoming warheads after boost phase while they are hurtling through space.
-- The ground-mobile Terminal High Altitude Area Defense -- THAAD -- and Patriot Advanced Capability Three -- PAC-3 -- systems for intercepting warheads during the final 30 to 60 seconds of their trajectory, as they re-enter the atmosphere.
The Missile Defense Agency is also funding a global sensor network and command system, plus a variety of other items such as realistic targets for testing defenses and low-cost interceptor concepts.
The final goal is a layered architecture in which ballistic missiles launched against U.S. territory, forces or allies will face several lines of defense that cumulatively thin out or completely eliminate the threat.
The Missile Defense Agency does not expect any particular layer or weapon system to function perfectly.
(Part 6: The benefits of boost-phase interception)
(Loren B. Thompson is chief executive officer of the Lexington Institute, an Arlington, Va.-based think tank that supports democracy and the free market.)
(United Press International's "Outside View" commentaries are written by outside contributors who specialize in a variety of important issues. The views expressed do not necessarily reflect those of United Press International. In the interests of creating an open forum, original submissions are invited.)