3 December 2001
Beacon Aids Missile Tests More Than Known - Critics
By John M. Donnell
Defense Week

A beacon placed on the target warhead in U.S. anti-missile tests gives the defensive interceptor a helping hand far greater than has previously been disclosed, according to a new scientific report. In several recent tests-- including the one scheduled this past weekend and every one for at least the next year--the target passes its location in flight via a C-band transponder to ground-based computers that then tell the interceptor where to aim. (..)

Pentagon officials have not stated the distance the interceptor had to travel without help from beacon data, despite repeated queries. In a report released Friday, the Union of Concerned Scientists, a group consistently critical of missile defense, says it knows the answer. The beacon data alone was used to place the interceptor just 400 meters from the point where the intercept actually occurred in a successful test on July 14. (..)

The Pentagon has said that the beacon's role will remain the same for the foreseeable future as it was last July.

That means that the beacon alone enables the interceptor to get to within a few football fields of where it needs to be to collide with the target in space- -after the two objects started out approximately 5,000 miles away from each other. Moreover, as a result of only the data from the beacon, the interceptor was placed at a point in space closer to the target than the target was to a decoy balloon and other objects. The kill vehicle is supposed to be able to discriminate the target from decoys, and its job is
easier if it's already been guided closer to the target than the decoys, the scientists said.

At a press briefing Friday, Air Force Lt. Gen. Ronald Kadish, director of the Ballistic Missile Defense Organization, said he did not know what the distance was between the point the beacon got the interceptor to and the point where the target and interceptor actually collided last July. Officials also were unable to provide an answer to the same question at a briefing last August. (..)

Defense officials have said that they must use the beacon to play the role of a proposed X-band test radar in Hawaii that has not yet been built. That X-band radar would detect the target and discriminate it from decoys and the like early enough in the target's flight to provide data for the "weapons task plan," the computer program that aims the interceptor to a point in space as close as possible to where the collision would occur.

In most tests to date, the beacon has stood in for the X-band radar. The beacon sends the target's whereabouts as it flies west from Los Angeles to a small FPQ-14 radar in Hawaii and then on to the battle-management computers to form the initial weapons task plan.

The defense then uses data from a Ground-Based Radar prototype, or GBR-P, in the Marshall Islands, from where the interceptor is launched. The GBR-P provides updates to the initial plan. Then the kill vehicle's own infrared sensors are supposed to seek and destroy the target, about 144 miles up in space last July. If the Union of Concerned Scientists discovery of the 400-meter information is correct, the kill vehicle did not need much more help from the GBR-P or have much space to cover on its own devices. (..)

What little has been officially confirmed about the beacon's role in targeting only came out after "Defense Week" last July revealed the first details about the beacon's role. Military officials still have not confirmed or denied how much the system had to do without the beacon's help. Before August, officials had only said the beacon was needed for safety and telemetry reasons, and they said it had nothing to do with targeting the kill vehicle. That was--strictly speaking--true; but it was largely beside the point. The beacon didn't aim the kill vehicle, but it did aim the rocket that carried the kill vehicle--and that aim was, according to the scientists and other sources, amazingly accurate. (..)