Missile Test Off by 6 Seconds, Data Show

The missile interceptor that failed a critical flight test over the Pacific Ocean apparently missed its target because of the failure of two heat-detecting sensors six seconds before the intended “kill,” defense officials said Wednesday.

Although other important parts of Tuesday’s flight test apparently took place as planned, the sensor glitch meant that the 120-pound “kill vehicle” failed to make a last-minute maneuver that would have put it directly in the path of the mock warhead, causing a pulverizing 15,000-mile-per-hour collision.

The test was one of only two remaining before President Clinton is to decide whether to deploy a $12.7-billion national missile shield aimed at protecting the country from attacks by “rogue” nations such as North Korea or Iran.

The failure increases the odds that Pentagon officials will not judge the system ready and that Clinton will decide against deployment or leave a decision to his successor.

Pentagon officials have drawn plans for a system with 100 missile interceptors, probably based in Alaska, designed to shield all 50 states from an attack involving a handful of incoming ballistic missiles. The system, if deployed, could be in place as early as 2005.

But the proposal remains hotly controversial. Critics say that it would not be reliable and could jeopardize the global balance of power and undermine arms control treaties that are better safeguards. Leaders in Russia, China and many European countries, who fear a change that would bring instability, have complained about U.S. plans to develop the missile shield.

Supporters of the missile defense program, the successor to Ronald Reagan’s “Star Wars” initiative, said that the test flight failure would not doom the program. “This is not a setback by any means,” said Rep. Curt Weldon (R-Pa.), chairman of the House Armed Services research and development subcommittee. “We need to move forward with the deployment to protect American families from missile attack.”

Defense officials, while acknowledging their disappointment, nonetheless tried to emphasize the bright spots in the test results as they narrated an account of the 30-minute flight.

The test flight, the fourth in a series of 19, was set up so that a mock warhead atop a missile launched from Vandenberg Air Force Base at 6:19 p.m. PST would be smashed a half hour later by an interceptor shot from the Army’s Kwajalein Atoll missile range in the Marshall Islands.

Just as planned, the “enemy” missile from the California air base was spotted and tracked by the defense system’s satellites and ground radars.

The interceptor missile was launched 20 minutes later. The kill vehicle separated from its rocket as planned and, hurtling through space at 5,000 miles per hour, adjusted its trajectory twice, officials said.

With the planned collision three minutes away, the craft took its first look at the target and saw it “nearly dead center,” said one defense official, who briefed reporters at the Pentagon on condition of anonymity.

Another electro-optical sensor also picked up the target and was able to distinguish it from a decoy balloon that was flying nearby.

But with the collision only six seconds away--and the two objects only 12.5 miles apart--the two heat-detecting sensors failed to take a last crucial look at the target, and the kill vehicle whizzed by it.

The missile defense team members were hoping to see a bright flash of light from the collision as they did in October when their kill vehicle smashed its target 120 miles in space.

The infrared sensors, which help guide the craft and enable it to pick out targets, are part of the kill vehicle’s most sophisticated system. Defense officials did not speculate about what might have caused the sensors to malfunction but outside experts said that the failure could have several causes.

There may have been a failure of electrical power or coolant systems or of the software that enables the system to discriminate between objects in space.

As with the rest of the missile defense system, “there are so many things that could go wrong, and everything has to go right,” said John Pike, an analyst with the Federation of American Scientists in Washington.

Defense officials stressed that their analysis, derived from data sent back from space, is preliminary and may be changed after more information is analyzed. They acknowledged it is possible that they may find other glitches.

Data from the tracking satellite brought the interceptor within a state-sized area of outer space, the defense official said, while ground-based early-warning radar brought it “within the right ZIP Code,” and a prototype of a sophisticated X-band radar “got us to the street address.”

“What we failed to do was ring the doorbell,” he said.

Defense officials have said that they could not recommend deployment unless they have two successes in the final three tests. That means that the kill vehicle must strike its target in the next test, scheduled for late April or May.