The failure of an interceptor missile to launch during a December test of the Pentagon's soon-to-be-activated missile defense system was caused by a "minor glitch" in its computer software, and the setback will not delay future testing, a senior official said Wednesday.
It was the first time the booster rocket was to be tested with a new and improved "kill vehicle," the device atop the rocket that uses computer codes and sensors to guide itself into the path of an incoming enemy missile. The device "kills" the target by colliding with it.
Air Force Lt. Gen. Henry A. Obering, director of the Missile Defense Agency, said the Dec. 15 test will be redone in mid-February, and additional tests in April, July and September will proceed as planned.
In the meantime, the eight missile interceptors that are now in underground silos in Alaska and California — while not yet kept ready for use around the clock — are capable of being activated for use against an actual missile attack against the United States, Obering told reporters.
He said he did not know when the system, which links the interceptor missiles with a network of tracking radars and a command post, would be formally declared ready for use. The Bush administration had made it a goal to activate the system by the end of 2004, citing North Korea as the primary threat to launch a ballistic missile capable of reaching the United States.
Obering said his agency plans to have 18 interceptors in silos by the end of this year.
In the Dec. 15 test, a target missile — a simulated ICBM with a mock warhead — was launched without problem from Kodiak, Alaska. But the interceptor that was to fly into the target's path in outer space, destroying it by direct impact, did not launch from its pad at the Ronald Reagan Test Site at Kwajalein Atoll in the central Pacific Ocean.
Offering the first public explanation of what went wrong, Obering said the blame lay with an automated pre-launch check of the communications flow between the interceptor and the main flight control computer. Detecting too many missed messages, the system shut down automatically, as designed.
In response, the Pentagon will increase the pre-launch tolerance for missed messages. Obering said the tolerance level was set too low; increasing it will not risk a flight guidance failure, he said.
"We kind of did this to ourselves," Obering said, by setting the tolerance level so low.
"This has been nothing more than a minor glitch," he added. "Statistically, it's a very rare occurrence and most likely would not happen again."
He disputed the assertion by some outside observers that the failure was a significant setback for a program that has been decades in development at the cost of tens of billions of dollars.
"We're disappointed in the fact that we did not get this (test) off, but we were certainly not embarrassed and we're certainly not disheartened in any way, shape or form," Obering said. "We are working through what we consider to be the fine-tuning of this system."
The target-tracking information that was fed into the interceptor prior to the launch shutdown was checked afterward and determined to be "very accurate" and sufficient to guide the kill vehicle to the target in outer space, he said. "So we were very much encouraged by that."
The missile defense system will initially rely on interceptors based at Fort Greely, Alaska, and Vandenberg Air Force Base, Calif., as well as radars in Alaska, California, at sea aboard ships with Aegis radars and in orbit.