ON SEPTEMBER 1, 2006, a handful of uniformed U.S. service members and Congressional staffers gathered in a windowless room in the headquarters of the Missile Defense Agency, tucked within a row of nondescript buildings on a low hill overlooking the Pentagon. The guests waited anxiously in the room, called the Management Information Center, watching several large computer displays on the wall in front of them.

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They were about to find out whether the Missile Defense Agency could stop an intercontinental ballistic missile by shooting it down with an interceptor missile. This would be the first test of an interceptor launched as though the country were responding to an actual attack on its homeland. Previous interceptors were fired from Kwajalein Atoll in the Pacific Ocean; this one was to be launched from California.

The target rocket had been fired by U.S. forces on Kodiak Island, Alaska. On the screens in the Management Information Center, a red line, progressing southward from Alaska toward the west coast of the United States, represented its position. The target missile’s path was similar to the trajectory that a Taep’o-dong 2 long-range missile launched from North Korea might follow. The difference, of course, was that if the September test failed, the Kodiak-launched target would splash down harmlessly off the Baja peninsula.

The anti-missile system that is, by the order of President George W. Bush, being fielded as it is developed, is a complex web of layered defenses, each aiming at a separate missile threat. Some are meant to thwart missiles as they rise from the pad (the pre-boost phase), while others are designed to destroy them as they descend toward the target (the terminal phase). The flight time between the two phases is called the “midcourse.” Midcourse defenses are the only ones currently fielded against long-range threats, like ICBMs.

The focal point of the agency’s September test of its Groundbased Midcourse Defense system was the interceptor missile, launched from Vandenberg Air Force Base in California. According to plan, it would rise out of Earth’s atmosphere and release an infrared-seeking projectile called a “kill vehicle” that would collide with the target somewhere over the Pacific.

Watching the red line’s progression across the screen in the information center, Air Force Lieutenant General Henry “Trey” Obering, director of the Missile Defense Agency, had something to prove besides the capability of hitting a bullet with a bullet.

Obering, who had spent seven years helping NASA launch space shuttles, compares the feelings surrounding a missile test to the emotions evoked by a shuttle launch: “It was kind of scary, because with all the models and simulations, you just didn’t know exactly what was going to happen until it did.”

With this test, his agency was attempting to redeem itself for a series of failures that had called its competence into question. The lack of midcourse interceptions in the MDA program also suggested that that the technology was not mature enough to handle the task.

Since they were initiated in 1997, midcourse defense test flights have had mixed results. Between October 1999 and July 2001, three of five intercept tests had ended in success. But there had been a four-year lull in midcourse intercept launches, and only failure when they restarted.

The last time the missiles flew, in December 2002, the kill vehicle did not separate from the interceptor that carried it. Two years of work followed, during which Obering took over the Missile Defense Agency. Engineers from Raytheon Company cleaned up the design and began production of the kill vehicles at their Tucson, Arizona facility.