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A test above the Pacific Ocean early this month was characterized by a Pentagon official as a “huge step” in proving technologies to intercept long-range ballistic missiles, such as ones North Korea is developing. But some expert observers say it was unremarkable because it largely reiterated earlier achievements and did not–unlike some earlier tests–attempt to overcome potential counter-measures that an enemy could deploy. What’s more, critics have expressed dismay about the classification of the test data, which makes it impossible to conduct an independent evaluation.

In the September 1 test, an interceptor launched from California’s Vandenberg Air Force Base struck a mock warhead fired from Kodiak, Alaska. Similar tests in December 2004 and February 2005 had failed, prompting the U.S. Missile Defense Agency to suspend tests. But in this test, the interceptor hit the target, the agency said. The recent test also included a successful performance of radar-tracking and command elements, according to the agency, and was the first test-firing from the mainland United States. Previous interceptors had been fired from an atoll in the Marshall Islands.

“Basically, what we did today is a huge step in terms of our systematic approach to continuing to field, continuing to deploy, and continuing to develop a missile defense system for the United States, for our allies, our friends, our deployed forces around the world,” said the director of the missile agency, Lt. Gen Henry “Trey” Obering, when announcing the results on September 1. If North Korea tried to fire a missile at the United States, he said, “we’d have a good chance” of shooting it down with existing technology.

The agency’s ultimate goal is to deploy a “layered” defense that could stop all ranges of missiles, from short to intercontinental, in all phases of a missile’s flight. The September 1 test was of ground-based systems that fire upon long-range missiles in their mid-course phase. Since the mid-1980s, the United States has spent more than $90 billion to develop missile-defense systems, and currently has a limited deployment of some pieces.

But critics argue that the recent test didn’t address a potential Achilles Heel of long-range missile defense: how to differentiate a warhead from decoys that might be flying alongside it in the near-vacuum above the atmosphere.

“The issue has always been whether it can deal with countermeasures, and the issue most talked about is decoys,” says George Lewis, a physicist at Cornell University. He notes that earlier tests tried to deal with decoys. “If you look at the progression: the first two tests [in the late 1990s] were not interception tests but had fairly sophisticated decoys, then we had the test where we were shooting at the warhead, plus a spherical balloon. Now we don’t have any decoy. If anything, it looks like we are going backwards.”

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