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.”

The fundamental achievement–hitting the equivalent of a long-range ballistic missile–is not itself new. “It’s not that remarkable. We first hit an object in space with an interceptor more than 20 years ago,” says Lewis. “Basically, this is the kind of test that will always work unless something goes wrong. There was no principle being tested here. We know we can hit a warhead with an interceptor. We’ve done it.”

Philip Coyle, an assistant secretary of defense in President Clinton’s administration and now an adviser to Washington think tank the Center for Defense Information adds that “this test was simpler than any flight test conducted so far in this program.”

But a missile agency official takes issue with that characterization. “This test was incredibly complex. It was absolutely the most complex one we have ever tried. Everything had to come together, and it did. The critics certainly have to realize how complex this undertaking… was,” says Rick Lehner, the agency’s chief spokesman. “It was the first operational launch from Vandenberg, with operational vehicles, the first operational command and control system in Colorado Springs, with upgraded radar to develop the firing solution.” Lehner adds that “Each time, [tests] show an improvement in the interceptor technology itself. It’s an evolving process to make it better. There is nothing simple about it at all.”

The agency says the test was representative of a real missile fired from North Korea, including the basic trajectory and propulsion that such a missile would use.

But, since no data has been released, it’s not possible to evaluate how realistic the test was, says David Wright, a physicist and co-director of the Global Security Program at the Union of Concerned Scientists in Cambridge, MA. “A few years ago [the agency] started classifying all the information about the tests, so there is less information available than there used to be,” he says. “You see them claiming how this was so realistic, how this was simulating a North Korean target. Now there is virtually no way to balance what they say. There are no details about what the nature of the target was.”

The next test is set for December, and, while no decision has been made, it might include decoys or other measures meant to confuse the interceptor, according to the missile agency.