Publicly, President Obama and senior officials in his administration berated North Korean leader Kim Jong Il last week for firing 11 ballistic missiles eastward into the Sea of Japan, four short-range missiles on July 2 and seven medium-range missiles on July 4. It was the biggest North Korean missile barrage seen so far.

Secretly, U.S. officials informed on missile defenses were pleased, for two reasons. First, the elaborate U.S. missile defense in place in Japan, Alaska, California, Hawai'i, aboard Navy ships and in satellites was severely tested and worked well. In particular, the fusion of data from sensors based on land, at sea and in space produced swift and clear images of what the missiles were doing.

Second, U.S. intelligence gathered information about the missiles that otherwise could not have been had. An official in Washington said: "We learned an incredible amount about where exactly North Korea is in their long-range missile development program." Because North Korea has only aging radar, he doubted that North Korea "learned anything close to what we learned about their tests."

The officials said North Korea's missiles were fired from mobile launchers, but the U.S. had been able to track them with satellites and reconnaissance aircraft. U-2 surveillance planes flying outside of North Korean airspace, for instance, transmitted digital photographs to be fed into the fused data.

In addition, the North Koreans have become more skilled at disguising launch sites with shields like medieval armor through which radar cannot see. The U.S., however, has found undisclosed ways of piercing that camouflage. U.S. sensors were able to pick up North Korean missiles when they had flight times of only 2 to 11 seconds, indicating either a failed launch or a target close to the launch point.

The missiles were sighted by U.S. radar in northwestern Japan near the remote village of Shariki, then picked up by radar on Shemya in the Aleutian chain of Alaska and another encased in what looks like a giant golf ball aboard a seagoing base in the mid-Pacific. A satellite and an Aegis destroyer on patrol in the Pacific also tracked the missiles.

Missile data were transmitted to a U.S. command center at Yokota Air Base west of Tokyo, where much was shared with Japan's Self-Defense Forces. The data went to operations centers in Hawai'i, Northern Command in Colorado, Strategic Command in Nebraska, the National Military Command Center in the Pentagon, and to the situation room in the White House.

Keeping track of the missiles was made a bit easier when the North Koreans spaced out the launches. Joseph Bermudez, a specialist on North Korean military affairs, wrote in Jane's Intelligence Review that on July 2, the launches of the missiles were 40 minutes to nearly two hours apart. They landed in the sea within 60 miles of shore.

On July 4, the seven missiles were launched, mostly about two hours apart. The trajectories were generally northeast into the Sea of Japan after flights of 270 to 300 miles. All suggested that the North Koreans had improved the accuracy of their missiles.

The only aspect of missile defense not tested was, obviously, taking a shot at a North Korean missile. The system was alerted to shoot if the sensors had shown a long-range missile headed to a target in Japan or the U.S., including Alaska and Hawai'i.

Had Obama given the order to shoot, computers in a fire-control suite in Alaska would have selected interceptors in Alaska, California, or aboard an Aegis ship at sea to shoot at the missiles while in mid-course. As a last resort, an anti-missile missile would have been fired from Hawai'i at the incoming warhead hurtling down from space.

Richard Halloran, formerly a New York Times correspondent in Asia and in Washington, is a writer in Honolulu.