A Maritime Self-Defense Force destroyer equipped with the Aegis air-defense system tracked an H-IIA rocket after launch last month to practice for a North Korean ballistic missile, MSDF sources said Tuesday.

The 7,250-ton Kongou collected aviation data related to the H-IIA rocket, which was launched March 28 from the Tanegashima Space Center in Kagoshima Prefecture, carrying two spy satellites that will monitor North Korean nuclear and missile activities, the sources said.

The destroyer left Sasebo port in Nagasaki Prefecture that day and collected various data until the rocket put the two satellites into orbit, they said.

The drill assumed that North Korea had launched a Taepodong missile, according to the sources. The destroyer collected data for a planned missile defense system being studied by the United States and Japan, they said.

The spy satellite project marks a major turnaround in Japan's space development policy, which was previously based on the principle of peaceful, nonmilitary use of space.

When the rocket was launched, the National Space Development Agency of Japan denied that it had exchanged information with any government ministry, including the Defense Agency.

However, NASDA admitted that the destroyer left port to take part in a joint drill but declined to give any details of the drill.

The Kongou observed the rocket launch from near Tanegashima Island, the sources said. The destroyer had just returned to Sasebo the day before from a patrol in the Sea of Japan.

The sources said the Defense Agency has been collecting data on Japanese rockets for several years.

The Kongou left for the Indian Ocean on April 10 as part of Japan's rear-area support for U.S. military operations there and in Afghanistan.

The government said the information-gathering satellites are intended to bolster