The annual Leonid shower -- this year a storm -- is expected to have an intensity not seen in more than three decades. Even so, the event could provide a dramatic "light show" for some parts of the world, particularly East Asia and the western Pacific region.

The Leonid meteors originate from the debris released from the Comet Tempel-Tuttle which completes an orbit around the Sun every 33 years, leaving a trail of debris such as dust and other tiny particles. The Comet passed perihelion, its closest approach to the Sun, early in 1998, setting the stage for probable meteor storms in 1998 and 1999.

Conditions exist for encountering larger than normal numbers of meteors -- "shooting stars" -- streaking through Earth's upper atmosphere at rates of thousands per hour. Leonid meteors will disintegrate upon entering Earth's atmosphere and pose no threat to aircraft or the Earth's surface.

Leonid meteors travel at about 45 miles per second compared to about 12 miles per second for typical meteors. This risk of physical or electrical damage to near-Earth spacecraft will be greater than normal.

Space operations crews have developed comprehensive strategies to limit the potential effects of the storm. Crews have anomaly resolution procedures in place that are based on years of experience and numerous recovery actions. Several contingency plans exist that deal with specific anomalies for each constellation of spacecraft.

NASA and the U.S. Air Force Space Command will conduct studies of the 1998 Leonid storm and will use these data in forecasting the potential 1999 storm.