That was the question the United States Air Force wanted to know. After more than five years' worth of collecting and analyzing information on the atmosphere, Air Force officials here have concluded that the atmosphere will not prevent its laser-carrying aircraft, now in development, from doing its job as designed.

That job is using a weapons-class laser, aboard a Boeing 747-400 series freighter aircraft to shoot down theater ballistic missiles of the type used by Iraq during the Gulf War. The atmospheric data collected confirmed that the Airborne Laser, as this 21st century weapon system is called, would be able to fire a laser beam through the atmosphere. As designed, that beam will reach and destroy its targets from hundreds of miles away, shortly after the missiles are launched.

The data was collected by a team from the Air Force Research Laboratory's Directed Energy Directorate and the Airborne Laser System Program Office, both located here. Some of their additional data-gathering over Korea and Southwest Asia was in response to concerns within the Department of Defense that more world-wide information was needed.

According to Maj. Richard Bagnell, a physicist with the laboratory's Directed Energy Directorate, "We used a combination of weather balloons and aircraft, gathering data day and night during all four seasons of the year. This was the first major atmospheric data-collection effort in that part of the world. The information gained will be the genesis of a data base that will continue to grow as we learn more about the structure of the atmosphere."

Also included was an unusual series of tests involving Star Scintillometry. A window was installed, facing forward, on a specially-instrumented flying laboratory called Argus. Through that window, instrumentation locked onto and tracked a star, looking at its scientillation, a technical term for the "twinkling" effect that occurs when the star's light is distorted while passing through the atmosphere. This was another tool for measuring the atmosphere and assessing its effects.

Col. Mike Booen, director of the Airborne Laser office noted, "This dedicated team of scientists and engineers has increased our knowledge of atmospheric characteristics ten-fold. Their findings have validated all of our design criteria with respect to atmospheric effects." He emphasized, "The partnership forged between the lab and the program office illustrates how technologies developed in the laboratory can be applied directly to today's state-of-the-art defense programs."

The Airborne Laser is being built by the Air Force and a team led by Boeing Information Space & Defense Systems of Seattle, Wash. Other team members are Northrop Grumman Space & Electronics of Redondo Beach, Calif., and Lockheed Martin Missiles & Space of Sunnyvale, Calif.

Officials emphasize that the Airborne Laser program is on schedule, leading to a major test in September 2002 for the aircraft to shoot down a theater ballistic missile.