Weather Interferes With Space Shuttle Experiments

Astronauts aboard the space shuttle Discovery on Thursday tried out an Army laser receiver and a new camera system designed by the Navy, but poor weather conditions hampered their efforts.

The five military crew members began work on the unclassified portion of their weeklong mission after successfully releasing a spy satellite for the Pentagon on Wednesday. The laser receiver and camera are intended to eventually assist in warfare.

In the first shuttle experiment of its kind, military laser experts on the ground beamed green laser pulses at Discovery as it passed overhead. But cloudy skies over the laser station at Kirtland Air Force Base in Albuquerque prevented signals from reaching the receiver mounted in one of the shuttle’s windows. The second test could not be performed because of rain at Ft. Huachuca in Arizona, another laser-sending site.

The Army wants to see how well lasers can send information for its Global Positioning System. Sixteen advanced Navstar Global Positioning System satellites are in orbit; the 16th was launched 2 1/2 weeks ago.

During the Persian Gulf War, U.S. forces relied heavily on Navstars, which can tell receiver-equipped soldiers where they are within 50 feet.

Using lasers to transmit such information rather than radio frequencies would be more secure and consequently safer for downed pilots or stranded soldiers, said Lt. Col. Jan Drabczuk of the Army Space Command.

Preparing for another experiment, the astronauts lowered Discovery’s altitude from 230 miles to 201 miles for the release today of six metal balls between two inches and six inches in diameter. NASA does not want to eject the balls into the same orbit as the newly deployed spy satellite because of the possibility of a collision.

Space debris researchers will track the orbiting balls with radar and telescopes to calibrate the instruments and to improve small-object observations.

Discovery, scheduled to land here Wednesday, was off the ground less than 24 hours when NASA workers began moving the shuttle Endeavour out for its January launch.