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A Flash of Green
September 94. Had you been staring at the sky while the shuttle =
Discovery arched overhead , you might have glimpsed a brilliant green =
flash. Astronauts were peppering Earth with a light-dectection-and =
ranging (lidar) laser, the first to have shone in space.
Lidar works much like radar, except it uses light instead of =
microwave frequencies. Aboard the shuttle, the Lidar In- space =
Technology Experiment (LITE) pulsed in ultraviolet. infrared, and =
visible green wavelenghts, bouncing the beams off clouds and airborne =
particles. Flashing 11 per second, LITE illuminated Earth with circles =
300 yards wide, spaced about half a mile apart because of the shuttle's =
great speed.
A telescope in the cargo bay picked up lidar reflections. From the =
strenght of these echoes, atmospheric scientists gleaned information on =
cloud formations and stratospheric pollution.
While NASA has flown lidars in aircraft since 1980, LITE's =
performance will help engineers judge whether a free-flying lidar =
satellite is warranted. Lidar might also figure into planetary probes.
James Bland, chateaux@tinet.ie
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