Tonight, a thin beam of light will flash down from outer space to illuminate dark parts of North America, Europe and Asia if a Russian space test succeeds and if clouds don't get in the way. Astronomers are protesting the experiment, saying such developments threaten to produce new kinds of light pollution that could blind telescopes exploring the night sky. In the test, astronauts aboard the Russian space station Mir are to bounce sunlight off an 82 foot mirror and direct the rays toward the ground, producing beams up to 10 times brighter than the full moon.