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June 24, 1999 |
The noise turned out to be not E.T., but the Solar and Heliospheric Observatory (SOHO), phoning home to NASA from a million miles away. The research satellite is designed to study the internal structure of the sun and the solar wind, a stream of highly ionized gas that blows continuously outward through the solar system. SOHO orbits the sun just ahead of the Earth and beams back data using radio waves. Still, the episode did more than get astronomers' hearts racing; it presaged the noisy near future. Of the thousands of satellites in orbit, those dedicated to scientific research are relatively few. But the number of telecommunications satellites is exploding. Led by the Iridium satellite telephone network, these high-altitude "birds" are nearly always buzzing overhead, creating what one astronomer calls a "dial tone in the sky." Click here to check out the latest Technology books at BARNES & NOBLE
As they send signals to Earth, the satellites are confined to frequencies just outside the ones reserved for radio astronomers to study celestial events too distant to be seen by optical telescopes. But these satellite transmissions are imprecise. They tend to bleed over into other frequencies like unkempt shrubbery; scientists call them names like "spurious" and "out-of-band." For centuries astronomers studied only the visible portion of the electromagnetic spectrum. But many cosmic phenomena emit more strongly at radio wavelengths than at those of light -- a discovery made by a Bell Labs engineer in 1932. Since then, the radio telescope has provided countless previously unavailable clues about the universe. In just the last six months, radio astronomy has advanced scientific knowledge about evolving planetary systems and black holes lurking at the hearts of most galaxies. SETI scientists also rely largely on radio telescopes in their quest to find the transmissions of alien life. But space noise is becoming a potent threat to this relatively young branch of astronomy, making the operation of a radio telescope these days a bit like aiming a flashlight at a star from amidst the flash and neon of Times Square.
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