Word: pioneers
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Dates: during 1990-1999
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Then, assisted by a powerful boost from Jovian gravity, the spacecraft hurtled toward deep space. Not far beyond Jupiter, scientists had expected Pioneer to find the boundary of the heliosphere, beyond which the solar wind (charged particles emitted from the sun) can no longer be detected. Yet as distant as Pioneer is today, it is still being wafted by solar breezes, and scientists now believe the elusive boundary could lie as far as 10 billion miles from the sun, and perhaps farther...
...Pioneer will eventually cross that boundary but will be unable to convey the news to Earth. Unlike spacecraft operating closer to the sun, it cannot rely on solar panels to generate power. Instead it is equipped with a thermocouple-like generator heated by radiation from a clump of plutonium 238. Unfortunately, the radiation is also slowly degrading the generator, which is producing only two-thirds of its original output...
Last week in the Pioneer control room at NASA's Ames Research Center, in Mountain View, California, project manager Fred Wirth watched Pioneer's data, in the form of multicolored blocks of numbers flashing across a computer screen. To make the best use of the spacecraft's dwindling power, he has shut down all but three of its 11 scientific instruments, and by early next year only one--Van Allen's cosmic ray detector--will be able to function. Citing operational costs and the diminishing scientific return, NASA has ordered Wirth to halt all communications with Pioneer next year...
That is melancholy news not only for Wirth and other members of the Pioneer team but also for astronomer Frank Drake and his crew at the nearby Mountain View headquarters of seti. There, scientists hoping to pick up radio signals from a distant civilization have been using Pioneer's signals to test the efficacy of their detection systems. Says Drake: "It's been our prime diagnostic tool...
...even a silent Pioneer 10 may someday effect a kind of communication with extraterrestrials. Attached to one of the spacecraft's antenna support struts is a plaque, designed by Drake and astronomer Carl Sagan, that is inscribed with symbols, binary numbers and drawings conveying what they hope is a universally understandable message. It locates the solar system, shows that Pioneer was launched from Earth and portrays a terrestrial man and woman...