Word: pioneer
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Cruising through the cosmos at 27,700 m.p.h., the Energizer bunny of NASA spacecraft is measuring cosmic rays and solar emissions, probing for the outer boundary of the solar system and even abetting the efforts of scientists pursuing SETI, the Search for Extraterrestrial Intelligence. When Pioneer was launched in March 1972, its primary assignment, ordained by NASA, was to reach the environment of Jupiter. At the time, says physicist James Van Allen, the discoverer of Earth's radiation belt and a principal contributor to Pioneer's achievements, "this objective was regarded as a bold one." While unmanned U.S. and Soviet...
...swung by Jupiter in November 1973, Pioneer took the first close-up photographs of the giant planet and its moons, detected and mapped its immense magnetic field and intense radiation belts, analyzed its turbulent atmosphere and discovered that it was encircled by a faint Saturn-like ring...
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...