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The (1) Ulysses solar probe, after 17 years of studying the sun and solar system, is about to die by freezing to death, NASA and the European Space Agency said.
The satellite had long outlasted the five-year mission it began in 1990, but it continued to transmit useful data on solar winds.
More recently, its plutonium power source had slowly weakened and its fuel was freezing as the probe made a wide circle of the sun,traveling as far as Jupiter.
In January, engineers tried a longshot maneuver to heat up the fuel. Instead, their effort backfired and hastened Ulysses' death by several months.
"It was rather uncertain it would work; it's so harsh and cold out there," Arik Posner, NASA's Ulysses program scientist said. "It was our only option." Had it worked, engineers figured they would have gotten an extra two years of life from Ulysses. The final transmitter will probably quit in the next few weeks, according to the European Space Agency.
The $250 million (euro 168 million) probe was a joint European-NASA project. After being released from orbit by astronauts on the space shuttle Discovery in October 1990, Ulysses made nearly three full wide circles of the sun from above and below its poles. It also circled over Jupiter's poles, logging about 6 billion miles (nearly 10 billion kilometers) overall.
What made Ulysses unique and crucial to scientists was its orbit and perspective. It provided astronomers with a three-dimensional look at the sun and the rest of the solar system. Most of the planets line up along the same geometric plane generally around the middle of the sun and that is where most of the space probes orbit, too.
But Ulysses made long wide circles of the sun's poles, essentially gazing down at the sun and solar system from above and below instead of around the middle. ■AP
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