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Plutonium-Powered Satellite to Probe Sun’s Poles

June 26, 1990

CAPE CANAVERAL, Fla. (AP) _ A plutonium-powered satellite that will be launched from the shuttle Discovery this fall to explore the sun’s poles poses little health risk in the event of an accident, space officials said Tuesday.

″We have looked at the statistics ... and our conclusion is that we think it’s definitely as safe as it can be and we’re not worried about it,″ said astronaut Thomas Akers, who will be part of Discovery’s five-man crew.

Ulysses’ scientific instruments will be powered by one radioisotope thermoelectric generator (RTG), which converts heat from decaying plutonium into electricity. Two such generators were aboard the Galileo spacecraft that was sent on a six-year journey to Jupiter from the shuttle Atlantis last October.

Environmentalists had opposed Galileo’s power supply. They said a Challenger-like accident could scatter the deadly plutonium over Florida. But Willis Meeks, Ulysses project manager for NASA, said at a news conference the chances of that happening were ″very small.″

In the likelihood of the worst possible disaster, in which plutonium was released into the atmosphere, Meeks said there would be an additional 300 to 400 cancer deaths over 50 years based on the world’s entire population. But a U.S. Energy Department engineer at the briefing who refused to identify himself said that estimate was much too high.

President Bush is expected to approve Ulysses’ launch in early September. Presidential approval is necessary when RTGs are used.

The approximately $750 million mission is on schedule for an Oct. 5 launch, said John Conway, director of payload management and operations for the National Aeronautics and Space Administration. There is no evidence of any damage to Discovery’s right payload bay door, which inadvertently was yanked upward earlier this month by an overhead bridge, he said.

Ulysses will be the first spacecraft to orbit over the sun’s poles, providing new insight into solar winds and magnetic fields, said Peter Wenzel, Ulysses project scientist for the European Space Agency. The European agency is splitting the cost and responsibility of the mission with NASA.

Wenzel said it will be like seeing the sun in the third dimension.

″Think of some little green man from Mars who comes, lands near the equator, looks around, goes back and describes what the Earth is like. That’s not the whole story. You have to look at all latitudes,″ Wenzel said.

Discovery has until Oct. 23 to lift off with Ulysses because of the alignment of Earth, the sun and Jupiter, whose gravitational field will slingshot the satellite back to the sun. Otherwise, the flight must be delayed for 13 months, said Willis Meeks, Ulysses project manager for NASA.

It will take Ulysses 16 months to reach Jupiter and 2 1/2 more years to reach the sun’s 70-degree south latitude. In mid-1995, the satellite is expected to be in the same spot on the northern side.

The 814-pound satellite will not be any closer to the sun during the five- year mission than it is now on Earth - a distance of 93 million miles. It will be twice that far, in fact, when it passes over the solar poles.

Ulysses is named after the heroic adventurer in Greek mythology.

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