December 12, 1997 in Nation/World

Soon, Pioneer Won’t Call Home Space Voyager, Spanning Half-Million Miles A Day, Heading Out Of Range

Paul Recer Associated Press
 

A quarter-century after its launch, Pioneer 10 is still helping astronomers explore the universe. But the little spacecraft is slowly fading from radio contact and will be beyond the reach of even the most sensitive antenna by Christmas next year.

“It will be kind of like losing an old friend,” said John D. Anderson, a Jet Propulsion Laboratory scientist who helped build Pioneer 10.

Since its launch, six presidents have held office, wars have been fought and ended, the Soviet empire has crumbled, and astronauts who walked the moon have become old men. But Pioneer 10 is like that famous battery bunny - it’s still going.

Anderson, who watched Pioneer 10’s launch in March 2, 1972, said the little spacecraft is now more than 6 billion miles from Earth, farther than any other machine ever. It is still streaking away at a speed of more than a half-million miles a day.

NASA scientists stopped sending instructions to Pioneer 10 earlier this year because its return signal was too weak to give clear data. The distance was so great that it took nine hours for a signal to reach the craft. But Anderson said Pioneer 10 can still send back a carrier wave, sort of a radio hum that lets the Earth know it’s OK.

Anderson said NASA, using a 70-meter dish antenna designed for deep space communications, made the last contact Nov. 30.

“It is still quite healthy,” said Anderson. “It’s just that the power source is so weak that you can’t receive the data from scientific instruments.”

All contact will be lost next year, he said, when the craft moves beyond the range of even the most sensitive equipment. The signal will fade and finally become undetectable.

“I’ve made a career of Pioneer 10 and will miss it,” said Anderson. “It will be like losing something that you have a very personal attachment to. It’s kind of like losing an old friend.”

Pioneer 10 was launched as the first probe to Jupiter. After a close-up study of the giant planet, it was accelerated by the slingshot effect of Jupiter’s gravity and gained enough speed to leave the solar system. Since then, it has moved past the orbits of Uranus, Neptune and Pluto, exited the solar system in 1983 and is now in what astronomers called the Kuiper Belt. To Pioneer 10, the sun is only a bright star.

A nuclear heater supplies power to Pioneer 10, and Anderson said the atomic element will continue to work for hundreds of years. In about 30,000 years, he said, the spacecraft will approach another star.

Anderson said the nation got “a bargain” from Pioneer 10’s $100 million cost. It lasted far longer than expected and NASA has built up an extensive library of deep-space data from the craft.

“It will continue to benefit science for decades,” he said. “All of that data has been archived and is available to anyone.”

The Pioneer 10 data, he said, are enabling him and two other scientists to challenge the announced discovery of a planet that is said to orbit a pulsar star 1,200 light-years away.

Anderson said that by comparing the radio energy from the star and Pioneer 10, researchers found evidence that radiation from the sun was causing the radio waves to change slightly every 25 days. He said this change matched the rotation of the sun. This suggested that data interpreted by other researchers as evidence that a small planet orbited the distant pulsar may have been in error.

The electronic blip thought to represent a planet may, in fact, be caused by solar radiation, said Anderson.

Alexander Wolszczan of Pennsylvania State University, co-discover of that distant planet, said he still believes the planet is really there and that new studies will confirm that it is.

But he said he was delighted that Pioneer 10 was “still alive and doing well” and still helping out astronomers.

“It shows there is still some interesting science that can be done with Pioneer 10,” said Wolszczan.


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