| By
ANDREW BRIDGES AP Science Writer
NASA
scientists said Sunday they have contacted the Pioneer 10
spacecraft, ending fears that the robotic probe had gone
silent 29 years into a mission that has carried it more
than 7 billion miles from Earth.
A radio
antenna outside Madrid received a signal from Pioneer 10
on Saturday, marking the first time the spacecraft had been
heard from since Aug. 19. The spacecraft was launched March
2, 1972.
``Pioneer
10 lives on,'' project manager Larry Lasher said in a status
report posted Sunday on the mission's Web site.
Pioneer
10 was the first spacecraft to pass through the asteroid
belt and the first to obtain close-up images of Jupiter.
In 1983, it became the first manmade object to leave the
solar system when it passed the orbit of distant Pluto.
The
spacecraft is currently 7.29 billion miles from Earth, traveling
at 27,380 mph relative to the sun. At that distance, radio
signals take 21 hours and 45 minutes to make the roundtrip
between the Earth and the spacecraft.
The
Pioneer 10 mission came to a formal close in 1997, but the
probe had remained in fairly regular contact with Earth,
returning limited scientific data before going silent in
August.
Picking
out the faint signal of the spacecraft's eight-watt transmitter
put the National Aeronautics and Space Administration's
international network of antennas to the test. Further communications
with Pioneer likely will remain difficult, because engineers
can contact the spacecraft only by first beaming signals
to it.
``In
order (for Pioneer 10) to talk to us, we need to talk to
it,'' said Ric Campo, the mission's chief flight controller.
Even
in silence, the spacecraft will continue its steady voyage
toward the constellation Taurus. It should pass one of the
stars in the constellation more than 2 million years from
now.
The
spacecraft carries a gold plaque engraved with a message
of goodwill and a map showing the Earth's location within
the solar system.
NASA's
oldest operating spacecraft is Pioneer 6, which scientists
contacted in December to mark the 35th anniversary of its
launch.
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