Pioneer 10 gets new lease on life in outer solar system
Artist's concept of Pioneer as it passed Saturn
MOFFETT FIELD, California (CNN) -- Pioneer 10 weathered boulders
in the asteroid belt, intense radiation near Jupiter and a flyby with a mysterious object beyond Pluto. But the mission seemed
doomed to perish from an Earthly threat, until chaos theory intervened.
| IMAGE GALLERY
| MESSAGE BOARD
Launched on March 2 in 1972, Pioneer still performs valuable
scientific observations, but almost died for lack of funding
a few years ago. That was until scientists studying chaos
theory became interested in its weak signals, which take
about 10 hours to reach Earth, traveling at the speed of
The faint radio transmissions are being read for advanced
concept support of chaos theory, according to Pioneer 10
mission leader Larry Lasher, who called the new project a
An impressive list of firsts
Pioneer has racked up impressive achievements during a
28-year voyage that has taken it almost 7 billion miles, about
twice the distance of Pluto from the sun. It was the first
spacecraft to pass beyond Pluto's orbit and the first to make direct
observations and take close-up pictures of Jupiter.
Pioneer 10 charted Jupiter's intense radiation belts and
verified that the jovian planet is mostly liquid.
But many astronomers consider Pioneer 10's unprecedented
passage through the asteroid belt between Mars and Jupiter as
its crowning accomplishment.
No one knew if a spacecraft could navigate the cosmic mine field, filled with speeding boulders, some the size of Alaska. Pioneer 10 made the crossing virtually untouched, opening the way for later spacecraft to voyage beyond Mars.
The edge of the solar system
Pioneer 10 is now about 75 astronomical units away from
the sun, or 75 times the distance of the Earth from the sun.
Scientists still can receive data from a low-watt
telescope, but the craft, its nuclear-powered battery supply
dwindling, dare not turn on its instruments for fear of a
power outage, said Lasher, who works for NASA's Ames research center in Moffett Field, California.
The craft recently performed a maneuver to improve the
reception of its signal on Earth, but had to turn off its
transmitter and fly blindly for 90 minutes to do so.
When Pioneer was 5.2 billion miles away, it was knocked off course by a mysterious gravitation tug. Astronomers think the cause was a Kuiper Belt Object. KBOs are asteroid-sized bodies, similar in make up as Pluto, that circle the sun far beyond Pluto.
Pioneer faces another great challenge: searching for the edge
of the solar system. It could close in soon on the outer
reaches of the heliosphere, an elliptical field of solar wind
that radiates from the sun. At the edge, where the solar
system meets outer space, the interstellar ray flux stops the
solar winds in their tracks.
"We're hoping we are at the point where we can make that
determination soon," said Lasher, who estimates the boundary
at a distance of 75 to 125 AUs.
"We think that it's pretty close, but our hopes are dashed
all the time," he said.
Passing the baton to Voyager 1
Scientists once thought the heliosphere extended out only as
far as Jupiter, a theory dashed by Pioneer and other veteran
travelers into the outer solar system -- Voyager 1 and 2.
Launched in 1977, the Voyagers have similar records of
achievement as Pioneer 10. Both Voyagers flew by Saturn and
Jupiter. Voyager 2 also passed near Uranus and Neptune.
But they have taken far different paths. The Voyagers are
heading in the opposite direction than Pioneer, in relation
to the sun.
The Voyagers, both well beyond Pluto, could have better luck
in their search for the edge of the heliosphere. In 1998, Pioneer "passed the baton," Lasher said, to the faster Voyager I as the most
distant manmade object in the solar system.
Pioneer should stop sending transmissions in the coming years.
But having used planetary gravitational assists to reach escape velocity from the solar system, it will continue to drift into interstellar space for millions of years. It is headed at 27,380 mph for the red
star Aldebaran, which makes the eye of Taurus, the Bull.
Pioneer will need more 2 million years to reach it.
It will probably still be chugging through the galaxy 5
billion years from now when the sun expands into a red giant
and obliterates Earth.
Should other sentient life forms find Pioneer, however, they
may learn about humans. The ship carries a plaque, designed
in part by the late Dr. Carl Sagan, engraved with pictures,
solar maps and elemental symbols to describe civilization on
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