Seven Billion Miles and
Last week NASA received a weak signal from Pioneer 10,
twice as far from the Sun as Pluto and speeding toward
the constellation Taurus.
Listen to this story (requires RealPlayer)
May 3, 2001 -- On April 28th, a Deep
Space Network antenna in Madrid detected
a curious radio transmission from the
constellation Taurus. The feeble signal
registered little more than a billionth of a
trillionth of a watt -- nonetheless, it had a
powerful effect on scientists.
The signal was intelligent and it came from
an interstellar spacecraft about twice as far
from the Sun as Pluto. It was Pioneer 10!
Right: An artist's rendering of the Pioneer
spacecraft in deep space.
Ground controllers had been listening for the distant space probe since last August with no
success, raising fears that its radio transmitter had finally run out of power after 29 years in
space. But, says delighted Pioneer 10 project manager Larry Lasher at NASA/Ames,
"Pioneer 10 lives on!"
Pioneer 10 was launched on March 2, 1972, from Cape Kennedy aboard an Atlas Centaur
rocket. At the time it was the fastest spacecraft ever to leave Earth. It was the first
spacecraft to travel through the asteroid belt, the first to visit Jupiter, and the first to use a
planet's gravity to change course and reach solar-system escape velocity. Now, as it races
for interstellar space, Pioneer 10 faces its toughest challenge yet: the inexorable march of
"We're way beyond our warranty," says Lasher. "Pioneer 10 was only
intended to last 21 months, but it's been going for nearly 30 years." The
craft is powered by electricity derived from the warmth of decaying
plutonium 238. Although the half-life of the isotope is 92 years, the
thermocouples that convert heat energy to electricity are degrading
faster. Mission controllers suspect there won't be enough electricity to
power the radio transmitter much longer.
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Seven Billion Miles and Counting....