Roanoke Times
Copyright (c) 1995, Landmark Communications, Inc.
DATE: MONDAY, March 2, 1992 TAG: 9203020269
SECTION: NATIONAL/INTERNATIONAL PAGE: A-10 EDITION: METRO
SOURCE: Associated Press
DATELINE: CAPE CANAVERAL, FLA. LENGTH: Medium
The nuclear-powered spacecraft is now 5 billion miles away - farther from Earth than any other human-made object - and still beaming back precious scientific data as it hurtles deeper and deeper into space.
"The great technical miracle of the whole thing is that we can receive intelligible data from 5 billion miles away using only 8 watts of radio power. That's a great human achievement," said University of Iowa physicist James Van Allen, principal investigator of one of Pioneer 10's telescopes.
The faint radio pulses eventually will disappear and power to the scientific instruments will cease, probably around the year 2000. But Pioneer 10's odyssey will go on and on, barring collision or capture by space beings.
No one knew what to expect when Pioneer 10 was hoisted into space by an Atlas-Centaur rocket on March 2, 1972. The 570-pound craft was designed to operate for a minimum 21 months, just long enough to fly by Jupiter and take pictures of the mysterious, giant planet.
NASA worried whether the aluminum and magnesium probe would make it through the asteroid belt, a massive band of rock and dust orbiting between Mars and Jupiter. A spacecraft had never passed this way before.
Pioneer 10 entered the asteroid belt in July 1972 and emerged unscathed seven months later. The spacecraft survived another trial in December 1973 in Jupiter's intense radiation belts.
The probe swept safely within 81,000 miles of Jupiter and provided the first close-up views of the cloud-covered planet. The planet's gravity propelled the craft toward the outer reaches of the solar system.
When Pioneer 10 crossed Neptune's orbit in 1983 it became the first human-made object to leave the solar system.
If it continues on its path, barreling along at 28,900 mph, it would pass within three light years of a star called Ross 248 in 32,610 years.
Seven of the probe's 11 scientific instruments still work, including Van Allen's telescope. They monitor solar wind, cosmic particles and ultraviolet glow. Scientists scrutinize the data for evidence of a 10th planet and signs of the heliopause, the outer limits of the sun's influence.
Pioneer 10's radio signals take 7 1/2 hours to reach Earth. The 8 watts of power in each signal is the equivalent of a night light. By the time the signal reaches Earth and the huge antennas of NASA's Deep Space Network, the power measures 4.2 billionth of a trillionth of a watt.
For anyone or anything that might be out there, Pioneer 10 bears a plaque. It shows a naked man and woman - which caused a fuss at the time of launch - standing side by side. The man's right hand is raised in greeting.
The nine planets also are depicted, as well as the spacecraft's path. A burst of radiating lines indicate the distance and direction from the sun to 14 pulsars, or pulsating stars, and the frequency of those pulsars at the time of launch.
by CNB