JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109. TELEPHONE (818) 354-5011
Mary A. Hardin (818) 354-0344
IMMEDIATE RELEASEFebruary 13, 1998
1 NOW MOST DISTANT HUMAN-MADE OBJECT IN SPACE
In a dark, cold, vacant neighborhood near the very edge of
our solar system, the Voyager 1 spacecraft is set to break
another record and become the explorer that has traveled farthest
At approximately 2:10 p.m. Pacific time on February 17, 1998,
Voyager 1, launched more than two decades ago, will cruise
beyond the Pioneer 10 spacecraft and become the most distant
human-created object in space at 10.4 billion kilometers (6.5
billion miles.) The two are headed in almost opposite directions
away from the Sun. As with other spacecraft traveling past
the orbit of Mars, both Voyager and Pioneer derive their electrical
power from onboard nuclear batteries.
25 years, the Pioneer 10 spacecraft led the way, pressing
the frontiers of exploration, and now the baton is being passed
from Pioneer 10 to Voyager 1 to continue exploring where no
one has gone before," said Dr. Edward C. Stone, Voyager
project scientist and director of NASA's Jet Propulsion Laboratory.
almost 70 times farther from the Sun than the Earth, Voyager
1 is at the very edge of the Solar System. The Sun there is
only 1/5,000th as bright as here on Earth -- so it is extremely
cold and there is very little solar energy to keep the spacecraft
warm or to provide electrical power. The reason we can continue
to operate at such great distances from the Sun is because
we have radioisotope thermal electric generators (RTGs) on
the spacecraft that create electricity and keep the spacecraft
operating," Stone said. "The fact that the spacecraft
is still returning data is a remarkable technical achievement."
Voyager 1 was launched from Cape Canaveral on September 5,
1977. The spacecraft encountered Jupiter on March 5, 1979,
and Saturn on November 12, 1980.
Then, because its trajectory was designed to fly close to
Saturn's large moon Titan, Voyager 1's path was bent northward
by Saturn's gravity, sending the spacecraft out of the ecliptic
plane - the plane in which all the planets except Pluto orbit
Launched on March 2, 1972, the Pioneer 10 mission officially
ended on March 31, 1997. However NASA's Ames Research Center,
Moffet Field, CA, intermittently receives science data from
Pioneer as part of a training program for flight controllers
of the Lunar Prospector spacecraft now orbiting the Moon.
Voyager mission today presents an unequaled technical challenge.
The spacecraft are now so far from home that it takes nine
hours and 36 minutes for a radio signal traveling at the speed
of light to reach Earth,"said Ed B. Massey, project manager
for the Voyager Interstellar Mission. "That signal, produced
by a 20 watt radio transmitter, is so faint that the amount
of power reaching our antennas is 20 billion times smaller
than the power of a digital watch battery,"
Having completed their planetary explorations, Voyager 1 and
its twin, Voyager 2, are studying the environment of space
in the outer solar system. Although beyond the orbits of all
the planets, the spacecraft still are well within the boundary
of the Sun's magnetic field, called the heliosphere. Science
instruments on both spacecraft sense signals that scientists
believe are coming from the outermost edge of the heliosphere,
known as the heliopause.
The heliosphere results from the Sun emitting a steady flow
of electrically charged particles called the solar wind. As
the solar wind expands supersonically into space in all directions,
it creates a magnetized bubble -- the heliosphere -- around
the Sun. Eventually, the solar wind encounters the electrically
charged particles and magnetic field in the interstellar gas.
In this zone the solar wind abruptly slows down from supersonic
to subsonic speed, creating a termination shock. Before the
spacecraft travel beyond the heliopause into interstellar
space, they will pass through this termination shock.
data coming back from Voyager now suggest that we may pass
through the termination shock in the next three to five years,"
Stone said. "If that's the case, then one would expect
that within 10 years or so we would actually be very close
to penetrating the heliopause itself and entering into interstellar
space for the first time."
Reaching the termination shock and heliopause will be major
milestones for the mission because no spacecraft have been
there before and the Voyagers will gather the first direct
evidence of their structure. Encountering the termination
shock and heliopause has been a long-sought goal for many
space physicists, and exactly where these two boundaries are
located and what they are like still remains a mystery.
Science data are returned to Earth in real-time to the 34-
meter Deep Space Network (DSN) antennas located in California,
Australia and Spain. Both spacecraft have enough electricity
and attitude control propellant to continue operating until
about 2020, when electrical power produced by the RTGs will
no longer support science instrument operation. At that time,
Voyager 1 will be almost 150 times farther from the Sun than
the Earth -- more than 20 billion kilometers (almost 14 billion
On Feb. 17, Voyager 1 will be 10.4 billion kilometers (6.5
billion miles) from Earth and is departing the Solar System
at a speed of 17.4 kilometers per second (39,000 miles per
hour). At the same time, Voyager 2 will be 8.1 billion kilometers
(5.1 billion miles) from Earth and is departing the solar
system at a speed of 15.9 kilometers per second (35,000 miles
JPL, a division of the California Institute of Technology,
manages the Voyager Interstellar Mission for NASA's Office
of Space Science, Washington, D. C.