The Complete Book of Spaceflight: From Apollo 1 to Zero Gravity

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Early Pioneers Pioneer 3 being inspected by technicians
before shipping to Cape Canaveral for launch in 1958. NASA
failed in 1983 after 15 years of service, and Pioneer 7
and 8 were last tracked successfully in the mid-1990s.
Contact with Pioneer 6, the oldest operating spacecraft,
was reestablished on December 8, 2000—35
years after launch.
Pioneer 10 and 11: Jupiter and Beyond
Twin probes that became the first to cross the asteroid
belt and fly past Jupiter. Pioneer 11 used a Jupiter
gravity-assist to redirect it to an encounter with Saturn.
Both spacecraft, along with Voyager 1 and 2, are
now leaving the solar system. Of this interstellar quartet,
only Pioneer 10 is heading in the opposite direc-
Pioneer 10/11 Facts
tion to the Sun’s motion through the galaxy. It continues
to be tracked in an effort to learn more about
the interaction between the heliosphere and the local
interstellar medium. Pioneer 10’s course is taking it
generally toward Aldebaran (65 light-years away) in
the constellation of Taurus, and a remote encounter
about two million years from now. It was superseded
as the most distant human-made object by Voyager 1
in mid-1998. The last communication from Pioneer
11 was received on November 30, 1995. With its
power source exhausted, it can no longer operate any
of its experiments or point its antenna toward Earth,
but it continues its trek in the direction of the constellation
of Aquila. (See table, “Pioneer 10/11 Facts.”)
Pioneer Venus
After a six-month journey, Pioneer Venus 1 entered an
elliptical orbit around Venus in December 1978 and
began a lengthy reconnaissance of the planet. The
spacecraft returned global maps of the Venusian
clouds, atmosphere, and ionosphere, measurements
of the interaction between the atmosphere and the
solar wind, and radar maps of 93% of the planet’s surface.
In 1991, the Radar Mapper was reactivated to
investigate previously inaccessible southern portions
of the planet. In May 1992, Pioneer Venus began the
final phase of its mission, in which the periapsis
(orbital low point) was held at 150 to 250 km until the
fuel ran out and atmospheric entry destroyed the
spacecraft. Despite a planned primary mission duration
of only eight months, the probe remained in
operation until October 8, 1992.
Pioneer Venus 2 consisted of a bus that carried one
large and three small atmospheric probes. The large
Pioneer 10 Pioneer 11
Jupiter flyby
Date Dec. 3, 1973 Dec. 4, 1974
Closest approach
Saturn flyby
130,400 km 43,000 km
Date — Sep. 1, 1979
Closest approach
Status on Jun. 1, 2002
— 21,000 km
Distance 12.2 billion km Mission ended
Speed 12.3 km/s Mission ended