On September 1st, 1979, Pioneer 11 became the first
spacecraft to successfully visit Saturn. It was thirty years ago today when mankind
was able to get up close and personal with our solar system's ringed planet via
a remarkable unmanned spacecraft.
O Pioneers!
While the literary allusion
in the headline above was unavoidable, I'll curb the topic of 20th
century American literature for now by keeping things focused on the cosmos. It
is notable, however, that the Pioneer 11 shared a number of qualities with a
close relative. Pioneer 10 was launched toward Jupiter in 1972 in order to
investigate Jupiter, Saturn, and the Milky Way, but subsequently passed through
an asteroid belt before recording close-up images of Jupiter. Later, Pioneer 11
was launched from Cape Canaveral on a similar
trajectory on April 6th, 1973 on top of an Atlas/Centaur/TE364-4 launch vehicle
in order to perhaps reach farther limits.
Although Pioneer 11 did not make contact with the ringed
planet until this day 30 years ago, credit should be given to NASA's Lewis
Team, which was led by Bruce T. Lundin. As
Lundin's "Go Atlas! Go Centaur!" cry during the final countdown of Atlas/Centaur/TE364-4's
launch might have boosted the team's spirit, it was mostly the vehicle's
solid-fueled TE364-4 third stage of power that helped create approximately
15,000 pounds of thrust. This, in addition to Atlas's liquid oxygen propellant
and the Centaur's liquid hydrogen and liquid oxygen cocktail, assured the team
that Pioneer 11 would be able to lift off much like its predecessor.
Cosmic Greeting
While the Pioneer 11 was headed on much the same mission as
Pioneer 10 (to primarily investigate Jupiter), it exceeded its expectations by
becoming the first spacecraft to visit Saturn and its main rings. According to
NASA specs, Pioneer 11 contained two nuclear electric-power generators able to
produce 144 watts at Jupiter, but later decreased to 100 watts when it reached
Saturn. The spacecraft actually used Jupiter's gravitational field to alter its
trajectory, and as it neared Saturn, it gained photo opportunities of a planet
that is over 70,000 miles from us.
 As Pioneer 11 passed Saturn on September 1st, it, just like
Pioneer 10, contained a plaque
that had a famous drawing depicting a man, a woman, and the location of the sun
and earth in the galaxy. Think of it as an official extraterrestrial greeting
card!
The Silencing of a
Pioneer
After its visitation with Saturn, Pioneer 11 ventured into
the outer regions of the Solar System in order to study solar wind and cosmic
rays entering portions of the Milky Way. Unfortunately, by September 1995,
Pioneer 11 was at a distance of roughly 4 billion miles away from Earth when its
power source was decreasing rapidly. Since Pioneer 11 became incapable of
making scientific observations at that point, routine mission operations were
terminated and the spacecraft essentially retired on the day of its last
communication with Earth: November 11th, 1995.
Resources:
NASA's Glenn Research Center
and Data Specs: http://www.nasa.gov/centers/glenn/about/history/pioneer.html,
http://nssdc.gsfc.nasa.gov/nmc/masterCatalog.do?sc=1973-019A
Saturn Fact Sheet: http://nssdc.gsfc.nasa.gov/planetary/factsheet/saturnfact.html
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