Goals: Pioneer 11 was the first mission to explore Saturn and
the second spacecraft in humanity's early reconnaissance of the
outer solar system. The spacecraft carried instruments to study
magnetic fields, the solar wind and the atmospheres, moons and
other aspects of Jupiter and Saturn. Accomplishments: Among
Pioneer 11's many discoveries are Saturn's F ring and a new
moon. It recorded the planet's overall temperature at -180°C,
indicating that it emits 2.5 times as much heat as it receives
from the Sun. Photographs revealed a more featureless atmosphere
than that of Jupiter, and calculations based on data from
Pioneer 11 suggested that Saturn is primarily liquid hydrogen
with a core of about 10 Earth masses. The dormant spacecraft is
now headed out of our solar system in the general direction of
Sagittarius, toward the center of the galaxy. Both Pioneers 10
and 11 carry a plaque with a message for any intelligent beings
that might find them.