Pioneer Saturn EncounterUnited States. National Aeronautics and Space Administration
Science
Pioneer Saturn Encounter
United States. National Aeronautics and Space Administration
Pioneer (Space probes); Saturn probes
[Illustration: Close-up image from Pioneer Saturn of Saturn from a
distance of 400,000 km (September 1, 1979, a few hours before
closest approach). Inset shows the location of the image on the
planet. The part of the disk shown is about 25,000 by 70,000 km. The
sawtooth pattern is an artifact. The vertical stripe on the disk is
due to a gain change in the instrument. The image has not had its
final corrections for shape. The rings and their shadows cut
diagonal swaths across the image with the upper swath being the
shadow. The rings, seen from the unlit side, are visible in the
foreground. The ring shadow shows clearly that Saturn’s rings have
two major divisions: the Cassini Division dividing the outer A-ring
from the middle B-ring, and a second division (previously
controversial) dividing the B-ring from the inner C-ring. These
divisions show as parallel pinstripes in the broad black band of the
rings’ shadow, with the upper stripe being the Cassini Division.
Some shearing in the bands and belts on Saturn’s disk is beginning
to appear, although the low contrast on the planet (due to its
high-altitude haze) does not make this highly evident.]
[Illustration: Post-encounter image of Saturn from a distance of
850,000 km (September 2, 1979, 15 hours after encounter). As
planned, during the encounter Saturn’s gravitational field turned
the spacecraft’s trajectory behind the planet and out toward the
edge of the solar system at approximately a right angle to the
inbound trajectory. Thus, the planet is now illuminated from the
side, and the view is of a crescent Saturn with the terminator on
the right of the picture. The rings appear dim when compared with
the previous inbound pictures because of the different angle between
the sun, the rings, and the spacecraft. When this picture was taken,
the spacecraft, as seen from Earth, was about to pass behind the
sun, and solar activity was interfering with spacecraft
communications. The image quality, therefore, is not as good as for
pictures taken inbound. With this farewell image from Pioneer,
Saturn waits for the Voyager spacecraft in 1980 and 1981.]
[Illustration: This image of cloud-covered Titan is one of the
“firsts” for the Pioneer Saturn mission. Titan is the largest of
Saturn’s moons. Because of its great distance from Earth, however,
Titan can be seen only as a point of light in Earth-based pictures.
The Pioneer trajectory could not be adjusted to allow passage close
to Titan, and imaging of the planet from the spacecraft was at the
outer range of capability of the imaging instrument. Thus, the fuzzy
edges and contrast variations on the moon should not be construed as
surface features.
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