64 Voyager (outer planet flybys) (US planetary missions)
Description
This article is from the Space FAQ, by Jon Leech leech@cs.unc.edu and Mark Bradford tla@surly.org with numerous contributions by others.
64 Voyager (outer planet flybys) (US planetary missions)
VOYAGER 1 was launched September 5, 1977, and flew past Jupiter on March
5, 1979 and by Saturn on November 13, 1980. VOYAGER 2 was launched
August 20, 1977 (before VOYAGER 1), and flew by Jupiter on August 7,
1979, by Saturn on August 26, 1981, by Uranus on January 24, 1986, and
by Neptune on August 8, 1989. VOYAGER 2 took advantage of a rare
once-every-189-years alignment to slingshot its way from outer planet to
outer planet. VOYAGER 1 could, in principle, have headed towards Pluto,
but JPL opted for the sure thing of a Titan close up.
Between the two probes, our knowledge of the 4 giant planets, their
satellites, and their rings has become immense. VOYAGER 1&2 discovered
that Jupiter has complicated atmospheric dynamics, lightning and
aurorae. Three new satellites were discovered. Two of the major
surprises were that Jupiter has rings and that Io has active sulfurous
volcanoes, with major effects on the Jovian magnetosphere.
When the two probes reached Saturn, they discovered over 1000 ringlets
and 7 satellites, including the predicted shepherd satellites that keep
the rings stable. The weather was tame compared with Jupiter: massive
jet streams with minimal variance (a 33-year great white spot/band cycle
is known). Titan's atmosphere was smoggy. Mimas' appearance was
startling: one massive impact crater gave it the Death Star appearance.
The big surprise here was the stranger aspects of the rings. Braids,
kinks, and spokes were both unexpected and difficult to explain.
VOYAGER 2, thanks to heroic engineering and programming efforts,
continued the mission to Uranus and Neptune. Uranus itself was highly
monochromatic in appearance. One oddity was that its magnetic axis was
found to be highly skewed from the already completely skewed rotational
axis, giving Uranus a peculiar magnetosphere. Icy channels were found on
Ariel, and Miranda was a bizarre patchwork of different terrains. 10
satellites and one more ring were discovered.
In contrast to Uranus, Neptune was found to have rather active weather,
including numerous cloud features. The ring arcs turned out to be bright
patches on one ring. Two other rings, and 6 other satellites, were
discovered. Neptune's magnetic axis was also skewed. Triton had a
canteloupe appearance and geysers. (What's liquid at 38K?)
The two VOYAGERs are expected to last for about two more decades. Their
on-target journeying gives negative evidence about possible planets
beyond Pluto. Their next major scientific discovery should be the
location of the heliopause. Low-frequency radio emissions believed to
originate at the heliopause have been detected by both VOYAGERs.
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