Exploration of Saturn
|
System
Spacecraft |
Jupiter | Saturn | Uranus | Neptune | Pluto |
|---|---|---|---|---|---|
| Pioneer 10 | 1973 flyby | ||||
| Pioneer 11 | 1974 flyby | 1979 flyby | |||
| Voyager 1 | 1979 flyby | 1980 flyby | |||
| Voyager 2 | 1979 flyby | 1981 flyby | 1986 flyby | 1989 flyby | |
| Galileo |
1995–2003 orbiter; 1995, 2003 atmospheric |
||||
| Ulysses | 1992, 2004 gravity assist | ||||
| Cassini–Huygens | 2000 gravity assist |
2004– orbiter; 2005 Titan lander |
|||
| New Horizons | 2007 gravity assist | 2015 flyby | |||
| Juno | 2016– orbiter |
The exploration of Saturn has been solely performed by unmanned probes. Three missions were flybys, which formed an extended foundation of knowledge about the system. The Cassini–Huygens spacecraft was launched in 1997; the Cassini spacecraft has been in orbit since 2004.
Saturn was first visited by Pioneer 11 in September 1979. It flew within 20,000 km of the top of the planet's cloud layer. Low-resolution images were acquired of the planet and a few of its moons; the resolution of the images was not good enough to discern surface features. The spacecraft also studied the rings; among the discoveries were the thin F-ring and the fact that dark gaps in the rings are bright when viewed towards the Sun, or in other words, they are not empty of material. Pioneer 11 also measured the temperature of Titan at 250 K.
In November 1980, the Voyager 1 probe visited the Saturn system. It sent back the first high-resolution images of the planet, rings, and satellites. Surface features of various moons were seen for the first time. Because of the earlier discovery of a thick atmosphere on Titan, the Voyager controllers at the Jet Propulsion Laboratory elected for Voyager 1 to make a close approach of Titan. This greatly increased knowledge of the atmosphere of the moon, but also proved that Titan's atmosphere is impenetrable in visible wavelengths, so no surface details were seen. The flyby also changed the spacecraft's trajectory out from the plane of the Solar System which prevented Voyager 1 from completing the Planetary Grand Tour of Uranus, Neptune and Pluto.
Almost a year later, in August 1981, Voyager 2 continued the study of the Saturn system. More close-up images of Saturn's moons were acquired, as well as evidence of changes in the rings. Voyager 2 probed Saturn's upper atmosphere with its radar, to measure temperature and density profiles. Voyager 2 found that at the highest levels (7 kilopascals pressure) Saturn's temperature was 70 K (−203 °C) (i.e. 70 degrees above absolute zero), while at the deepest levels measured (120 kilopascals) the temperature increased to 143 K (−130 °C). The north pole was found to be 10 K cooler, although this may be seasonal. Unfortunately, during the flyby, the probe's turnable camera platform stuck for a couple of days and some planned imaging was lost. Saturn's gravity was used to direct the spacecraft's trajectory towards Uranus.
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Wikipedia