Steven Dutch, Professor Emeritus, Natural and Applied Sciences, Universityof Wisconsin - Green Bay
The first spacecraft to visit Saturn was actually Pioneer 11,
Pioneer 11 discovered a narrow ring, the F ring, just outside the A ring, and imagedone new satellite. It discovered a second satellite the hard way by almost colliding withit. It did not take a picture of the satellite but passed close enough behind it to senseits disturbance of Saturn's magnetic field.
Some of the hot-dogger types at NASA wanted to fly Pioneer 11 through the CassiniDivision, but cooler heads prevailed, pointing out that there might be a lot of orbitingdebris in the gap. This turned out to be true; images of the shaded side of Saturn's ringsshowed the gap brilliantly lit by sunlight reflected off fine particles. Flying throughthe Cassini Division would have been the equivalent of emptying buckshot into thespacecraft - a spectacular end to the mission, to be sure, but not a good use of aspacecraft.
Voyager 1 passed closer to Jupiter and got a greater gravitational boost than Voyager2, so it arrived at Saturn nine months earlier. In addition to imaging Saturn and theshaded side of its rings, it got good images of the satellites Mimas, Dione and Rhea. Italso passed close by Titan; unfortunately, this maneuver put Voyager 1 on a path steeplyinclined to the plane of the Solar System so that it could not make any further planetaryencounters.
Voyager 2 viewed the sunlit side of Saturn's rings and got closeups of the satellitesIapetus, Hyperion, Enceladus and Tethys, and very crude distant images of the distantoutermost moon Phoebe. A lubrication problem in the scan platform caused some of the bestpictures to be lost but the problem was resolved in time to permit successful flybys ofUranus and Neptune.
Between Voyager's visit to Saturn and its arrival at Uranus in 1986, Voyager 2 wasessentially re-engineered. Its computer was almost completely reprogrammed from Earth.Particular problems to be solved included compensating for the mechanical limitations ofthe partially-disabled camera boom, devising better data transmission and storage routinesto compensate for the longer signal time to and from Earth, and providing for longerexposure times to compensate for the low light levels in the outer Solar System. To takesome of its photos, Voyager would have to roll at a carefully-controlled rate tocompensate for its own motion during the long exposure.
Voyager successfully imaged Uranus and its rings and the five large moons of Uranus. Italso discovered numerous new small moons, including shepherd moons for some of the rings.
Voyager succesfully imaged Neptune and its rings. The rings, previously thought to beincomplete ring arcs, were shown to be complete but uneven. Voyager obtained good closeupsof part of Neptune's large moon Triton. The other previously known moon Nereid was onlyimaged from a great distance. In addition, Voyager discovered a number of new moons, oneof which is larger than Nereid.
Four spacecraft have now left the Solar System: Pioneer 10 and 11, and Voyager1 and 2. On February 14, 1990, Voyager 1 turned on its cameras one last time andtook a photograph of the entire solar system. Actually, only six planets were imaged;Mercury and Mars were too close to the Sun from Voyager's vantage point to see andwere lost in the solar glare, and Pluto is too faint. The picture is not widely publishedbecause there's not much to see: 60 mostly blank frames with the planets as tiny dots in afew of them.
On February 17, 1998, Voyager 1's greater speed finally overcame Pioneer 10'slong head start and Voyager 1 became the most distant human object. Both spacecraftwere 10.4 billion kilometers from the Sun. Voyager 1 is receding from the Solar System at17.4 km/second (almost 40,000 miles an hour). Voyager 1 is moving in roughly thesame direction as the Solar System, and its last major mission is to explore the heliopause;the shock wave that occurs when particles flowing outward from the Sun impact the gases ofinterstellar space. Voyager 1 is expected to encounter the heliopause sometime inthe next few years.
Carrying on a tradition begun by the Pioneers, the Voyagers carried a record of humanculture on a phonograph record.
Note: you will need to visit the planetary sites for some of this information.
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Created 18 March 1998, Last Update 15 January 2020