Pioneer 11 is an unmanned space probe that visited Jupiter, Saturn, and its moons. It was launched in 1973 and passed by Jupiter in 1974, taking images of the Great Red Spot and measuring the mass of Callisto. It then passed by Saturn in 1979, making density measurements of the ring’s particles and determining they were not dangerous to incoming probes. Pioneer 11 will pass by a star in about four million years.
Pioneer 11 is an unmanned space probe, the second to have crossed the asteroid belt and visited Jupiter and its moons. Unlike its predecessor and twin, Pioneer 2, it has also visited Saturn, using gravitational assistance from Jupiter. The probe then exited the solar system, heading in the direction of the constellation Aquila. It will pass by one of the stars in about four million years.
Pioneer 11 was launched from Cape Canaveral, Florida, USA on April 6, 1973, one month after its twin. Although originally intended only to visit Jupiter, Pioneer 11 was redirected mid-mission to visit Saturn. Ironically, the accompanying Pioneer 11 plaque, intended for possible extraterrestrials, indicates that it left the solar system through some help from Jupiter, although this is false.
On December 4, 1974, a year and a half after launch, Pioneer 11 passed within 34,000 km of Jupiter’s cloud tops, taking fantastic images of the Great Red Spot and measuring the mass of the moon Callisto. Using a gravity assist, it continued toward Saturn.
Pioneer 11 passed by Saturn on Sept. 1, reaching a distance of 1979 km from the cloud tops. The first spacecraft ever to orbit Saturn, it made density measurements of the ring’s particles, making sure the planetary zone was safe for the incoming Voyager spacecraft, which had already passed Jupiter and was en route. Had it been determined that the ring particles would be dangerous to the probes, they would have been diverted away from the planet’s immediate vicinity to avoid the rings, but would have missed the gravity assist opportunity to visit the other outer planets, Uranus and Neptune. He determined the dust was too fine to harm space probes there.
During its visit to the Saturn system, Pioneer 11 photographed and nearly collided with the small moon Epimetheus, whose existence had been suspected but not confirmed by astronomers. Among other measurements made were that Saturn’s moon Titan was probably too cold to live.
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