Slice of History - Marking 45 Years Since Passing the Rings of Saturn

A sister spacecraft to Pioneer 10, Pioneer 11 was the first spacecraft to study Saturn up close and returned the first images of the polar regions of Jupiter. During its outbound journey, Pioneer 11 experienced several malfunctions, including the momentary failure of one of the RTG booms to deploy, a problem with an attitude control thruster, and the partial failure of the asteroidal dust detector, yet none of these issues jeopardized its mission.

Pioneer detected Saturn’s bow shock about 932,000 miles (1.5 million kilometers) out from the planet, thus providing the first conclusive evidence of the existence of Saturn’s magnetic field. The spacecraft crossed the planet’s ring plane beyond the outer ring on 1 September, then passed by the planet for a close encounter at a range of about 13,000 miles, taking 440 images of the planetary system along the way, including the one above. Saturn's moon Rhea, seen as a speck of light near the planet on the right, is the sixth moon out from Saturn. It is 1000 miles (1600 kilometers) in diameter, about half the size of Earth's moon.

Heading out further into the solar system, Pioneer crossed Neptune’s orbit in 1990, and by 1995, 22 years after launch, two instruments were still operational. But by the end of that year, NASA Ames Research Center made last contact with the spacecraft, and according to Project Manager, Fred Wirth, “Pioneer 11 will travel as a ghost ship in our galaxy.” CL#23-6606

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