Astronomy and Space


What did NASA mean when it said Voyager 1 and 2 would take a “grand tour” of the planets?

Once every 176 years the giant outer planets—Jupiter, Saturn, Uranus, and Neptune—align themselves in such a pattern that a spacecraft launched from Earth to Jupiter at just the right time might be able to visit the other three planets on the same mission. A technique called “gravity assist” used each planet’s gravity as a power boost to point Voyager toward the next planet. The first opportune year for the “grand tour” was 1977.


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