Visit to a Large Planet

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Praise for his lab was well deserved. By any measure, Voyager 1 is a superb technological achievement. It is a stunning example of a machine's ability to be programmed to operate on its own, without human "joy-sticking," as the NASA people put it, from folks on the ground. Voyager 1 is even capable of making its own repairs and correcting navigational errors by itself.

With the reconnaissance of Saturn, the U.S. has completed a close-up inspection of all the planets visible to the ancients, before the advent of the telescope. During this past decade, robot spacecraft provided the first look at the parched, cratered surface of Mercury, the sun's nearest planet. With cameras and radar they inspected cloud-shrouded Venus, a hot, almost hellish sphere with a surface temperature of about 480° C (900° F) and a crushingly thick atmosphere of carbon dioxide. From both overhead and on the ground they surveyed Mars, finally laying to rest the myth that canals exist on the Red Planet. Two Viking landers even sampled the Martian soil in hopes of detecting biological activity. (Edgar Rice Burroughs notwithstanding, they found not a trace of life.) Reaching farther into space, unmanned envoys from earth approached mighty Jupiter, largest of the planets. Back came stunning color portraits of that multihued sphere and close-ups of the Jovian moons, including tiny lo, which was caught in the act of surprising volcanic eruptions. Says Astronomer Carl Sagan: "I can't imagine anyone remaining blase in the face of such accomplishments."

Voyager 1's three years of space exploration were the result of more than ten years of preparation. The original idea grew out of a rare astronomical event that would occur in the late 1970s. Once every 175 years during their slow travels around the sun, the large outer planets —Jupiter, Saturn, Uranus and Neptune —line up almost like a column of toy soldiers. Using their gravitational pull, scientists calculated, a spacecraft could, literally, hop from one planet to another, eventually flying past all of them. In late 1970 NASA officials, still basking in the glow of the moon landings, decided to take advantage of the unusual planetary configuration by staging what became known as the Grand Tour, a visit to all these planets, if possible by the end of the 1980s.

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