Letter From Discover

Monday, August 02, 2004

THE LONG AND WINDING ROAD TO THE RINGED PLANET

Courtesy of the Smithsonian Institution Libraries/Dibner Library of Science and Technology, Washington,D.C.

A 17th-century drawing of Saturn, made by Dutch astronomer Christiaan Huygens, depicts early efforts to understand the planet’s enigmatic rings. More than three centuries later the rings are still a source of mystery and scientific amazement.

As glorious photos of Saturn start enlivening the morning papers and the evening news, you aren’t likely to hear much about the physical achievements of the Cassini explorer that’s snapping the pictures. Although phrases like “most complex probe ever built” or “one of NASA’s most ambitious missions” will be thrown around, the numbers are so astonishing that they defy easy description.

Try to comprehend, for starters, the distance from Earth to Saturn—929 million miles as of August 1. That’s about 4,000 times farther than the Apollo astronauts traveled to the moon and almost 10 times the distance from Earth to the sun. Cassini’s journey was even longer than that because the United States’ largest booster, the Titan IV-B Centaur, didn’t have enough power to take a direct course. The spacecraft had to travel 2.2 billion miles in getting to Saturn, using four roundabout gravity boosts involving flybys of Venus, Earth, and Jupiter.

The Cassini package is physically huge—more than 20 feet long and 12,600 pounds fully fueled—and financially large as well. Ultimately, the mission will cost more than $3 billion, a hefty price tag in an era of cutbacks in federal spending on space exploration.

Don’t expect to see the likes of Cassini again anytime soon. Grand explorations of our solar system are unfortunately rare these days, even though such missions keep us in a state of awe and wonder like nothing else. Until a few months ago, the only good photos of Saturn were taken two decades ago by the two Voyager spacecraft. Yet every time Discover published one of them, readers responded with fresh excitement. Saturn is big. It deserves a big, complex, long-lived spacecraft.

You’ll be hearing more about Cassini in coming issues of Discover. We look forward—ever optimistic—to a future in which we don’t have to wait another 20 years to share the next triumph with you.

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