From: Jet Propulsion Laboratory
Posted: Friday, December 20, 2002
A thousand years from now NASA's Deep Space 1 probe could make some archeologist very happy.
"We've got it in the tractor beam, doctor!" called the pilot. "It's a small spaceship--an old one by the looks of it."
"About a thousand years old, if I'm right," replied the archeologist. "Will it fit in the cargo hold? Beam it aboard, I want to take a look."
The air shimmered and the craft materialized, suspended in midair. It was a boxy cylinder, about the size of a person, with wings stretching 10 meters from tip-to-tip. "Primitive solar arrays," he nodded. The walls of the craft were blackened from long exposure to space radiation. There was one big dent, as if the craft had strayed too close to an active comet, and lots of tiny pits-a thousand years' worth of micrometeoroid impacts.
A genuine ship from the Early Space Age!
Then he noticed a puffed-out spot in the insulation, and a flap. Something was in there. He reached inside and pulled out a compact disk. Scrawled across it in marker pen were the words: Deep Space 1.
"That's how I imagine it will happen," says Marc Rayman, the project manager of NASA's Deep Space 1 (DS1) mission, who tucked the CD inside his spacecraft just before it was launched in 1998. "The CD is a time capsule," he explains. "It contains information about the spacecraft and its mission, some personal messages from our team and more than 800 drawings made by schoolkids depicting what they think life might be like 1000 years from now."
In the next millennium, he says, elementary students may send probes to other stars as science fair projects. In such an advanced era, "archeologists will be very interested in how we solved our engineering problems back in the late 20th century."
Problem-solving is what Deep Space 1 is all about.
Its mission, sponsored by NASA's New Millennium Program, was to test 12 cutting-edge technologies. Among them: an experimental ion engine, a solar array that focused sunlight for extra power, and an autopilot with artificial intelligence. "There was a good chance DS1 wouldn't work at all; there were so many untried systems on board," recalls Rayman.
It worked so well, however, that NASA approved an extended mission, which Rayman and colleagues had dreamed up even before DS1 left Earth--a visit to a comet. In Sept. 2001, with its technology tests completed and nothing to lose, DS1 swooped past the furiously evaporating nucleus of Comet Borrelly. "We thought the spacecraft might be pulverized," recalls Rayman, but once again DS1 defied the odds. It captured the best-ever view of a comet's heart and emerged intact.
After the comet encounter, the DS1 team conducted a few more technology tests. (That was the "hyper-extended mission," says Rayman.) But time was running out. In December 2001, DS1 had been operating three times longer than originally planned, and it had nearly exhausted its supply of hydrazine--a thruster-gas used to keep the solar arrays pointed toward the Sun. Controllers had no choice but to deactivate the spacecraft.
The mission was over. Or was it?
"I think of it as the beginning ... of the archeology mission," laughs Rayman. "DS1 is still going around the sun in a roughly circular orbit between Earth and Mars--perfect for a time capsule."
Most interplanetary space probes will never be recovered. The Voyager spacecraft, for example, were flung out of the solar system by encounters with Jupiter and Saturn. Ditto for Pioneer 10 and 11. Galileo will crash into Jupiter next year--a deliberate move designed to protect possible life on Jupiter's moon Europa from terrestrial contamination. And Mars orbiters like Viking 1 and 2 will eventually disintegrate in that planet's atmosphere.
Compared to those others, the orbit of Deep Space 1 is stable and accessible.
"Gravitational encounters with Mars and Earth, which happen every few years, and the gentle push of sunlight will act to change the orbit over time--but not much," says Jon Giorgini of the JPL solar system dynamics group. "Using a simple solar radiation pressure model, I integrated the orbit to the year 3002 AD. The orbit's eccentricity, perihelion distance, and inclination will be about the same then as they are now."
"I can't say, however, on which side of the Sun the spacecraft will be in 3002--so the archeologist might have to hunt around a bit." Just enough, perhaps, to add to the thrill of discovery.
And when it's found? "I think it'll go straight to the Smithsonian," predicts Rayman. "The only real question is this: the Smithsonian branch on Earth ... or the one on Mars?"
Editor's Note: There is, of course, no official Deep Space 1 archeology mission. It just happens that DS1 is well-suited for some future archeologist to recover. Why 1000 years from now? It seemed appropriate because DS1 is sponsored by the New Millennium Program.
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