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David McAlary
 
For weeks, two helicopter crews have been practicing the mid-air capture of a parachute drifting down over the Utah desert.

When the event acttually occurs Wednesday, the parachute will be carrying grains of solar particles gathered by the U.S. Genesis spacecraft, which has been orbiting around an empty point in space more than a million kilometers away from Earth for the past 27 months. The spacecraft is to deploy the parachute two minutes after re-entering Earth's atmosphere.

The two chase helicopters will hover at 3000 meters, each prepared to be the one to intercept the parachute and its cosmic prize with a six-meter pole and hook.

The crews normally fly helicopter stunts for movies or help put out fires from above, but pilot Dan Rudert says this aerial fishing expedition is a unique challenge.

"It is an honor and also aviation history. This will actually be the first time a mid-air retrieval came in from outside the Earth's orbit," he says.

The package scientists are awaiting contains a large disk, about the size of a truck tire, that resembles a slice of a large beehive with dozens of six-sided sections.

The head of the U.S. space agency laboratory in California that operates the mission, Charles Elachi, says the unit has been deployed on the Genesis spacecraft, capturing high-speed, charged atomic particles blasted off the sun.

"We are going to bring a piece of the Sun down to Earth, and that is going to give us some fundamental understanding of our origin," he says.

NASA scientist David Lindstrom says the information the atoms provide about the solar system's origin will be different from that offered by space objects like meteorites or the moon rocks brought back by Apollo astronauts in the 1960s and 1970s.

"What we have been missing is the composition of the sun, which, after all, makes up 99 percent of the solar system. So this is what Genesis gives us, samples of the sun. These samples will allow precise measurements of the abundances of the elements and the isotopes in our solar system," Mr. Lindstrom adds.

The Genesis samples will be sent to laboratories around the world to be studied in ultra-clean rooms to avoid earthly contamination. The principal scientist for the project, Donald Burnett of the California Institute of Technology, says the analysis will be unprecedented in its technical scope.

"This is analysis at levels in many cases which has not been done before, and so we have had to develop our own new class of analytical instruments to do this," he says. " the world science community and the Genesis science team in particular has stepped up to enhance the capabilities to do this."

The helicopter pilots who must capture the samples say hooking the parachute from the Genesis spacecraft is a very difficult maneuver. If they fail, the capsule containing them will hit the desert at a speed of about 14 kilometers per hour with potentially damaging results.

"We do not know what the damage would be," this is George Carlisle, the chief navigator for the Genesis spacecraft. "If it lands on a perfectly smooth, sandy spot, it most likely would cause little to no damage. But if it landed up against the base of one of the many mountains that are out there and it ran into something hard, it could hit with tremendous impact and really wreak havoc with all the samples."

But if all goes well with the Genesis sample capture, project officials say the first scientific results could be out in six months

David McAlary, VOA News, Washington.

注释:
helicopter 直升机
parachute 降落伞
cosmic 宇宙的
retrieval 挽救
resemble 象,类似
beehive 拥挤的场面
meteorite 陨星
isotope 同位素
contamination 污染
maneuver 技术动作
capsule 太空舱
tremendous 极大的