Spacecraft Will Bring Bits of Sun
Jul 10 2001 @ 03:24
A robotic explorer named Genesis is about to embark on an unprecedented journey to gather and bring back bits of the sun.CAPE CANAVERAL, Fla. (AP) - NASA hopes the specks of solar wind - equivalent to perhaps 10 grains of salt, if added up - will help explain what it was like in the beginning. The very beginning, when the planets in the solar system were forming.
The amount of solar loot coming back is ``not much,'' admits project manager Chet Sasaki. ``But it's very valuable,'' he observes with a smile as his spacecraft undergoes another round of electrical checks at Kennedy Space Center.
On track for a July 30 launch, Genesis will be the first U.S. spacecraft since the Apollo moon ships to return samples from outer space.
And what a dramatic return it should be.
On Sept. 8, 2004, the UFO-like capsule containing the solar wind particles will glide down over the Utah desert by parafoil and be caught in midair by a helicopter. The capsule will be lowered gently to the ground by the helicopter and rushed to the same building that houses moon rocks at Johnson Space Center in Houston. Then the years of analysis will begin.
The idea of bringing the solar samples back in such an unusual, flashy way ``raised a lot of eyebrows in the beginning,'' says Genesis lead scientist Don Burnett, a geochemistry professor at the California Institute of Technology.
``But, in fact, it's turned out to be one of our least concerns,'' he says of the helicopter grab. The project team has tested the procedure and ``in all the tests, they got it the first time,'' he said.
The climactic finale has nothing to do with public relations, insists Burnett, who has been planning a solar sample mission for 18 years.
``This is driven by science considerations,'' he says. ``The materials in there are fairly fragile, and we have some fragile instruments we want to recalibrate. So we don't want this thing hitting the ground.''
Everyone working on the project can't wait until that that day.
Notes mission systems engineer Richard Bennett: ``Not only are we going out and sort of looking at the primordial essence of the universe, trying to bring back samples of that, that stuff we're pulling off the sun. But secondly, I think a very interesting part about the mission is the midair capture.''
The excitement in Bennett's voice is palpable as he shows off Genesis. A blue light in the huge, sterile room blinks, indicating the spacecraft systems are powered on for testing. The canister that will hold the solar samples, sealed since November to avoid contamination, is now being purged with nitrogen gas to keep the interior as clean as possible.
Deep inside the 5-foot-diameter sample return capsule are five round collector panels, each one resembling the side of a waffle iron. Each panel has rows of hexagon-shaped wafers made of ultra-pure silicon, diamond, sapphire, gold, aluminum or germanium, all of which will serve as, basically, flypaper.
As the solar wind streams past Genesis at more than 1 million mph, 92 million miles from the sun, microscopic traces of chemical elements will become embedded in the materials on the collector panels. The goal is to capture all 83 naturally occurring elements over 21/2 years, one atom at a time.
These castaway elements are the same material as the original solar nebula, the disk of gas and dust from which all the planets and other solar system objects formed 41/2 billion years ago. The outer layers of the sun, continually streaming into space as solar wind, provide the most feasible way to access this fossil record.
``If we could, we'd go there and scoop up that stuff. But we can't,'' says Sasaki, the project manager from the Jet Propulsion Laboratory in Pasadena, Calif.
Geochemist Burnett expects the equivalent of 1,000 grains of salt to be embedded in the panels when Genesis returns - on the order of milligrams. All but 10 grains will be hydrogen and helium, so common as to be of little interest. Those 10 precious grains - in the form of atoms spread uniformly over the collector panels - will be subjected to chemical analysis by scientists from around the world vying for a smidgen of the stuff.
``In truth, some elements are not worth as much scientifically as others, so we have priorities,'' Burnett says. Of keenest interest: oxygen, nitrogen and the noble gases, such as neon, argon, xenon and krypton.
The Apollo moonwalkers proved the concept of capturing solar-wind particles, from 1969 through 1972. They stuck poles holding sheets of aluminum foil in the lunar surface and brought them back along with their cache of moon rocks. The foil, while rudimentary, collected helium and neon particles from the solar wind.
NASA's Discovery program of low-cost science spacecraft is allowing Burnett to finally go after everything else blowing in the solar wind. The Genesis mission cost a relatively modest $259 million and was put together in just three years.
``There has been a perception which goes back from the post-Apollo time that sample-return missions were prohibitively expensive. You couldn't afford to do them,'' Burnett says. ``They were thinking of Apollo. They were thinking of men picking up rocks.''
The Discovery program, with its focus on robotics, changed that thinking.
NASA's Stardust spacecraft was launched in 1999 to collect and return comet dust. It's due back in January 2006.
Genesis will beat Stardust back by 11/2 years because it doesn't have nearly as far to travel, just to an invisible point 1 million miles from Earth toward the sun. It will take three months for Genesis to reach this point, where it will orbit for 21/2 years. The return trip should take six months.
The capsule containing the solar-wind particles will separate from the rest of the spacecraft four hours before touchdown. The spacecraft bus will re-enter the atmosphere over the Pacific, burning up. The capsule, meanwhile, will come down over the Utah Test and Training Range, a vast military installation in the remote desert bordering Nevada. First, a parachute will pop out, then the parafoil.
``The great thing about this, it's a one-time mission. We don't have to fly it many times,'' project manager Sasaki says. ``We bring the stuff back and this is going to last us a long time.
``While they may appear to be very small amounts, the fact is that the materials we collect we expect to last for 100 years.''
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