Sun Sample
Return Mission Nears Launch
NASA
Science News
The science payload for NASA's
Genesis spacecraft, which will collect samples of the
solar wind and return them to Earth, is now complete.
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October
12, 2000 -- NASA's Genesis spacecraft, the first mission
to collect and return samples of the solar wind, is
moving closer to launch. Scheduled for liftoff in
February 2001, Genesis will help scientists refine our
basic understanding of the Sun's characteristics, and
understand how the solar nebula, an interstellar cloud
of gas and dust, gave rise to our complex solar system
billions of years ago.
According to NASA's Jet Propulsion
Laboratory, which manages the mission for NASA's Office
of Space Science, the spacecraft has just received its
final piece of science equipment: a solar wind collector
made of bulk metallic glass, similar to materials found
in high-tech golf clubs. It and other solar wind
collector tiles on the spacecraft will gather the
first-ever samples of the solar wind as the spacecraft
floats in the oncoming solar stream outside Earth's
magnetosphere.
Above: The solar
wind streams away from the Sun in all directions.
NASA's Genesis spacecraft will travel 1.5 million
kilometers toward the Sun where it can sample the solar
wind from the L1 Lagrangian point.On its return to Earth
in 2003, samples collected by Genesis will be retrieved
in midair by helicopters and sent to laboratories for
detailed analysis.
Because the outer layers of the Sun
are composed of nearly the same material as the original
solar nebula, samples returned by Genesis will shed new
light on the chemical evolution of meteorites, comets,
lunar samples, and planetary atmospheres.
The body of the spacecraft contains a
canister with collector plates that fold out like blades
on a pocket knife to collect solar wind. Most of the
collectors are hexagonal silicon wafers, but one is
different. Capping the shaft on which the collector
plates rotate will be a disk about the size of a coffee
cup that is a unique formulation of bulk metallic glass
created especially for Genesis.
Left:
The Genesis science canister contains all the sampling
equipment for the science of the mission. When traveling
to and from the Earth, the canister is completely sealed
to prevent contamination. This photo shows the canister
in the fully open position that it will assume when it
reaches L1. Inside the lid and stacked inside the
canister are arrays of hexagonal silicon wafers. The
samples of solar wind particles will be returned to
Earth embedded inside these wafers.
In an odd mix of science and sports,
golfers and Genesis scientists both like bulk metallic
glasses, but for different reasons. Premium golf clubs
can be made with a kind of bulk metallic glass that is
hard but springy. Scientists use a type that absorbs and
retains helium and neon, important elements in
understanding solar and planetary processes.
The new bulk metallic glass-forming
alloy was designed by Dr. Charles C. Hays in the
materials science laboratories of Caltech. It is a
complex mixture of zirconium, niobium, copper, nickel,
and aluminum. The atoms of metallic glasses solidify in
a random fashion, unlike metals that have an ordered
crystalline structure. This disordered atomic state
makes metallic glasses useful in a wide range of
applications, from aircraft components to high-tech golf
clubs. The Genesis metallic glass was prepared in a
collaborative effort by Hays and George Wolter of the
Howmet Corporation, Greenwich, Conn., using the same
process the company uses for the high-tech Vitreloy-based
golf clubs.
The
surfaces of metallic glasses dissolve evenly, allowing
the captured ions to be released in equal layers by
sophisticated acid etching techniques developed by the
University of Zurich, Switzerland. Higher-energy ions
blast further into the metal's surface. When samples are
back on Earth, special techniques will be used to etch
the metal layer by layer, releasing the particles of gas
for laboratory study.
Above: The Genesis Mission's
bulk metallic glass solar wind collector.
"One exciting thing about bulk
metallic glass is that it will enable us to study ions
with energies higher than the solar wind. This allows
Genesis to test proposals that the higher energy
particles differ in composition from the solar
wind," said Burnett. This will be the first time
the theories about different kinds of solar wind can be
tested by bringing back actual samples, he said.
Below: A specially modified
helicopter with a boom and winch underneath snags the
parafoil chute attached to a model Genesis sample return
capsule. The hook on the end of the boom collapses the
chute, allowing the helicopter to retrieve the capsule
in mid-air. This is necessary to ensure the purity of
the solar wind samples inside. This photo was taken
during successful trials of this novel capsule recovery
technology.
To
bathe in the solar wind, the spacecraft only needs to
fly about 1.5 million kilometers (1 million miles)
toward the Sun (about 1 percent of the Sun-Earth
distance). When it is in the right position -- outside
of Earth's magnetic field, between Earth and the Sun
where the gravity of both bodies is balanced, called the
Lagrange point -- the capsule will open its collector
arrays and let ions barrage its panels.
Genesis is managed by JPL for NASA's
Office of Space Science, in Washington, DC. It is part
of NASA's Discovery Program of low-cost, highly focused
science missions. JPL is a division of the California
Institute of Technology.
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