Los Alamos instruments to capture the sun

Three instruments designed and built
by researchers at the U.S. Department of Energy’s Los Alamos National
Laboratory will help scientists understand the origin of the solar system.

The instruments are aboard Genesis, a remote-controlled NASA space mission
designed to capture particles from the sun and return them to Earth. The
spacecraft is scheduled for launch on July 30 from Florida’s Cape Canaveral
Air Force Station.

Genesis will collect samples of the solar wind to reveal the makeup of the
cloud that formed the solar system nearly five billion years ago.

Scientists believe the solar system possibly began with a dense cloud of
gas and dust that collapsed in on itself. Most of this “solar nebula”
condensed to form the sun, while outlying particles coalesced into the
diverse planets, moons and comets that make up our solar system.

Although scientists have a general understanding of the formation of the
solar system, the composition of the initial nebula remains relatively
unknown. Fortunately, nature provides a record of the solar nebula; its
pristine composition is preserved for the most part in the outer layers of
the sun. The solar wind provides a continuous flow of this material into
space.

“To understand how the planets were formed with their different compositions,
we need to know the starting materials,” explains Roger Wiens, who led the
payload instrument development at Los Alamos.

Genesis’ main goal is to determine isotopic ratios of different elements in
solar matter, with a focus on oxygen — an element making up two thirds of
everything found on earth. Oxygen isotope amounts vary among the different
planets in the solar system and this puzzles scientists because all solar
system bodies were supposedly formed from the same raw materials. An isotope
is a variation of an element — it has more or fewer neutrons in its nucleus
making it heavier or lighter than the standard form of the element.

Los Alamos designed and built a solar wind concentrator to collect a high
concentration of oxygen and return the sample back to Earth for analysis.
The concentrator takes solar wind and passes it through a series of
electrically charged grids into a bowl-shaped mirror. The mirror reflects
a filtered stream of elements heavier than hydrogen upward into a centrally
poised collector tile, where oxygen and other elements embed themselves.

The several layers of charged grids are made of incredibly strong and
durable wires one-fourth the diameter of a human hair. The wire grids
possess different electrical charges to filter out the much more numerous
hydrogen ions and direct other ions of interest to the collector tile.

The collector tile, a four inch disk, is made of four pie-shaped pieces of
ultra-pure materials: one industrial diamond wedge, two silicon carbide
wedges and one wedge of silicon topped with thin diamond. The entire interior
of the concentrator is coated with a very thin layer of gold to keep all the
surfaces free of oxygen.

The surface of the concentrator’s bowl-shaped mirror was specially treated
to reflect the sun’s incoming light back out of the instrument to avoid
damaging the collector tile with focused sunlight.

“We used a solar simulation, initially a spotlight purchased from Hollywood,
to test how the concentrator will respond to sunlight in the vacuum of
space,” said Wiens. “During the test, we had to monitor the shapes of the
fragile grids. If the grids get any damage, like wrinkles, this could change
the path of the ions so that they don’t reach the collector tile and this
would give skewed results.”

“The concentrator is the first solar instrument sent into space that we will
ever see again,” said Beth Nordholt, of the Neutron Science and Technology
Group and one of the leaders on the concentrator instrument. “All other
instruments aboard spacecrafts remain in space indefinitely, or, like Lunar
Prospector, are intentionally crashed after their mission ends. This is the
first mission in three decades, since the Apollo missions in the seventies,
that will bring extraterrestrial samples back to Earth for analysis.”

The other two Los Alamos instruments aboard Genesis are solar wind ion and
electron monitors. Genesis’ ion and electron monitors instantaneously
determine which type of solar wind is passing the spacecraft at any time
and translate that knowledge into actions for the solar wind concentrator
and solar wind collector arrays — five meter-sized panels containing 55
coaster-sized tiles made of a variety of materials selected to trap
specific elements in the solar wind.

The monitors will distinguish between three types of solar wind by
recognizing their characteristic temperature, velocity, direction and
composition. The onboard computer will use the information collected by
the monitors to adjust the solar wind concentrator for optimum oxygen
concentration and to select the appropriate collector arrays for exposure
to the wind.

The ion monitor measures the density, temperature and energy of protons and
alpha particles — helium atoms stripped of their electrons — in the solar
wind. About 96 percent of the solar wind is composed of protons, 4 percent
alpha particles and less than 1 percent minor ions, one being oxygen.

Genesis’ electron monitor will determine the direction of travel of
solar-wind-electrons. Located on the edge of Genesis’ equipment deck, it
can view the whole sky as the spacecraft rotates.

Genesis will collect just 10 to 20 micrograms of solar wind — or the
equivalent of a few grains of salt. The extraterrestrial material will
return to Earth in 2004 — in the spacecraft’s specially designed sample
return capsule — for analysis.

The instruments were built in clean rooms to avoid terrestrial contamination
in order to guarantee the atoms analyzed are of pristine solar origin. They
were designed and constructed by a team of scientists and engineers from Los
Alamos’ Space and Atmospheric Sciences and Space Instrumentation groups under
the direction of Wiens, Nordholt, Bruce Barraclough, Donald Mietz, Eric Dors
and Daniel Reisenfeld.

Genesis is the first spacecraft to have a completely robotically-controlled
sample collection system in which data from science instruments is used to
control sample collection. The software to control the payload was developed
jointly by Los Alamos National Laboratory and the spacecraft builder,
Lockheed Martin Astronautics in Denver.

The mission is led by Donald Burnett, a professor in the Geology and
Planetary Science Division at California Institute of Technology, Pasadena,
and is managed by NASA’s Jet Propulsion Laboratory. The collector tile
portion of the payload was also built at JPL.

During flight, the entire payload will be under the control of Los Alamos
National Laboratory. Scientists will monitor the health of the payload
instruments and will keep a history of all solar wind conditions and array
exposure times. These data will be made available to the scientific
community at large.

Los Alamos National Laboratory is operated by the University of California
for the U.S. Department of Energy’s National Nuclear Security Administration.

EDITORS’ NOTE: Photographs for news use are available at
http://www.lanl.gov/worldview/news/gene