Dwayne Brown
Headquarters, Washington
202-358-1726
RELEASE: 07-123
NASA SPACECRAFT AIDS IN FORECAST OF SOLAR RADIATION STORMS
WASHINGTON - NASA's Solar and Heliospheric Observatory (SOHO) now
enables scientists to forecast solar radiation storms, giving future
astronauts, traveling to the moon and Mars, time to seek shelter and
ground controllers time to safeguard satellites. The new method for
the first time offers as much as one hour advance notice when a storm
is approaching.
"Solar radiation storms are notoriously difficult to predict. They
often take us by surprise, but now we've found a way to anticipate
these events," says Arik Posner, a physicist in NASA's Science
Mission Directorate, Washington. Posner is on temporary assignment to
NASA from Southwest Research Institute, San Antonio. Posner developed
the technique. His study appears in a recent issue of the journal
Space Weather.
Solar radiation storms are swarms of electrons, protons and heavy ions
accelerated to high speed by explosions on the sun. On Earth, humans
are protected from these particles by Earth's atmosphere and magnetic
field. Astronauts in Earth orbit also are protected since Earth's
magnetic field extends far enough to shield them. Solar radiation
storms are a potential risk factor for astronauts working on the
surface of the moon or Mars since neither has a substantial magnetic
field.
"A one hour warning would reduce the odds of being caught in a solar
storm outside of a lunar habitat, where astronauts are most
vulnerable," says Francis Cucinotta, chief scientist for the NASA
Space Radiation Program at NASA's Johnson Space Center, Houston.
Spacecraft and satellites would also benefit. Subatomic particles
striking computer processors and other electronics can cause onboard
computers to suddenly reboot or issue nonsense commands. If a
satellite operator knows that a storm is coming, the craft can be
placed in a protective "safe mode" until the storm passes.
The type of particle most feared by safety experts is the ion, an atom
that has lost one or more of its charge-balancing electrons.
Energetic ions can damage tissue and break strands of DNA, an effect
not fully understood in terms of human disease.
The goal of researchers is to forecast when the ions will arrive. "The
key is electrons. They are always detected ahead of the more
dangerous ions," says Posner. While this has been known for years,
only recently has this research turned the "electrons first" aspect
of radiation storms into a tool for forecasting.
Every radiation storm is a mix of electrons, protons and heavier ions.
The electrons, being lighter and faster than the others, race out
ahead. By measuring the "rise time and intensity of the initial
electron surge" Posner could predict how many ions were following and
when they would arrive.
The key to the breakthrough was the Comprehensive Suprathermal and
Energetic Particle Analyzer (COSTEP) instrument on board the
observatory. COSTEP counts particles coming from the sun and measures
their energies. Posner looked at hundreds of radiation storms
recorded by COSTEP between 1996 and 2002, and was able to construct
an empirical, predictive matrix that involved plugging an electron
data into the matrix, and an ion forecast emerging.
After testing the results, the matrix was used on COSTEP data gathered
in 2003, a year not yet analyzed and which formed no part of the
matrix itself. The matrix was applied to the electron data and as a
result, it successfully predicted all four major ion storms of 2003
with advance warnings ranging from 7 to 74 minutes.
"While the method is not yet perfect, I'd like to improve that,"
Posner says. Improvements will come as Posner works his way through
even more of COSTEP's dataset.
"Launched with SOHO in 1995, COSTEP has been operating through an
entire solar cycle including the recent solar maximum in 2001, and it
is still going strong," says Prof. Bernd Heber, COSTEP's principle
investigator at the University of Kiel, Germany.
The method is being considered by planners at the Johnson Space Center
in their design of future lunar missions. "Posner's technique reduces
the odds of exposure by more than 20 percent compared to current
methods, allowing astronauts to venture farther from their outpost.
That's good for both science and exploration," says Cucinotta.
"NASA's Vision for Space Exploration will lead humans away from
Earth's protective magnetic cocoon and into the unprotected seas of
outer space," says Posner. "New scientific knowledge concerning basic
processes of space will ensure safe, effective achievement of NASA's
future space exploration activities."
SOHO is a project of international cooperation between the European
Space Agency and NASA. For more information on NASA's study of the
solar system, visit:
http://www.nasa.gov/mission_pages/soho/index.html
-end-
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