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Editor
Mike Hollis
Associate Editor
Jarrett Cohen
Consultants
Lara Clemence
Jim Fischer
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Pamela Ricks
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DeAnna Yu
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+ CISTO News Winter-Spring 2008
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ISSUE FOCUS ON HELIOPHYSICS |
NCCS Support of Space Exploration:
Improving Space Weather Modeling Required for
Interplanetary Travel
By Jarrett Cohen and Mike Hollis
Introduction
Within the next two decades, NASA will build
a new generation of vehicles to return to
the Moon and eventually make humankind’s
first trip to Mars. The Vision for Space
Exploration is the driver for this overarching
endeavor. Modeling and predicting the weather
of the space environment that intrepid astronauts
must traverse is a prerequisite for these
journeys.
“If NASA plans to explore the Moon
and Mars, reliably predicting space weather
is
essential,” said Tom Moore, Deputy
Director of the Heliophysics Science Division
at Goddard Space Flight Center (GSFC).
“If you were mounting an expedition
to Antarctica, you would ignore the weather
conditions at your peril. The solar system
is the same, only worse. There are all
kinds of powerful things going on in it.”
Among the hazards space travelers face
are potentially lethal proton radiation
events that emanate from solar storms.
For example, Figure 1 shows radiation
events during the Apollo missions to the
Moon in terms of ionizing radiation dosage
measured in Roentgen Equivalent Man (REM-the
deposition of about 94 ergs of energy
in 1 gram of soft body tissue). The radiation
events are shown as orange, green, and
pink bars. As established by the U.S.
Nuclear Regulatory Commission for occupations
in the nuclear field, the accumulative
total dosage for an adult worker should
not exceed 5 REM per year to be safe.
Note that this limit does not nor cannot
apply to astronauts! In any case, short,
high-radiation events are more lethal
than events of the same accumulated dosage
spread out over a longer time span. |
Figure
1: The graph shows the radiation dose
to astronauts from solar events during
the Apollo era missions, plotted against
sunspot count. With longer-duration space
flights planned as part of the Vision
for Space Exploration, sporadic risks
will become certain events. Figure from
NASA''s The New Science of the Sun-Solar
System Connection: Recommended Roadmap
for Science and Technology 2005–2035.
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As Figure 1 shows, the
astronauts were very lucky that most of
their missions did not coincide with major
solar events. An August 1972 event–right
between the Apollo 16 and 17 missions–would
have hit an astronaut with 300 to 3,000
REM of radiation!
Note that 400 to 450 REM of whole body radiation in a short period of
time would result in severe radiation poisoning and a 50 percent chance of fatality within 30 days. "It is mind-boggling
that they were that close," Moore said.
With a Mars journey taking months in each
direction, NASA must have the capability
to predict dangerous events and then provide
safe haven for astronauts within the spacecraft.
NASA has a fleet of spacecraft designed
to observe solar phenomena and space weather
(see Figure 2). Moreover, the NASA Center
for Computational Sciences (NCCS) is playing
a vital role in the advancement of space
weather modeling, which is really just
in its infancy. With the problem ultimately
involving the entire solar system, "we
need all the supercomputing facilities
that can be marshaled towards it, and
there is probably no limit to the computing
capability you could use," Moore said.
The CISTO News staff interviewed three
GSFC researchers heavily involved in improving
various aspects of space weather modeling:
- In the near vicinity of the
Sun, Joachim Schmidt investigates coronal
mass ejections and their measurable
effects at radio wavelengths using observations
from spacecraft and ground-based telescope
arrays.
- Inside the tail of Earth's magnetosphere,
Alex Klimas models the evolution and
interaction of magnetic reconnection
sites in the plasma sheet–phenomena
that can accelerate energetic particles
towards our planet.
- Still closer to Earth, Tom Moore
simulates the magnetosphere and ionosphere
as they react to the solar wind and
complicated solar events.
When perfected in NCCS exploratory runs,
their techniques will migrate to production
runs on the GSFC Space Weather Laboratory's
computing cluster and improve predictions
for the operational community. As they make
progress, these computational explorers
find that the NCCS is central to their research
efforts. In the words of Moore, "We really
treasure the NCCS!" |
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Figure 2: A fleet
of spacecraft observe phenomena that emerge
from the Sun and cause space weather.
Data from these spacecraft aid NASA scientists
using the NASA Center for Computational
Sciences to improve space weather modeling.
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Introduction
Part I: Simulating
Coronal Mass Ejections
Part II:
Focusing on Magnetic Reconnection
Part III:
Getting the Ionosphere Model Right
Epilogue
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http://www.nccs.nasa.gov
http:/hsd.gsfc.nasa.gov
http://nasascience.nasa.gov/heliophysics/mission_list |
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