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Astrophysics in Antarctica
Background
The National Science Foundation (NSF), through the U.S. Antarctic Program
(USAP), coordinates almost all U.S. scientific research in the Antarctic.
NSF is an independent federal agency responsible for providing support
for research in almost all fields of science and engineering.
The USAP's goals are: to understand the Antarctic and its associated
ecosystems; to understand the region's effects on (and responses to) global
processes such as climate; and to use Antarctica's unique features for
scientific research that cannot be conducted as well elsewhere.
Among the scientific disciplines encompassed by this broad mandate are
astronomy, atmospheric sciences, biology, earth science, environmental
science, geology, glaciology, marine biology, oceanography and geophysics.
Antarctic Astrophysics
A variety of conditions both in Antarctica generally and more specifically
at the South Pole make the continent a world-class observatory.
Long-Duration Ballooning (LDB): Since 1988 NSF and NASA have
developed techniques for flying and recovering large balloon payloads
-- in the range of two tons -- at altitudes of roughly 37 kilometers (120,000
feet) for extended periods of approximately two weeks. These techniques
position the experiment above 99.7 percent of the atmosphere. For some
experiments, this provides scientists with conditions as good as a ride
on the space shuttle or even a satellite.
For two reasons, the unique geophysical conditions above Antarctica
make LDB flights possible during the austral summer.
Since the balloon is illuminated continuously by sunlight, both directly
and by reflection from the underlying clouds or snow, it does not undergo
the large changes in temperature, and therefore altitude, that are experienced
during the normal diurnal cycle in more temperate regions. There, the
daily heating and cooling cycle results in the loss of helium and also
ballast, severely limiting flight times, a situation that is avoided above
Antarctica. Additionally, each summer for a period of a few weeks, a nearly
circular pattern of gentle east-to-west winds is established in the Antarctic
stratosphere. The circulation is generated by a long-lived high-pressure
area caused by the constant solar heating of the stratosphere. This allows
the launching and recovery of a balloon where it can be recovered relatively
easily on land.
Over the past decade there have been LBD flights in most Antarctic research
seasons -- roughly mid-December through mid-January, with two balloons
frequently being flown during the season.
South Pole Astrophysics: Several geophysical attributes make
Amundsen-Scott South Pole Station, operated by the USAP, an important
and unique observatory:
- Its location at the earth's axis means that any celestial object can
be observed for long periods from the same elevation in the sky. Most
famously, for many years South Pole was used to make long continuous
solar observations, with some runs lasting for over 100 hours.
- The station is located at an altitude of approximately 3,000 meters
(10,000 feet), atop the Antarctic ice sheet. The atmosphere at the station
also is extremely cold, with the result that there is very little water
vapor overhead. Water vapor is the principal cause of atmospheric absorption
and variability in broad portions of the electromagnetic spectrum from
the near infrared to millimeter radio waves. Many telescopes have exploited
this over the past decade, most notably to map submillimeter neutral
carbon emission in the galaxy and to measure the anisotropy of the cosmic
microwave radiation.
- The Antarctic Muon and Neutrino Array (AMANDA) takes advantage of
the extremely clear ice deep below the surface at South Pole to create
the world's largest particle detector. AMANDA can detect and track the
path of neutrinos that interact in the ice after having passed completely
through the earth. AMANDA is presently the only viable high-energy neutrino
telescope with over 500 photodetectors buried between 1,400 and 2,400
meters below the surface.
See also: Press
Release on Detailed Images of Early Universe
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