Astrophysics in Antarctica
November 22, 2004
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.
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
Peter West, NSF, (703) 292-8070, email: firstname.lastname@example.org
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