South Pole Telescope
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The South Pole Telescope or (SPT) is a 10 meter diameter telescope located at the South Pole Antarctica. It is a microwave telescope that observes in a frequency range between 70 and 300 GHz. The primary science goal for SPT is to conduct a survey to find several thousand clusters of galaxies, which should allow interesting constraints on the Dark Energy density and its equation of state.
The project is a collaboration between the University of Chicago, the University of California-Berkeley, Case Western Reserve University, the University of Illinois at Urbana-Champaign, the Smithsonian Astrophysical Observatory, the University of Colorado-Boulder, and McGill University. It is funded by the National Science Foundation.
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[edit] Microwave observations at the South Pole
The South Pole is the premier observing site in the world for millimeter wavelength observations. The Pole's high altitude (2.8 km above sea level) means the atmosphere is thin, and the cold temperatures keep the amount of water vapor in the air low. This is particularly important for observing microwaves, which are absorbed by water vapor. At the South Pole the sun sets in mid-March and is followed by six months of total darkness. During this time the atmospheric conditions become extremely stable without the added turbulence caused by the daily rising and setting sun, a phenomenon akin to reducing the amount of twinkling of stars in the sky.
[edit] The telescope
The telescope is a 10 meter off-axis Gregorian telescope in an altazimuth mount. It was designed to allow a large field of view (about 1 square degree) while minimizing systematic uncertainties from ground spill-over and scattering off the telescope optics. The surface accuracy of the telescope is better than 20 micrometers, which allows sub-millimeter wavelength observations. A key advantage of the SPT observing strategy is that the entire telescope is scanned, so the beam does not move relative to the telescope mirrors. The fast scanning of the telescope and its large field of view makes SPT efficient at surveying large areas of sky, which is required to achieve the science goals of the SPT cluster survey.
[edit] The camera
The focal plane for SPT is a 960 element bolometer array of superconducting Transition Edge Sensors (TES), which makes it one of the largest TES bolometer arrays ever built. The focal plane for SPT is split up into six pie-shaped wedges, each with 160 detectors. These wedges observe at three different frequencies: 90 GHz, 150 GHz, and 220 GHz. The modularity of the focal plane allows it to be broken into many different frequency configurations, however for the first year of observation two of the wedges observe at 90 GHz, three at 150 GHz, and one at 220 GHz. In the 150 GHz band, the array will be able image one square degree to about 30 microkelvins in about an hour.
[edit] Science goals
The first key project for the SPT will be a 4000 square degree survey to search for clusters of galaxies via variations in the cosmic microwave background radiation, based on the Sunyaev-Zel'dovich effect (SZE)[1]. Given three years of observing the South Pole Telescope should find several thousand clusters of galaxies, which should allow interesting constraints on the Dark Energy density and its equation of state.
The Atacama Cosmology Telescope has similar, but complementary, science objectives.
[edit] Current status
The South Pole Telescope achieved first light on February 16, 2007, and began science observations in March 2007. The telescope continues to observe throughout the austral winter, with winter-overers Stephen Padin and Zak Staniszewski at its helm.
[edit] References
- ^ A technique which has been successfully demonstrated using the Arcminute Microkelvin Imager and the Sunyaev-Zel'dovich Array
[edit] See also
[edit] External links
- http://pole.uchicago.edu/
- http://cosmology.berkeley.edu/group/swlh/sp_telescope/
- http://arxiv.org/abs/astro-ph/0411122
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