Degree Angular Scale Interferometer
| Organisation |
CARA Centre for Cosmological Physics, University of Chicago Office of Polar Programs, National Science Foundation, US |
|---|---|
| Location(s) | Martin A.Pomerantz Observatory, Amundsen–Scott South Pole Station, Antarctica |
| Coordinates | 90°00′S 139°16′W / 90°S 139.27°WCoordinates: 90°00′S 139°16′W / 90°S 139.27°W |
| Altitude | 2,800 m (9,200 ft) |
| Weather | Clear with occasional blizzards |
| Wavelength | 26–36GHz |
| Built | Installed during 1999–2000 austral summer |
| Telescope style |  , Altazimuth mount 
|
| Diameter | 20cm elements x 13 |
| Angular resolution | Primary beam 3.4°, Synthesized beam 22' (0.37°) |
| Website | astro |
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The Degree Angular Scale Interferometer (DASI) was a telescope installed at the U.S. National Science Foundation's Amundsen–Scott South Pole Station in Antarctica. It was a 13-element interferometer operating between 26 and 36 GHz (Ka band) in ten bands. The instrument is similar in design to the Cosmic Background Imager (CBI) and the Very Small Array (VSA). In 2001 The DASI team announced the most detailed measurements of the temperature, or power spectrum of the Cosmic microwave background (CMB). These results contained the first detection of the 2nd and 3rd acoustic peaks in the CMB, which were important evidence for inflation theory. This announcement was done in conjunction with the BOOMERanG and MAXIMA experiment. In 2002 the team reported the first detection of polarization anisotropies in the CMB.
In 2005, the vacant DASI mount was used for the QUaD experiment, which was another CMB imager focussed on the E-mode spectrum. In 2010, the DASI mount was again repurposed for the Keck Array, which also measures CMB polarization anisotropy.
The CMB was created when the universe was about 380,000 years old, when the opaque plasma fog which existed after the Big Bang began to recombine into hydrogen atoms and allowed photons to travel freely through space. This radiation has since been redshifted by the expansion of the universe and can be seen faintly in the microwave part of the electromagnetic spectrum. In 1992 it was observed that there are very slight anisotropies in the effective temperature of the CMB, and the DASI telescope was outfitted to precisely measure these temperature anisotropies and then to detect polarization; the first to look at the polarization of the CMB. The ΛCDM (dark energy and cold dark matter) theory, regarded as the standard model of cosmology, predicted polarization of the CMB due to the scattering effects of the first atoms in the universe. Project leader John Carlstrom said that if polarization had not been found, astrophysicists would have to reject all their interpretations of recent data.
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