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Aeronomy and Astrophysics

Center for Astrophysical Research in Antarctica (CARA)

John Carlstrom, University of Chicago.

Astronomers probe the infrared (IR) spectrum at submillimeter scales in search of data that could suggest answers to some of the seminal questions about the formation of the Universe; such as:
How do stars form from interstellar gas?
How did the planets form?
What was the nature of primeval galaxies?
How were matter and energy distributed in the early Universe?

Antarctica is an ideal spot for such research. The cold temperatures and lack of water vapor in the atmosphere above the polar plateau make the infrared spectrum of sky in that region consistently clearer and darker than anywhere else on Earth. These conditions enable scientists to collect measurements that would be extremely difficult or impossible from other sites. To capitalize on these advantages, the University of Chicago and several other collaborating institutions in 1991 established the Center for Astrophysical Research in Antarctica (CARA), one of 17 Science and Technology Centers funded by the National Science Foundation. CARA's scientific mission is to investigate the conditions for astronomy at the South Pole and other sites on the polar plateau, and to establish an observatory at the South Pole. Currently, CARA supports research using three major telescope facilities:

The Astronomical Submillimeter Telescope/Remote Observatory (AST/RO) project uses a 1.7-meter (m) diameter telescope to survey interstellar gas in the galactic plane, the galactic center, and the Magellanic Clouds.

The South Pole Infrared Explorer (SPIREX) project uses a 0.6-m diameter telescope to observe distant galaxies, cool stars, and heavily obscured star-forming regions.

The Cosmic Background Radiation Anisotropy (COBRA) project helps researchers test current theories of the origin of the Universe.

In addition to projects using these three telescopes, CARA's Advanced Telescopes Project collects data on the quality of polar plateau sites for astronomical observations, and configures plans for future telescopes and facilities. The following projects and principal investigators are currently part of CARA: (AC-370-O)

Antarctic Submillimeter Telescope and Remote Observatory (AST/RO):
This austral summer, we will install a new array receiver called PoleSTAR, which will permit high frequency (809 GHz) spectral line observations in four spatial channels simultaneously. We will use PoleSTAR to map emissions from excited carbon atoms and carbon-monoxide molecules in interstellar clouds. To characterize the properties of the polar atmosphere at far-infrared and submillimeter wavelengths, we also will install a broadband Fourier Transform Spectrometer in the AST/RO building. Antony Stark, Smithsonian Institution. (AC-371-O)

Automated Astrophysical Site Testing Observatory (AASTO):
Our objective is to categorize those conditions on the antartic plateau, from the ultraviolet to the sub-millimeter, that are relevant to a future large telescope. This season we will extend our sky monitors to the mid-infrared and sub-millimeter ranges, and continue our measurements of the atmospheric turbulence and the sky emission in the near-infrared. John Storey, University of New South Wales, Australia. (AC-372-O)

Degree Angular Scale Interferometer (DASI):
DASI is a 13-element interferometer designed to measure anisotropies in the Cosmic Microwave Background Radiation (CMBR), and to determine its angular power spectrum. The unique imaging capabilities of DASI and its angular coverage (140 < l < 910), complement the Viper telescope, especially its future millimeter and submillimeter capabilities (to be provided by ACBAR), as well as the MAP satellite and other CMBR experiments. John Carlstrom, University of Chicago. (AC-373-O)

South Pole Infrared Explorer (SPIREX):
The SPIREX telescope (60 centimeters in diameter) was built to exploit the unique observing conditions at the South Pole, and to develop and demonstrate the technology needed to operate IR telescopes during the antarctic winter. This austral summer, it will be dismantled and removed. Bob Lowenstein, University of Chicago. (AC-374-O)

Viper telescope:
Viper, a 2-meter class telescope, extends our observations to structures in the cosmic microwave background having smaller angular scales. Our primary goal is to determine the power spectrum of the CMBR anisotropy, over the range of angular scales where cosmological models differ most in their predictions. This austral summer we are refurbishing the telescope to allow for new cables and hoses for the ACBAR, Corona, and SPARO instruments. Also, we will raise the elevation of the telescope by about 4 centimeters, and install a new cable wrap, a new azimuth rind and new control wiring. Jeffrey Peterson, Carnegie-Mellon University. (AC-375-O)

Submillimeter Polarimeter for Antarctic Remote Observing (SPARO):
SPARO, which was deployed to the South Pole in 1999, operates on the Viper 2-meter telescope. A 9-pixel, 450-micron polarimetric imager, it requires only infrequent cryogen refills, thus simplifying maintenance during the winterover. The South Pole offers superb conditions for SPARO observations, extending submillimeter polarimetry (measurement of the polarization of thermal emission from magnetically aligned dust grains) to regions of low-column density that cannot be studied from other sites. SPARO resembles polarimeters in the University of Chicago array designed for other telescopes, but those instruments (for example, at the Caltech Submillimeter Observatory and the Owens Valley Radio Observatory) provide much better angular resolution. SPARO's geographic location, however, yields a much enhanced submillimeter sensitivity to extended emission. Giles Novak, Northwestern University. (AC-376-O)

Arcminute Cosmology Bolometer Array Receiver (ACBAR) Instrument:
We plan to install the ACBAR receiver on the Viper telescope, and get it ready for winter observations. ACBAR, a 16-element, 300 mK bolometer array, will be used to map the CMBR with high-angular resolution. We will try to characterize how the structure may have formed and evolved by searching for clusters of galaxies, and also will study nearby clusters with targeted observations. Preliminary observations and calibration will be done in the 2000-2001 summer season; the majority of the science data will be gathered during the 2001 winter. John Ruhl, University of California, Santa Barbara. (AC-378-O)

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