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| DASI (experiment) | |
|---|---|
| Name | DASI |
| Caption | The DASI telescope at the Amundsen–Scott South Pole Station |
| Acronym | DASI |
| Established | 1999 |
| Location | Amundsen–Scott South Pole Station |
| Telescope type | Interferometer |
| Wavelength | Microwave (26–36 GHz) |
| Operator | California Institute of Technology, University of Chicago |
DASI (experiment)
DASI was a compact microwave interferometer deployed at the Amundsen–Scott South Pole Station to measure anisotropies and polarization in the Cosmic microwave background radiation. Designed and operated by a collaboration led by the California Institute of Technology and the University of Chicago, the project produced key detections that influenced studies at facilities such as BOOMERanG, WMAP, and Planck. Its results informed theoretical work associated with Big Bang nucleosynthesis, inflation (cosmology), and models developed by researchers at Harvard University and the Princeton Plasma Physics Laboratory.
DASI was conceived to measure the angular power spectrum and polarization of the Cosmic microwave background on degree and sub-degree angular scales, providing constraints complementary to those from the COBE satellite and the balloon-borne BOOMERanG experiment. The instrument targeted multipoles corresponding to acoustic peaks predicted by ΛCDM models and tested predictions from inflationary scenarios developed by theorists at the Institute for Advanced Study and Stanford University. Principal investigators included scientists formerly affiliated with Caltech, the University of Chicago, and the National Science Foundation Antarctic program. Data from DASI contributed to parameter estimation efforts performed by teams at Cambridge University, University of Oxford, and Max Planck Institute for Astrophysics.
DASI consisted of a 13-element, co-mounted interferometric array operating at 26–36 GHz, designed to probe degree-scale anisotropy and polarization with synthesized beams comparable to those produced by instruments at the Very Large Array and the Submillimeter Array. The array was sited at the Amundsen–Scott South Pole Station to exploit the low precipitable water vapor and stable atmospheric transmission used by observatories such as South Pole Telescope and BICEP. The cryogenic receivers and correlator electronics incorporated technologies developed at Jet Propulsion Laboratory, National Radio Astronomy Observatory, and the Kavli Institute for Cosmological Physics. The Antarctica location connected DASI to logistical support from United States Antarctic Program and engineering input from Lockheed Martin contractors.
DASI conducted observations during the 1999–2000 and subsequent austral winters, implementing a combination of daily drift scans and targeted fields coordinated with contemporaneous campaigns by BOOMERanG, MAXIMA, and ACBAR. Data acquisition employed a correlator architecture inspired by designs used at the Very Large Array and calibration schemes similar to those from the COBE team. Pointing and flux calibration referenced sources cataloged by ATCA and flux standards monitored by teams at Harvard-Smithsonian Center for Astrophysics. Data reduction pipelines drew on software methodologies from HEALPix developers, with map-making and power spectrum estimation routines paralleling work at CITA and MPIA.
DASI produced one of the first robust detections of CMB polarization, reporting E-mode polarization consistent with predictions from adiabatic perturbation models advanced by researchers at Cambridge University and Princeton University. Its measurement of the angular power spectrum corroborated acoustic peak structure measured by BOOMERanG and MAXIMA and informed cosmological parameter constraints used in analyses at WMAP and later Planck. The polarization detection provided empirical support for scattering physics described in texts by authors affiliated with University of Chicago and Columbia University and motivated theoretical follow-ups from groups at Yale University and MIT. DASI results were cited in policy and review contexts by panels convened at National Academy of Sciences and influenced funding priorities at the National Science Foundation and Department of Energy.
The DASI collaboration included scientists from California Institute of Technology, University of Chicago, University of California, San Diego, University of Wisconsin–Madison, and international partners from University of British Columbia and University of Cambridge. Support and oversight were provided by the National Science Foundation through the United States Antarctic Program, with instrument contributions and technical services from Jet Propulsion Laboratory, National Radio Astronomy Observatory, and industrial partners such as Raytheon. Analysis and publication efforts were coordinated with archives and computing resources associated with NASA and the European Space Agency.
DASI’s polarization detection and interferometric approach influenced subsequent experiments including QUaD, BICEP, Polarbear, and the South Pole Telescope polarimeter upgrades. Techniques refined by DASI teams fed into instrument designs at ALMA and algorithmic developments used by Planck data analysis groups. Alumni of the DASI collaboration went on to lead projects at Princeton University, Harvard University, Stanford University, and national laboratories such as Lawrence Berkeley National Laboratory and Fermi National Accelerator Laboratory. The experiment remains cited in reviews by the International Astronomical Union and educational materials at institutions like California Institute of Technology.