We present measurements of anisotropy in the cosmic microwave background (CMB) from the first season of observations with the Degree Angular Scale Interferometer (DASI). The instrument was deployed at the South Pole in the austral summer 1999-2000, and we made observations throughout the following austral winter. We present a measurement of the CMB angular power spectrum in the range 100 < l < 900 in nine bands with fractional uncertainties in the range 10%-20% and dominated by sample variance. In this paper, we review the formalism used in the analysis, in particular the use of constraint matrices to project out contaminants such as ground and point source signals and to test for correlations with diffuse foreground templates. We find no evidence of foregrounds other than point sources in the data, and we find a maximum likelihood temperature spectral index ¼ À0:1 AE 0:2 (1 ), consistent with CMB. We detect a first peak in the power spectrum at l $ 200, in agreement with previous experiments. In addition, we detect a peak in the power spectrum at l $ 550 and power of similar magnitude at l $ 800, which are consistent with the second and third harmonic peaks predicted by adiabatic inflationary cosmological models.

The Degree Angular Scale Interferometer (DASI) has measured the power spectrum of the Cosmic Microwave Background anisotropy over the range of spherical harmonic multipoles 100 < l < 900. We compare this data, in combination with the COBE-DMR results, to a seven dimensional grid of adiabatic CDM models. Adopting the priors h > 0.45 and 0.0 ≤ τ c ≤ 0.4, we find that the total density of the Universe Ω tot = 1.04 ± 0.06, and the spectral index of the initial scalar fluctuations n s = 1.01 +0.08 −0.06 , in accordance with the predictions of inflationary theory. In addition we find that the physical density of baryons Ω b h 2 = 0.022 +0.004 −0.003 , and the physical density of cold dark matter Ω cdm h 2 = 0.14 ± 0.04. This value of Ω b h 2 is consistent with that derived from measurements of the primeval deuterium abundance combined with big bang nucleosynthesis theory. Using the result of the HST Key Project, h = 0.72 ± 0.08, we find that Ω tot = 1.00 ± 0.04, the matter density Ω m = 0.40 ± 0.15, and the vacuum energy density Ω Λ = 0.60 ± 0.15. (All 68% confidence limits.)

We present a formalism for analyzing interferometric observations of Cosmic Microwave Background (CMB) anisotropy and polarization data. The formalism is based upon the ell-space expansion of the angular power spectrum favoured in recent years. Explicit discussions of maximum likelihood analysis, power spectrum reconstruction, parameter estimation, imaging and polarization are given. As an example, several calculations for the Degree Angular Scale Interferometer (DASI) and Cosmic Background Interferometer (CBI) experiments are presented.Comment: 25 pages, 5 figures, minor changes to reflect final version accepted by Ap

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Measurements of the cosmic microwave background (CMB) radiation can reveal with remarkable precision the conditions of the Universe when it was approximately 400,000 years old. The three most fundamental properties of the CMB are its frequency spectrum (which determines the temperature), and the fluctuations in both the temperature and polarization across a range of angular scales. The frequency spectrum has been well determined, and considerable progress has been made in measuring the power spectrum of the temperature fluctuations. But despite many efforts to measure the polarization, detection of this property of the CMB has hitherto been beyond the reach of even the most sensitive observations. Here we describe the Degree Angular Scale Interferometer (DASI), an array of radio telescopes, which for the past two years has conducted polarization-sensitive observations of the CMB from the Amundsen-Scott South Pole research station.

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Observations of the microwave sky using the Python telescope in its fifth season of operation at the Amundsen-Scott South Pole Station in Antarctica are presented. The system consists of a 0.75 m offaxis telescope instrumented with a HEMT amplifier-based radiometer having continuum sensitivity from 37-45 GHz in two frequency bands. With a 0.91 • × 1.02 • beam the instrument fully sampled 598 deg 2 of sky, including fields measured during the previous four seasons of Python observations. Interpreting the observed fluctuations as anisotropy in the cosmic microwave background, we place constraints on the angular power spectrum of fluctuations in eight multipole bands up to l ∼ 260. The observed spectrum is consistent with both the COBE experiment and previous Python results. There is no significant contamination from known foregrounds. The results show a discernible rise in the angular power spectrum from large (l ∼ 40) to small (l ∼ 200) angular scales. The shape of the observed power spectrum is not a simple linear rise but has a sharply increasing slope starting at l ∼ 150. Subject headings: cosmic microwave background -cosmology: observations

The third year of observations with the Python microwave background experiment densely sample a 5.5° × 22° region of sky that includes the fields measured during the first two years of observations with this instrument. The sky is sampled in two multipole bands centered at l ≈ 92 and l ≈ 177. These two data sets are analyzed to place limits on fluctuations in the microwave sky at 90 GHz. Interpreting the observed fluctuations as anisotropy in the cosmic microwave background we find flat band power estimates of δ π T 54 12 14 l l