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.

In 2001 The DASI team announced the most detailed measurements of the temperature, or power spectrum of the cosmic microwave background (CMB).

The CMB was created when the universe was about 380,000 years old,[5] 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.

[8] The southern polar site is an exceptional location for this sort of telescope because of the extremely favourable atmospheric conditions.

[11] The telescope mount was of an altitude-azimuth (altazimuth) design, with a counterbalanced gear and pinion elevation drive, that gave great stability when tracking and pointing.

[8] The telescope was inside a large upside-down dome which served as a ground shield to minimise interfering thermal radiation from the earth.

[9] To avoid human exposure to the −60 °C (−76 °F) temperatures of the Antarctic winter, there was a canopy between the telescope and the ground shield which created a sealed cabin allowing access by ladder to the instruments without leaving the safety of the building.

[14] DASI made its first observations over 97 days during the 2000 austral winter, measuring temperature anisotropies of the CMB in 32 roughly adjacent circular areas of the sky, each 3.4° in diameter.

According to the theory, acoustic peaks are caused by the oscillations of matter during the Big Bang, which should be measurable as one main frequency or tone, with a series of overtones or harmonics.

From the more recent polarization results scientists could have "high confidence" of the presence of E-modes in the CMB, which added to the evidence supporting the ΛCDM Standard Model of Cosmology; the data is also helpful to understanding the mass distribution of the early universe.