A MEASUREMENT OF THE ANGULAR POWER SPECTRUM OF THE ANISOTROPY IN THE COSMIC MICROWAVE BACKGROUND

We report on a measurement of the angular power spectrum of the anisot ropy in the cosmic microwave background (CMB). The anisotropy is measu red in 23 different multipole bands from l = 54 (approximate to 3 degr ees) to l = 404 (approximate to 0 degrees.45) and in six frequency ban ds from 26 to 46 GHz over three observing seasons. The measurements ar e consistent from year to year. The frequency spectral index of the fl uctuations (measured at low l) is consistent with that of the CMB and inconsistent with either dust or Galactic free-free emission. Furtherm ore, the observations of the MSAM1-92 experiment (Cheng et al. 1994) a re repeated and confirmed. The angular spectrum shows a distinct rise from delta T-l drop [l(2l + 1)[\a(l)(m)\(2)]/4 pi](1/2) = 49(-5)(+8) m u K at l = 87 to delta T-l = 85(-8)(+10) mu K at l = 237. These values do not include an overall +/-14% (l sigma) calibration uncertainty. T he analysis and possible systematic errors are discussed.