A DEGREE-SCALE MEASUREMENT OF ANISOTROPY OF THE COSMIC BACKGROUND-RADIATION

We report on the preliminary result of a search for anisotropy in the cosmic background radiation (CBR) with a beam size of almost-equal-to 1.5-degrees FWHM over a wavelength range of 8-12 mm. The system operated successfully for 500 hr at the South Pole during the 1990-1991 austral summer. The data from one region, representing 25 hr after editing, are presented here. A strong signal is present in the lower frequency channels with a spectrum unlike CBR fluctuations, and is probably due to foreground emission. The highest frequency channel has the smallest contribution from this signal and has been used to set a 95% confidence level upper limit of DELTAT/T less-than-or-equal-to 1.4 x 10(-5) for fluctuations with a Gaussian autocorrelation function at a coherence angle of 1.2-degrees. This is significantly more sensitive than previous experiments at this angular scale.