A BOLOMETRIC MILLIMETER-WAVE SYSTEM FOR OBSERVATIONS OF ANISOTROPY IN THE COSMIC MICROWAVE BACKGROUND-RADIATION ON MEDIUM ANGULAR SCALES

We report the performance of a bolometric system designed to measure the anisotropy of the cosmic microwave background (CMB) radiation on angular scales from 0-degrees-3 to 3-degrees. The system represents a collaborative effort combining a low-background 1 m diameter balloon-borne telescope with new multimode feed optics, a beam modulation mechanism with high stability, and a four-channel bolometric receiver with passbands centered near frequencies of 3 (90), 6 (180), 9 (270), and 12 (360) cm-1 (GHz). The telescope has been flown three times with the bolometric receiver and has demonstrated detector noise limited performance capable of reaching sensitivity levels of DELTA-T/T(CMB) almost-equal-to 10(-5) with detectors operated at T = 0.3 K.