Balloon-borne measurements of the atmospheric emission near 94 GHz

We report on a balloon-borne experiment to measure high altitude atmospheric emission in the 90 GHz spectral window. The experiment was carried out with a monolithic microwave integrated circuit (MMIC) Dicke-switched radiometer based on high electron mobility transistor (HEMT) low noise amplifiers. The instrument broad bandpass (87-101 GHz) includes strong ozone lines. The atmospheric emission profile was measured from 6 to 15 km altitude. In addition, zenith-scan measurements at about 38 km altitude have been obtained, yielding an atmospheric antenna temperature T-A,T-atm = 15+/-6 mK. The results are in good agreement with model predictions which take into account the contribution of O-3, spectral lines. Ozone emission contributes significantly to the signal of balloon-borne Cosmic Microwave Background experiments unless the instrument bands are carefully selected. (C) 1998 Elsevier Science Ltd. All rights reserved.