Observations carried out from an Alpine location (3500 m) using a Dicke-type radiometer with a broad-band germanium bolometer have proved that the cosmic background radiation in the 900-1400-micron band can be measured from mountain altitudes with a precision comparable with that obtained in the 3.3-mm band. The inaccuracy in the measurements is attributed to calibration rather than to the atmospheric disturbances. The upper limit of 2.7°K observed is more stringent than that of previously reported balloon-borne and rocket-borne observations in the same band.

• Received 30 October 1974

DOI:https://doi.org/10.1103/PhysRevD.13.1187