A SHORT-WAVELENGTH MEASUREMENT OF THE COSMIC BACKGROUND-RADIATION ANISOTROPY

We report the results of a measurement of the CBR anisotropy at wavelengths between 0.4 and 2 mm, carried out using a balloon-borne 1.2 m telescope. We observed a high Galactic latitude region about 15° wide with a 25′ FWHM beam, switching in the sky with an amplitude of 108′. A sky signal correlated with the 100 μm diffuse emission mapped by the IRAS satellite was detected and used for calibration. After removal of this contribution, the residual intensity fluctuations give an upper limit to the anisotropy of the CBR at an equivalent frequency of 9.0 cm-1. We assumed Gaussian fluctuations with coherence angles between 5′ and 500′, and we found upper limits for ΔT/T ranging between 2.2 × 10-4 and 7 × 10-4 (95% confidence level).