Influence of galactic dust on the accuracy of cosmic microwave anisotropy measurements

We have derived the power spectrum of Galactic dust emission by simulating cosmic background experiments on IRAS maps. We have found that the power index depends on the amount of dust, ranging from -3 (moderately clean regions, like the north celestial pole) down to -2 (the Lockman Hole) or less (the cleanest regions, in the southern hemisphere). Therefore, for very low backgrounds, like those found in the cleanest dust regions, the spurious anisotropies produced by dust tend to decrease with the beam size, up to 10 - 20 deg. For larger angular scales, the Galactic noise increases again. For moderate backgrounds, the spurious anisotropics have a flat spectrum or increase with the beam size. These results have been used to design an optimized cosmic background radiation (CBR) experiment in the far-infrared. Significant contamination in CBR anistropy measurements is expected for wavelengths shorter than 1 mm, at both small and larger angular scales. A cleaning technique is suggested based on the use of a ground telescope operating through the millimetric atmospheric windows with an angular resolution of approximately 5 arcmin.