INFLUENCE OF GALACTIC DUST ON THE ACCURACY OF COSMIC MICROWAVE ANISOTROPY MEASUREMENTS

We have derived the power spectrum of Galactic dust emission by simula ting cosmic background experiments on IRAS maps. We have found that th e power index depends on the amount of dust, ranging from -3 (moderate ly clean regions, like the north celestial pole) down to -2 (the Lockm an Hole) or less (the cleanest regions, in the southern hemisphere). T herefore, for very low backgrounds, like those found in the cleanest d ust regions, the spurious anisotropies produced by dust tend to decrea se with the beam size, up to 10 degrees-20 degrees. For larger angular scales, the Galactic noise increases again. For moderate backgrounds, the spurious anisotropies have a flat spectrum or increase with the b eam size. These results have been used to design an optimized cosmic b ackground radiation (CBR) experiment in the far-infrared. Significant contamination in CBR anisotropy measurements is expected for wavelengt hs shorter than 1 mm, at both small and large angular scales. A cleani ng technique is suggested based on the use of a ground telescope opera ting through the millimetric atmospheric windows with an angular resol ution of similar to 5'.