of redundant receivers per channel, because they provide independent surveys of the microwave sky.

From simulated scanning paths it is possible to derive an exposure map using the [simmission]{}- and [ multimod]{}-utilities. An example of such an exposure map in the vicinity of the North ecliptic pole is given in Fig. \[figure\_exposure\_map\]. Using the number of observations $n_\mathrm{obs}$ per pixel, it is possible to scale down the noise amplitudes by $\sqrt{n_\mathrm{obs}}$ and to obtain a realistic noise map for each channel. Here, we apply the simplification that all detectors of a given channel are arranged collinearly. In this case, the exposure maps will have sharp transitions from well-observed regions around the ecliptic poles to the region around the ecliptic equator. In real observations these transitions will be smoothed out due slight displacements of the optical axes among each other which causes the effective exposure pattern to be a superposition of rotated and distorted single-receiver exposure patterns.

Foreground emission components {#sect_foreground}
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The observation of the CMB and of SZ-clusters is seriously impeded by various Galactic foregrounds and by the thermal emission of celestial bodies of our Solar system. In order to describe these emission components, template maps from microwave surveys 