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CMB observations by [[*Planck*]{}]{} will proceed in great circles fixed on the ecliptic poles. A single scan will start at the North ecliptic pole, will follow a meridian to the South ecliptic pole and back to the North ecliptic pole by following the antipodal meridian. Such a scan will last one minute and will be repeated sixty times. After that, the rotation axis will be shifted in a precessional motion for $2\farcm5$ (approximately half a beam diameter) and the scan repeated. In this way, the entire sky is mapped once in 180 days.

Fourier transform of the noise time series of [[*Planck*]{}’s ]{}receivers yields a noise power spectrum $P(f)$ of the shape $$P(f) = \sigma_\mathrm{N}^2\cdot\left[1 + \left(\frac{f}{f_\mathrm{knee}}\right)^{-\alpha}\right]\mbox{,}$$ i.e. the noise consists of two components: a power law component in frequency $f$, decribed by the spectral index $\alpha$ that assuming values $0\leq\alpha\leq 2$ and a white noise component, smoothly joined at the frequency $f_\mathrm{knee}$.

The $f^{-\alpha}$-part of the noise spectrum originates from zero point drifts of the detector gain on large time scales. This power law component exhibits low-frequency variations that lead to the typical stripe pattern in simulated [[*Planck*]{}]{}-maps due to the scanning strategy . Algorithms for destriping the 