Visualisation of the input information used for the simulations (see Sect. 4.1 for more details). Upper row: panels a)-c), hit maps obtained for the grid-like, small circle, and big circle scans, respectively. Bottom row: d) noise correlations assumed for the stationary intervals and corresponding to different values of the knee frequency f_knee, (the diagonal, highly dominant element is not shown to emphasise the off-diagonal correlations), e) an example of the total intensity map of the CMB fluctuations.