Time evolution of the sub-band T_b differences of the time series at location A at the different angular resolutions. (a) T_b difference between sub-bands 3.1 and 3.4 at the original resolution (solid red line) and at the degraded resolutions corresponding to array configurations C3, C4, C5, and C6 (coloured dotted lines). (b) T_b difference between sub-bands 6.1 and 6.4 at the original resolution (solid blue line) and at the degraded resolutions corresponding to array configurations C3, C4, and C5 (coloured dotted lines). The horizontal dotted black lines show the level of ΔT_b = 0.