Evolution of noise spectra over the mission lifetime for radiometer 18M (70 GHz, top), 25S (44 GHz, middle), and 27M (30 GHz, bottom). Spectra are colour-coded, ranging from OD 100 (blue) to OD 1526 (red), with intervals of about 20 ODs. White-noise levels and slope stability are considerably better than in the 2015 release, being at the 0.1% level for noise, while knee-frequencies show variations at the 1.5% level.