Noise spectra throughout the mission lifetime for a 70 GHz radiometer 18M (left), 25S (44 GHz; middle), and 27M (30 GHz; right). Spectra are shown for the ranges from OD 100 (blue) to OD 1526 (red), spaced about 20 ODs apart. White noise is stable at the level of 0.3%, while low-frequency noise shows variations both in slope and knee-frequency, with different amplitude for different radiometers.