Four noise sources occurring in an earth-viewing staring mosaic sensor mounted in a satellite are discussed. The four noise sources are (1) the internal system noise (detector and CCD), (2) the photon noise due to the background radiance level, (3) the noise due to background spatial characteristics scanned by an instability of the satellite, and (4) the noise due to the background temporal variations caused by cloud movement, solar movement, and scintillation. These four noise sources are affected by the particular sensor and their effect at the output of a sensor normally requires extensive calculations. A method of estimating bounds for each noise is demonstrated. This is done by approximating the actual functions by means of log-amplitude (Bode) plots.