Systematic periodic Noise in image or Calibration Data which can be characterized in terms of frequency, phase and amplitude. It is often quantified using Fourier analysis. Coherent noise is usually electronic, coming from sources such as power supplies, transmitters, and clocks. It is desirable to remove, isolate or characterize sources of instrumental coherent noise before launch. It is possible to characterize signal-independent coherent noise most easily on dark background data such as night scenes. It is also visible in dark radiometrically homogeneous regions of a scene such as water. IF the coherent noise is well enough characterized and stable with time then it can be significantly reduced with notch Filtering using inverse Fourier transforms as a part of radiometric processing to produce the user