The analysis of radiometric relations is a basic requirement for the performance evaluation of any detection system. The CiNeRaMa (Contrast-to-Noise Ratio Model) presents a tool for system assessment at many engagement scenarios including different targets, atmospheric properties, and electro-optical sensors. The model determines the contrast-to-noise ratio (CNR) of small targets which depends on the detailed parameters of the particular scenario and in general cannot be expressed analytically. The model uses simplified target and sensor models together with radiative transfer calculations using LOWTRAN-7 code. The model incorporates a novel background clutter definition as the function of pixel size divided by the background correlation length and predicts the effects of cognitive screening of the clutter by a human observer. The rms pixel clutter is defined using background power spectral density, sensor resolution, and sensor-to-background distance. The proposed metrics might be useful in the thresholding of background clutter in image processing. The resulting contrast ofthe target above the clutterthreshold is compared with the electronic detector noise. The radiometric results of a typical engagement scenario can be employed for sensitivity analyses of sensor design.