Characterization of fixed-pattern noise is an important aspect in evaluating the performance of a staring array. The usual method of quantifying the effect of this artifact on the image is to state the variance of the pixel levels. However, this implicitly assumes that the fixed-pattern noise is spatially "white", that is, it has an equal effect at all spatial frequencies of interest. Usually, fixed-pattern noise has a nonrandom spatial distribution, which violates the assumption of white noise. A more complete characterization is provided by the spatial power spectrum of the fixed-pattern noise. This descriptor quantifies the effect of fixed-pattern noise on image data, both in terms of its frequency content, as well as its magnitude. Consideration of the noise spectrum is seen to yield additional insight into the nature of the fixed-pattern noise present on the array.