The techniques employed to evaluate the performance of conventional aerial imaging systems are extended to the evaluation of space imaging systems. The general concepts are illustrated by employing the Lunar Orbiter as an example. Quality parameters are selected, and methods for their measurements from the Lunar Orbiter imagery are described. Results from statistical communication theory are employed to relate system performance as determined by design objectives to the quality of the reconstructed image. The evaluation of the performance of the Lunar Orbiter I and II imaging systems based upon these results is described. One of the criteria describing the detectability of small objects on the lunar surface is shown to correlate with data obtained from visual inspection of the photographs by trained observers.