The Space Dynamics Laboratory at Utah State University (SDL/USU) calibrated the spatial infrared imaging telescope (SPIRIT) radiometer as part of its contract with the Ballistic Missile Defense Organization (BMDO). During the calibration effort, SDL/USU discovered and characterized a phenomenon that reduces the detector dark offset and responsivity after saturation, which results in increased calibration uncertainties directly following a saturation event. The magnitude and recovery duration for the dark offset and responsivity depend on several variables, including saturation flux level, saturation integration mode, integration mode, focal plane temperature, and saturation duration. Detector-to-detector variations in the magnitude of the saturation effect were also observed for detectors within an array. This phenomenon and the methods used to characterize it are described.