Abstract: A responsivity calibration system for use with an array of detectors. The system includes a first mechanism for changing the orientation of the detector array from the first orientation, during an operational mode, to a second orientation, during a calibration mode, in which each detector sequentially samples the same portion of the same scene. The system adjusts the output generated by each of the detectors in the first orientation in response to an associated signal generated by that respective detector in the second orientation. In a specific implementation, a normalization factor is generated based on the output of each detector during the calibration mode. The normalization factor is stored and multiplied by the outputs of the detectors during the operational mode. Hence responsivity correction is implemented without the need for a wide area scene of extreme uniformity or an on-board target.