An approach is presented to estimate and minimize registration error between an optical or infrared imaging sensor and a nonimaging radar in a coboresighted multi-sensor object acquisition system. Previous efforts have been concentrated on analyzing the registration error between the sensed image and the reference image or between the same type of sensor signals. In this paper, models are developed for the centroid estimation error of an object from each sensor and for the registration error. The mean-square registration error is defined as a function of the sensor parameters and characteristics of the imaging sensor and the centroid uncertainty and pointing error of a monopulse radar. The optimal calibration range is estimated in terms of the sensor parameters and calibration object dimension.