In-flight Geometric Calibration and Orientation of ALOS/PRISM Imagery with a Generic Sensor Model

Self-calibration is a powerful technique to exploit the geometric potential of optical spaceborne sensors. This paper explains the methodology of expanding a sensor model for in-orbit geometric calibration of the PRISM radiometers on the Japanese ALOS satellite. PRISM has three optical systems for forward, nadir, and backward views each with a 2.5 m nominal spatial resolution. Algorithms for the geometric processing of the PRISM images are proposed and implemented. It is shown how self calibration and orientation of the sensor can be done without having precise knowledge of the payload geometry and attitude data. Several cases and procedures are studied with the established sensor model, including weight matrices, attitude offsets, attitude drifts, and focal length estimations. It is concluded that self calibration of the PRISM cameras can be done effectively with a rigorous sensor model. Even if the post-launch parameters are not available, sub-pixel geometric accuracy can be achieved.