Inflight calibration of SPOT CCD detector geometry

The fact that the SPOT satellites carry two independent instruments offers a unique possibility to determine the detector position errors in the CCD arrays. By simultaneously imaging the same area with the panchromatic sensors in both instruments, detector errors in one instrument can be measured by comparison with the image from the other instrument. By repeating this measurement in other image pairs, with different displacements between images, a unique solution for the detector position errors in both instruments can be obtained. A method based on generalized inverse algebra is developed for this type of computation, and applied to the SPOT-1 satellite.