Abstract: A real time method of rectifying remotely sensed image data provided by a radiation measuring instrument, such as used on spin stabilized geostationary satellites, rectification being obtained by determining a number of satellite parameters including radiation measuring instrument pointing parameters, the method comprising the following steps:1) prediction of the rectification parameters by statistical analysis from a number of preceding images;2) reading a limited number of raw image lines to facilitate accurate position of the South or North horizon, depending on scan direction of the incoming image;3) determining the spin rate of the satellite from the limited number of raw image lines and predicting the spin rate variations for the rest of the image;4) refining the attitude and the radiation measuring instrument pointing parameters using the horizon information obtained in real time;5) computing the position of the other horizon and the center of the image based on the first detected horizon and geometric