This paper presents the first prototype of a new method –called Heliosat-4– for assessing solar surface irradiance. The Heliosat-4 method is based on the radiative transfer model libRadtran and benefits from advanced products derived from recent Earth Observation missions. It will provide direct and diffuse components and spectral distribution of solar surface irradiance every 3 km and ¼ h over Europe and Africa. The outcomes of this first prototype of the method are compared to ground measurements made at 8 stations in Europe and Northern Africa. The results show that RMSE attained by the Heliosat-4 method is fairly similar to that attained by current methods. A large overestimation is observed. Nevertheless these tests are very encouraging.