Estimation - Global horizontal irradiance (GHI)- Meteorological satellites MSG- Heliosat-2 - Cloud index n - clear sky index (KC) – Albedo- Normal direct irradiation (DNI) Abstract Illuminance is the power of radiation per unit area (W/m2 ). Its projection on the ground on a horizontal plane named GHI (Global horizontal irradiance) is the meteorological quantity commonly used to estimate and forecast photovoltaic production. The GHI at a given location varies mainly according to the zenithal solar angle and the transparency of the atmosphere. The first variable can be calculated with good accuracy, the second depends on the cloud cover and the concentration of optically active atmospheric components. Apart from clouds, solar radiation modeling for solar energy generally retains aerosols, water vapor and ozone as significant components. A few Moroccan researchers have been able to estimate the global horizontal GHI irradiance using ground-based measurements. These data are insufficient because the measurement stations are located in well-defined geographical sites and therefore do not cover all the Moroccan national territory. The scientific literature specifies that images taken by geostationary satellites are a reliable source to obtain solar irradiance data with a quasi continuous spatial coverage. The objective of the present work is to evaluate the GHI for the whole Moroccan national territory from the images of the second generation MSG meteorological satellites by the procedure of the two methods Heliosat-2 and ARSC (Atmospheric Science Research Centre)