The Meteosat Third Generation programme is an ESA–EUMETSAT partnership to continue and enhance geostationary weather observations for forecasting and nowcasting. Its planned full system combines four imaging satellites and two sounding satellites, with supporting ground infrastructure, rather than six identical spacecraft. The imaging and sounding roles provide complementary views of weather and the atmosphere. The programme is designed to sustain this observing service across successive spacecraft over roughly two decades, distinguishing the long-term system from any single MTG launch.