The Sirio satellite was launched from Cape Canaveral on August 25, 1977. The project originated from an idea of Prof. Francesco Carassa, who aimed at building a satellite reaching 18GHz transmission frequency for space telecommunications, a technology not available in Europe at that time. Carassa was the scientific supervisor of the project. He led a relevant part of the research, which took place in the experimental station at Spino d’Adda, 30 km south-east of Milan and in other larger stations situated in Gera Lario and Fucino. These stations hosted the main terminals for the satellite control and the reception of the full set of propagation signals. Many international research centers participated in the experiment both in Europe and in the United States and, later on, in the Popular Republic of China. The scientific activities, which lasted until 1984, were coordinated by researchers of the Politecnico di Milano, where all the data collected in Italy were concentrated and analysed in the framework of the activities of the Center for Studies in Spatial Telecommunications chaired by Prof. Francesco Carassa and directed by Prof. Guido Tartara.