Recent years have seen a growing interest in space missions involving small satellites. This attraction is due to their relative ease of production, low cost and short development time, making them accessible to a wide range of organizations, including universities, research institutes and commercial entities. Ensuring the reliability of these systems is becoming increasingly important, with thermal analysis and thermal design in particular playing a crucial role in all phases of project development to keep each satellite component within temperature limits to ensure proper operation. This thesis aims to develop a tool implemented in the MatLAB® environment, known as the Small Satellites Thermal Tool (S2T2), created by the Department of Mechanical and Aerospace Engineering at the Politecnico di Torino.