This thesis focuses on the thermal modeling of the Langmuir instrument developed by the Royal Institute of Technology for the Research and Observation in Medium Earth Orbit (ROMEO) satellite. The ROMEO satellite is part of the University of Stuttgart’s small satellite program, developed to test cost-efficient space technologies in LowEarth Orbit (LEO) and MediumEarthOrbit (MEO). Thedeployable Langmuir probesmeasurethethermalplasmaenvironmentanditsinteractionwiththesatellite’s water propulsion system. Using the well-established tool for spacecraft thermal analysis, Systema-Thermica, the project aims to study the thermal behaviour of the instrument, ensuring optimal performance during its lifetime in the harsh conditions of space. To achieve this, a simplified model of the ROMEO satellite, derived from the complete version provided by the University of Stuttgart, was developed.