The success of a satellite mission depends on a lot of factors. The satellite thermal control system (TCS) is one of the most important subsystems that ensures that the satellite’s components remain within an acceptable temperature range. Thermal control for satellites includes monitoring the energy that flows into and out of the spacecraft. This monitoring helps to prevent overheating or freezing of critical components. To execute satellite thermal modeling, the mathematical model must be solved while accounting for both the heat rejected out of the internal electrical components of the satellite subsystems and the effect of the different forms of external fluxes. This paper focuses on changing the design of a 3U CubeSat by adding a deployment mechanism. And using passive and active thermal control components guarantees that the satellite stays within the temperature range that allows for satellite operation. At an altitude of 421 km, the spacecraft is in the Low Earth Orbit. SINDA FLUINT and Thermal Desktop Software were used to analyze the satellite thermal data to make sure that the temperatures of the satellite’s electrical equipment are kept within ranges that are suitable for regular operation. The process was validated, and the results were checked by performing hand calculations and computer simulation to improve our thermal analysis’s reliability. The results of the modified design have achieved a better temperature range and better solar panel exposure area to the sun. It is imperative to underline that this work is integral to building a 3U Cube Satellite as a graduation project.