This work discusses the integration of the subsystems in a CubeSat satellite and the implementation of a central "On-Board Controller & Data Handling" system. Potential radiation problems are investigated and addressed. CubeSTAR is a CubeSat satellite developed at the University of Oslo. The satellite requires some method of handling commands and sending data to the ground station. The satellite needs to be autonomous, so a method of coordinating the operation of each subsystem is required. The On-Board Controller integrates all the satellites subsystems to a unified control- and monitoring...