The objective pursued with this Final Bachelor thesis is to support the activity of Remote Sensing research group of the UPC, which are developing the Cubesat UPCSat-1, a picosatellite with 10x10x10cm dimension (1U). This project aim's is purely educational and the acquired knowledge may be used for building and improving next picosatellites. The support activity mentioned consists in characterize a solar simulator which is necessary for the Cubesat's certification tests. In addition, it will verify the proper performance of the solar cells installed in the Cubesat's faces. In this characterization process the proper material will be used (pyranometer, spectrophotomer, the corresponding software...) to determine the intensity distribution of the beam, the spectrum produced by the simulator and the stability that this beam provides. After this characterization, a thermal simulation with Thermal Desktop will be done. We will put the Cubesat inside the vacuum chamber and the solar simulator will be radiating the picosatellite. When the simulation is ended, we are going to proceed to verify the results experimentally.