A Peltier cells-based temperature controller for Sun simulators

In the framework of a low-cost educational project aimed at the design, manufacturing, launch and operations in orbit of a student satellite, the microsatellite laboratory of the II Faculty of Engineering of the University of Bologna in Forlì has established a collaboration with the Electronics laboratory in the Department of Aerospace and Astronautical Engineering (DIAA) of the University of Rome “la Sapienza”. This collaboration is focused on the electrical tests of the terrestrial Si solar cells being used for the low-cost manufacturing of the solar panels for the microsatellite. A Sun Simulator, capable of determining the characteristic I-V curve of a solar cell, was already available at DIAA premises. As the Sun Simulator was not capable of actively controlling the temperature of the solar cell under test (only an open-loop system based on six series connected Peltier cells was installed), it was agreed that the microsatellite laboratory of the University of Bologna could contribute to the development of that device, by designing, testing and installing a closed-loop temperature control system. The target temperature control accuracy was in the order of one degree Celsius, a value small enough to render the solar cell characteristic curve nearly independent of the small temperature variation experienced during the electrical test. Making use of the experience gained by the aerospace group of the University of Bologna in the use of microcontrollers for space applications, it was decided to implement the temperature controller using the same microcontroller used on-board the microsatellite under development in Forlì. This paper describes the hardware and software design carried out in the microsatellite laboratory in order to assembly a reliable, yet reconfigurable, device, to be successively installed and tested at DIAA premises in Rome.