On-Board Computers for Micro-Satellites

Abstract

Space Robotics Laboratory (SRL) of Tohoku University has been developing micro-satellite technologies and successfully demonstrating micro-satellite and CubeSat technologies in orbit in the past 10 years. The main computers of these satellites are all custom-made computers based on commercial off-the-shelf (COTS) components. SRL specifies on-board computers' specification and develops both software for the processors and the hardware logic for the FPGAs, supported by industrial manufacturing companies. The specification and radiation tolerance levels of these computers vary based on what types of functionalities they are responsible for, such as power control, attitude control, signal processing, etc. Through the experiences of ground development and orbit demonstration, SRL has accumulated design strategy of on-board computers for micro-satellites by utilizing a combination of FPGAs, and CPUs. These also include small scale microcomputers, System-on-Chip softcore-based computers, purely FPGA-based software-free computers, and very complex triple module redundant multi-processor computers. Functionalities of all these computers were evaluated in orbit. This paper will describe the design strategies applied for the past missions at the SRL, system reliability assessments of the designed computer architectures, and discuss about on-board computer design approaches for future micro space systems.