A Japanese microsatellite bus system for international scientific missions

Professor Shinichi Nakasuka of University of Tokyo is now leading a small satellite development activity within the scope of a Japanese FIRST (Funding Program for World-Leading Innovative R&D on Science and Technology) program. In this program several 50-kg class micro-satellites are going to be developed and launched by the end of Japanese fiscal year of 2013, including one scientific micro-satellite under international cooperation. This program as whole shall contribute to enhance the activities of world's small satellite research societies and industries, and to build the basis of new paradigm for the future, where cost-effective and reliable small satellites are widely utilized for both research and business purposes. Tohoku University has been assigned as the project leader of the above mentioned international scientific micro-satellite, named as RISESAT (Rapid International Scientific Experiment Satellite), and is developing the bus system as well as organizing scientific payload instruments from all over the world together with Hokkaido University and Kyoto University. This satellite shall demonstrate the performance of its bus system which is supposed to be offered as a common bus system for international scientific missions in the future. The selection of scientific instruments is almost finished. The orbit of me RISESAT is planned to be a sun-synchronous orbit with an altitude of between 500km and 800km. In order to accommodate as many payload instruments as possible, the satellite is equipped with two deployable side solar panels enabling a maximum power consumption of up to about 100 W. Many of the attitude determination and control components are going to be developed by the Space Robotics Laboratory of the Tohoku University achieving an attitude control accuracy of better than 0.1 deg. It is also equipped with an X-band transmitter for mission data downlink. The electrical interface between the payload instruments and the bus system is based on a space plug and play avionics standard. The development of engineering model of the RISESAT will be completed by March 2012. This paper summarizes the system design of the satellite and progress report of the development activities, as well as the brief description of selected scientific instruments.