Motion Planning of Intelligent Explorer for Asteroid Exploration Mission

In-situ observations of minor bodies like asteroids or comets are scientifically very important because their sizes are too small to have high internal pressures and temperatures, which means they should hold the early chemistry of the solar system. In recent years, some rendezvous or sample-return missions to small body have received a lot of attention in the world. To date, the missions of NEAR (Farquhar, 2001), Deep Space 1 (Rayman et al., 2000), Deep Impact (Chiu et al., 2000), and Stardust (Atkins, et al., 2000) have been successfully performed, while MUSES-C (Kawaguchi et al., 2000) and Rosetta (Wittmann, et al. 1999) are currently in operation. NEAR spacecraft was successfully put into the orbit of the asteroid 433 Eros in February 2000. After precise remote-sensing observations, NEAR spacecraft succeeded in hard-landing on the surface of EROS in February 2001. In Japan, meanwhile, ISAS (Institute of Space and Astronautical Science) launched an asteroid sample and return spacecraft MUSES-C toward a near Earth asteroid 1998SF36 in 2003 and performed soft landing on the asteroid in 2005. In deep space missions, ground based operation is very limited due to the communication delay and low bit-rate communication. Therefore, autonomy is required for deep space exploration. On the other hand, because little information on the target asteroid is known in advance, robotics technology is used for the spacecraft to approach, rendezvous with, and land on the asteroid safely. Various kinds of advanced and intelligent robotics technologies (Kubota et al. 2001) have been developed and used for navigation and guidance of the explorer to touch down and collect samples. This chapter describes the outline of the sample return mission MUSES-C, descent and touch-down scenario, vision based navigation scheme, sensor based motion planning, autonomous functions, and flight results in detail. This chapter is structured as follows. Section 2 describes the mission purpose and the configuration of MUSES-C spacecraft. In Section 3, navigation sensors are explained. In Section 4 discusses the strategy for autonomous approach and landing. Autonomous descent scheme based on navigation sensors is introduced. In Section 5, a vision based navigation scheme is presented. In Section 6, flight results in MUSES-C mission is presented. Finally, Section 7 is for discussions and conclusions.