Scientific Investigation of Asteroid Surface Robot Lander "MINERVA" on board HAYABUSA

In recent years, missions for exploring small planetary bodies such as asteroids and comets have received great attentions across the world. In upcoming asteroid or comet missions, It is increasingly important for planetary science to make science-equipped rovers hang around the surface of small planetary bodies whose surface gravity is very small.The Institute of Space and Astronautical Science (ISAS) of Japan launched an engineering test spacecraft, HAYABUSA to a near Earth asteroid 1998SF36 in May 2003. The authors have proposed a small robotic lander for MUSES-C mission. This robot is called "MINERVA" (MIcro/Nano Experimental Robot Vehicle for Asteroid), which has mobility system by hopping. Under the microgravity environment on the surface of small planetary bodies, traditional wheeled rovers are not expected to move effectively due to the low friction and inevitable detachment from the surface. Therefore the authors have proposed a hopping rover for the mobility in the microgravity environment. This rover includes a torquer inside and has no apparent moving parts outside. Turning the rover by rotating the torquer, the reaction force against the surface makes the rover hop with significant horizontal speed, which can overcome the difficulties of mobility around the small bodies. This paper describes the microgravity experiments of the proposed rover which is driven by an DC motor torquer. Experimental results are compared with the computational simulations.