We have begun the feasibility study to build a small satellite in the 3kg mass range and in the power range less than 30W since October in 1998, sponsored by National Space Development Agency of Japan (NASDA). This satellite installs three reaction wheels for an attitude control and camera which will demonstrate optical navigation experiment by using image processing. The BBM design status is described in this paper. The components such as a small reaction wheel, electric flash and onboard computer were built. Mothership - daughtership technology and formation flying experiments are planned. New electric propulsion is being developed for small satellite