We have been developing a microsatellite based on our concept of a satellite to meet the potential needs of challenging space-science missions that only a microsatellite can accomplish. A binary black hole (BBH) is a state in which two black holes at the center of their respective galaxies are closing the orbital distance around each other. Observations using conventional large satellites have obtained insufficient results for BBH exploration because the satellites cannot be engaged in the long-term and concentrated observation of astral body such as BBH which is not established the existence. Microsatellites have two advantages; namely, they can be occupied with long-term observation, and they have a low-cost and short-term development compared with large satellites. Thus, we can possibly program a challenging mission for a microsatellite, even with a certain risk. We implemented two key technologies on our microsatellite named ORbiting Binary black-hole Investigation Satellite (ORBIS), namely, a Distributed Architecture with a Common Signboard System and mission-equipment space for astronomical observation equipment. The specifications and progress of each subsystem are reported in this paper, along with an outline and the current status of the ORBIS development.

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