Contributing to the SpaceWire international standard

−146− Synthesiology English edition Vol.11 No.3 pp.146–157 (Feb. 2017) The X-ray ast ronomy satellite “ASTRO-H (Hitomi)” dramatically improved functions and performances required for satellite systems compared with conventional Japanese satellites. Development of equipment onboard ASTRO-H was conducted under wide-ranging international cooperation. Therefore, development that ensured continuation of the conventional development as well as compliance to international standard was required. The SpaceWire international standard employed for ASTRO-H was a de jure standard that the European Space Agency (ESA) oversaw. We were able to incorporate proprietary standards that were formed with Japanese scientific satellites over the years into the international standard.