Vol.11 no.3 2019

Commentary : Contributing to the SpaceWire international standard (H. HIHARA et al.)−147−Synthesiology - English edition Vol.11 No.3 (2018) and proposals to be reected in the international standard in the development process of ASTRO-H. Moreover, in looking back at the Japanese behavior pattern up to the moment the proprietary technologies and proposals were incorporated in the international standard, in Chapter 4, we compare this behavior with those of the American and European personnel referring to the model described in Reference [8] and consider the reproducible proposal process utilizing the Japanese behavior pattern.2 System architecture of ASTRO-HThe development of ASTRO-H was conducted under international collaboration to realize an “open platform” described in Reference [10], as a situation Japan aims to realize in the future. This is a condition in which new ideas, technology, and people gather from around the world, and state-of-the-art added values are generated at a Japanese center of activity. It aims to make Japan the center for global intellectual activity. It also aims to create a structure to solve the problems that prevent the development of a spacecraft system that may produce innovative results, through cooperation transcending organizations. By lowering the threshold of joining the development of spacecraft systems, it provides opportunities for participation by a wide range of citizens.As equipment installed in scientic satellites become diverse, the major issue is the difculty of conducting development in a short time period while maintaining high reliability, as well as the complexity of the tests during the developmental process. Therefore, the R&D for spacecraft system architecture has advanced to conduct highly reliable design from the perspective of data handling and intercommunication among onboard equipment.[11][12] Scientific satellites involve a wide variety of mission purposes, such as near-earth or deep space observations. Since different forms have to be adopted, depending on their missions, one of the most important perspectives is to make a data handling system scalable for the architecture that can be used commonly in small and large satellites, rather than the concept of a xed common bus. The network of electronic equipment installed onboard ASTRO-H that complies with the SpaceWire international standard was developed based on the “Future prospect of data handling system of scientific satellites” described in Reference [13]. The fully redundantNote 1) SpaceWire network that aimed for the SpaceWire international standard was realized for the rst time in the world in ASTRO-H.[14] It was highly acclaimed in Europe where the standard was established, and ASTRO-H was introduced in the opening pages of the material published by ESA for the public, as shown in Fig. 1.[15]3 Efforts by JapanIn developing the satellite onboard communication standard for ASTRO-H, approach was taken in which the personnel of Japan actively contacted the personnel of Europe and USA, conducted practical development and onboard demonstration from the planning stage of the standard. The team proposed improvement to the specications that were derived through abundant achievement in Japan for the international standard. For the test and validation environment of the equipment that complied to the SpaceWire international standard, international joint R&D was done from the planning stage, and R&D and preparations were conducted to aim at unifying international understanding for handling the off-nominalNote 2) conditions that were not written in the specications.[16]It was the first time that a proposal from Japan was incorporated into the international standard for satellite onboard networks. The proposal from Japan was of a wide variety, from definitions of major protocol layers to fine correction of errors. In this chapter, we look back over the major three points that were incorporated into the standard, as well as the international joint R&D of the test and validation environment. These are culmination of Fig. 1 SpaceWire international standard and ASTRO-H were presented in WELL CONNECTED, European Space Agency Bulletin (February 2011)[15]

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