The X-Ray Imaging and Spectroscopy Mission (XRISM) is the successor to the 2016 Hitomi mission that ended prematurely. Like Hitomi, the primary science goals are to examine astrophysical problems with precise highresolution X-ray spectroscopy. XRISM promises to discover new horizons in X-ray astronomy. XRISM carries a 6 x 6 pixelized X-ray micro-calorimeter on the focal plane of an X-ray mirror assembly and a co-aligned X-ray CCD camera that covers the same energy band over a large field of view. XRISM utilizes Hitomi heritage, but all designs were reviewed. The attitude and orbit control system were improved in hardware and software. The number of star sensors were increased from two to three to improve coverage and robustness in onboard attitude determination and to obtain a wider field of view sun sensor. The fault detection, isolation, and reconfiguration (FDIR) system was carefully examined and reconfigured. Together with a planned increase of ground support stations, the survivability of the spacecraft is significantly improved.

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A three-axis attitude control function module was assembled into a highly integrated cubic package (10 3 cm 3 dimension: 1U-sized). The key feature of the cubic module is its high-agility functionality, which is realized by a novel, compact electromagnetic braking mechanism combined with a ferromagnetic wheel. In this study, the proposed concept is compared with existing 1-axis wheel assemblies and the conventional CMG scheme in terms of momentum storage per mass/volume, maneuvering speed, and compactness. A prototype of the module was manufactured to demonstrate this innovative concept.

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