The Giant Steerable Science Mirror prototype is being developed to assess the Vacuum Filter Frame tertiary mirror system of the Thirty Meter Telescope.In this study, a new semi-kinematic coupling design is proposed for the prototype based on three pairs of V-grooves and canoe-like components to allow for high repeatability accuracy under heavy loads.A mathematical model was constructed to estimate the repeatability accuracy using the corresponding measurement results and machining errors.The proposed design was verified by an experiment, and the results were consistent with the mathematical model.
Furthermore, the results indicate that the repeatability PLAYTIME of the semi-kinematic coupling is sufficient for the requirement.