This paper focuses on the telescope gain affected by a multilevel hybrid mechanism for the feed positioning in the five-hundred-meter aperture spherical radio telescope (FAST) project, which is based on the positioning accuracy analysis of the mechanism. First, error model for the whole mechanism is established and its physical meaning is clearly explained. Then two kinds of error sources are mainly considered: geometric errors and structural deformations. The positioning error over the mechanism's workspace is described by an efficient and intuitive approach. As the feed position error will lower the telescope gain, this influence is analyzed in detail. In the end, it is concluded that the design of the mechanism can meet the requirement of the telescope performance.
1.Chinese Acad Sci, Natl Astron Observ, Joint Lab Radio Astron Technol, Beijing 100012, Peoples R China 2.Chinese Acad Sci, Key Lab Radio Astron, Beijing 100012, Peoples R China
