Vol 20, No 1

Active sub-reflector research for a large radio telescope

Jin-Qing Wang, Rong-Bin Zhao, Yong-Chen Jiang, Zheng-Xiong Sun, Lin-Feng Yu, Li Fu, Qin-Hui Liu, Wei-Min Zheng, Zhi-Qiang Shen


Abstract This paper proposes an active sub-reflector suitable for large radio telescopes, which can compensate both of the deformation of the main reflector and sub-reflector position offsets. The mathematical formula of the main reflector deformation compensated by the sub-reflector is deduced based on Cassegrain and Gregory antenna structures. The position of the sub-reflector is adjustable to compensate for defocusing errors on high and low elevations, which are mainly caused by the deformation of the sub-reflector supporting legs. In this paper, the method of obtaining the optimum position of the sub-reflector from the aperture phase by the interferometric method is introduced. The actual measurement is verified on the Tianma 65 m radio telescope, which provides a new way to diagnose the position error of the sub-reflector.


Keywords radio telescope — deformable sub-reflector — model — holography — phase

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