Main reflector gravity deformation and sub-reflector position measurement for radio telescope based on interferometer

Abstract

This paper focuses on the measurement of the main reflector gravity deformation and sub-reflector position change on Tianma 65 m (TM65 m) radio telescope. Firstly the paper summarizes the methods of principal measurement. Microwave holography and cross scan pattern are disscussed. Then the gravity deformation of the main reflector over the entire elevation measured by VLBI method is discribed. The measurement accuracy is also estimated. At last, the gravity model is constructed and compared with the simulation. They agree with each other. The formulas along with the simulation give a description between the offsets of feed, sub-reflector and the aperture phase. The sub-reflector position ofTM65 m is obtained by the least square method that applied on the aperutre phase and the formulas. The sub-reflector positions measured are consistent with that of the traditional amplitude method in X , Y and Z directions. This method provides a different way to measure the position model of the sub-reflector.