Sub-reflector model depending on elevations and performance evaluation for TM65 m radio telescope

A sub-reflector system of the TianMa 65 m radio telescopes has been installed in order to compensate for the gravitational deformation of the sub-reflector support and the main reflector. The position and attitude of the sub-reflector are variable in order to improve the pointing performance and the efficiency at different elevations. A model has been constructed to determine the position and attitude of the sub-reflector with elevation. Test results show that the sub-reflector model can effectively improve the efficiency of the 65 m radio telescope at both high and low elevations, where the efficiency can be improved by 20% and 15%, respectively. At X band, the aperture efficiency of the radio telescope reaches more than 60% over the entire elevation range. Pointing deviations caused by the sub-reflector model are consistent with the grasp simulation results.