The position and attitude of sub-reflector modeling for TM65m radio telescope

In the course of astronomical observations, with changes in angle of pitch, the large radio telescope will have different degrees of deformation in sub-reflector support, back frame, main reflector etc, which will lead to the dramatic decline of antenna efficiency on both high and low elevation. A sub-reflector system of the Tian Ma 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. This paper, at the X-band, researched that the changes of position and attitude of the sub-reflector had influence on the efficiency of antenna. Two kinds of model have been constructed to determine the position and attitude of the sub-reflector with elevation, the errors of fitting at the direction of X-axis and Z-axis of two models agreed well, however the large difference at Y-axis. In addition, antenna efficiency were tested with sub-reflector position adjusted and fixed. The results show that the models of sub-reflector can effectively improve the efficiency of the 65m telescope on each pitch angle.