Effect of the alidade thermal behavior on the pointing accuracy of a large radio telescope

Abstract

The alidade’s non-uniform temperature field of a large radio telescope is very obvious under solar radiation. Estimating a radio telescope’s pointing errors, caused by the alidade deformation under solar radiation, is significant to improve the telescope’s pointing accuracy. To study the effect of the alidade thermal behavior on the pointing accuracy of a large radio telescope, a temperature experiment is first carried out in a 70-m radio telescope on a sunny day. According to the measured results, the temperature distribution rule of the alidade is summarized initially. In addition, the alidade’s temperature field is calculated by finite element thermal analysis. The simulated results are proved to be in good agreement with the experimental results. Finally, the alidade deformation under solar radiation is computed by finite element thermal-structure coupling analysis. The telescope’s pointing errors caused by alidade deformation are estimated via the alidade’s node displacements. The final results show that the effect of alidade thermal behavior on the telescope’s elevation pointing errors Δ ε 2 + Δ εr is much more than the effect on the telescope’s cross-elevation pointing errors Δ ε 1. The maximum of Δ ε 2 + Δ εr is more than 45″, while the maximum of Δ ε 1 is less than 6″. This study can provide valuable references for improving the pointing accuracy of large radio telescopes.