KEYWORDS: Reflectors, Radio telescopes, Error analysis, Solar radiation, Thermal deformation, Thermal effects, Solar radiation models, Receivers, Thermal modeling, Analytical research
The thermal behavior of the reflector system under solar radiation has great effects on the pointing accuracy of large radio telescopes. To estimate the dynamic pointing error of large radio telescopes caused by the thermal behavior of the reflector system under solar radiation, the nonuniform temperature field and the thermal deformation of the Wuqing 70 m radio telescope (WRT70) on three specific sunny days are first simulated by finite-element (FE) software. Then the pose variations of the reflector system are calculated equivalently based on the FE thermal-structural coupling analysis of the reflector system. Finally, the dynamic pointing errors of the WRT70 on three specific sunny days, caused by the thermal behavior of the reflector system, are estimated according to the beam deviation factor. The research results show that the rotations of the main reflector and the offsets of the subreflector on sunny days have great influences on the pointing error of large radio telescopes. In addition, the pointing error caused by the rotations of the main reflector and the pointing error caused by the offsets of the subreflector cancel each other out, but the pointing error caused by the rotations of the main reflector plays a dominant role. Furthermore, the effect of the thermal behavior of the reflector system on the pointing accuracy of large radio telescopes is less than the influence of the thermal behavior of the alidade. These findings could provide valuable references for the compensation of dynamic pointing errors of large radio telescopes.
The azimuth rotation part of a large aperture radio telescope usually takes one wheel-rail system; therefore, wheel-rail pointing errors and wheel-rail wear are very important to antenna point accuracy. First, this paper discusses the wheelrail contact theory and some specific characteristics of wheel-rail system in large aperture radio telescope. Second, one 3D model of wheel-rail contact system is built according to the parameters of 50m antenna in China, and the model is analyzed by one whole body in MSC.Patran/Nastran. Third, we use the multi-body dynamic method to build the model of wheel-rail and simulate it in RecurDyn software. Comparing the simulation results, we find that the coupling of rigidbody and soft-body is much more precise than one whole body in describing the contact deformation. And the results also explain the crevice’s influence on the mechanical properties of wheel-rail contact system. Finally, some experiments and measurements of 50m antenna are made, by which we get some useful tips for large aperture radio telescope. The test results show that the multi-body dynamic method is much more suitable to the mechanical analysis in wheel-rail contact system.
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