Green Bank Radio Telescope: Wind Induced Effects on Feed-Arm

Abstract

Radio Telescopes have been widely used in deep-space exploration and satellite communications. High pointing accuracy is required to be high in these applications, since the beams involved in these measurements are narrow. However, pointing precision can be influenced by wind load effects, which represent a disturbance source for the support structures of the telescope, especially in the high-frequency range. This paper analyzes the wind load effects on the feed arm of the Green Bank Radio Telescope (GBO) for two different wind directions as a function of the wind speed. A Finite Element (FE) Model of the GBO has been assembled to evaluate the dynamic response of the structure against turbulent wind disturbances. The FE model has been updated according to results derived from previously developed models. The paper focuses the attention on the wind induced displacements of the feed arm, which is, for the examined structure, the main source of wind disturbances. The study shows that wind disturbances can deeply affect the pointing accuracy of GBO even at low wind speeds. Namely, for reference mean wind speed of 4 m/s the total along-wind lateral displacements of the feed arm can reach the maximum threshold associated with an acceptable Pointing Error (PE). Furthermore, dis-placements are larger for winds acting in the cross-elevation direction and can deeply affect pointing accuracy of the antenna measurements.