Analysis of Reflector Vibration-Induced Pointing Errors for Large Antennas Subject to Wind Disturbance: Evaluating the pointing error caused by reflector deformation.

Large reflector antennas have been widely used in satellite communications, deep-space exploration, and so on. The pointing accuracy in these applications is required to be quite high as the beams involved are narrow. The pointing accuracy, however, may be influenced by wind disturbance, especially in those with a low natural frequency and constructed without a radome. Furthermore, it is difficult to compensate for such errors without predicting the pointing error (PE) that occurs as a result of reflector deformation caused by wind disturbance. This article analyzes the impact on pointing accuracy of the flexible oscillation of the reflective surface resulting from a stochastic wind disturbance. First, structural deformations are derived from the dynamic equations based on modal analysis. The PEs due to the structural deformations are then analyzed and an analytical model for predicting antenna PE is derived. Finally, a series of simulations based on a 7.3-m Ka-band antenna is undertaken. It verifies the finite-element model used with the help of a modal analysis experiment. The results show that the maximum PE caused by the flexible oscillation of the reflective surface subjected to a wind with a speed of 10 m/s is 0.00527?. In comparison, the maximum PE that can be measured by a shaft encoder is just 0.00768?. In addition, for larger antennas, e.g., 110 m, the total PE (TPE) is revealed to depend mainly on reflector deformation caused by wind disturbance. Thus, it is important to dampen flexible oscillations of large antennas subject to wind disturbances to improve their pointing accuracy.