Quick analysis of radiation pattern for Leighton Chajnantor Telescope under wind load

Abstract

Leighton Chajnantor Telescope (LCT) will be moved from the summit of Mauna Kea, Hawaii to Chajnantor Plateau, Chile. At the new site, strong wind load will cause structural deformation of LCT's reflector antenna and hence influence its electromagnetic (EM) performance significantly. Radiation pattern is an important indicator of the EM for a reflector antenna and will also be greatly affected by structural deformation. For accurately and rapidly compensating for the affected EM of LCT's reflector antenna, it is essential to develop a quick calculation method for radiation pattern analysis under varying wind loads based on our previous work on the effect of gravitational load on radiation pattern. In this paper, we propose an approximate calculation method for the optical path difference (OPD) due to the deformation of LCT's reflector antenna under wind load. Then a mathematical formulation based on modified Zernike polynomials is presented to fit the calculated OPD. Finally, the radiation pattern will be obtained by the aperture field integration method. Numerical experiments demonstrate the effectiveness of the proposed quick calculation method for analyzing the radiation pattern of LCT's reflector antenna at its highest working frequency. In comparison with the numerical simulation by physical optics (PO) and physical theory of diffraction (PTD), the proposed quick calculation method exhibits high accuracy for the performance criteria of the radiation pattern and reduces the time consumption for radiation pattern analysis significantly.