A position sensing device's application on TianMa radio telescope

Based on the platform of Shanghai TianMa 65m radio telescope, a PSD (Position Sensing Device) has been installed. As we know, for large telescopes, many factors including temperature, gravity deformation and wind load can result in sub reflector's (SR) position moving, which can make telescopes' focus's change and pointing error's increasing. For existing methods, we always choose night with good weather to measure antenna's pointing error and then establish the pointing model. Contrast to the models, the system provided in this paper can identify the SR's two dimensional position offset real-timely. It can measure SR's position intuitively. Also an anemorumbometer has been installed on the SR of TMRT to measure the wind speed and direction at the height of SR.