Batch Measurement and Calibration Method of DSRT Three-axis Low Frequency Antenna Pointing Error

Abstract

Daocheng Solar Radio Telescope (DSRT) is an important part of the solar interplanetary exploration subsystem of the Chinese Meridian Project-Phase II. It operates in the 150$-$450 MHz frequency band, providing high-time, high-angular resolution images of the solar radio burst. Aiming at the high precision pointing measurement of the DSRT antenna and the requirement of batch calibration of pointing errors, the antenna's 3-parameter encoder zero-point offset pointing error model is established by quaternion rotation transformation method according to the unique 3-axis mount system of the DSRT. Then, the drift scanning method based on radio source is proposed to obtain the radiation power pattern of the 16 antennas, and the pointing errors are accurately measured by determining the boresight according to the 2-dimensional power pattern. Finally, the least square method is used to fit the model parameters, and the encoder zero point is readjusted for each axis via antenna control software. Verification of the adjustment results confirmed the reliability and effectiveness of the pointing calibration method. After correction, the pointing accuracy of 16 antennas is within 0.5${}^{\circ }$, which is significantly better than the pointing error of 3.5${}^{\circ }$ before calibration, meeting the requirement that errors are less than 1/10 of the HBPW (half power beam width) at the highest operating frequency of the DSRT antenna.