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Study on the pointing model of a slant-axis terahertz antenna

This paper describes the establishment and verification of an accurate pointing model for a 1.2 m aperture slant-axis terahertz antenna. A new analytical pointing model for the slant-axis antenna is presented based on an analogy to that of the alt-azimuth antennas. Furthermore, extra error terms are added to the pointing model based on the structure and mechanical analysis of the slant-axis antenna. To verify the pointing model experimentally, a pointing error measurement method based on photogrammetric techniques is proposed. Using this method, pointing behaviors of the antenna are accurately measured without the aid of astronomical observations, and major sources of the pointing errors are measured individually by photogrammetry and their respective coefficients are compared with those in the analytical pointing model. The results show that an extended pointing model consisting 21 error terms can significantly reduce the residual systematic errors compared with the traditional model, more details are given in the following sections.