Research On The Pointing Error Model Of The Oblique Axis Terahertz Antenna

The 5m Dome A Terahertz Explorer(DATE5)is a terahertz telescope to be deployed at Dome A,Antarctica.It features a slant-axis mount which is specially designed for polar environment.Compared with a traditional altazimuth or equatorial mount,a slant-axis mount is more adaptable to extreme site conditions such as Antarctica due to its special rotation mechanics.However,devoted study to the pointing model of slant-axis antenna has not been reported yet.In this paper,we try to establish a high accuracy pointing error model for the slantaxis antenna.First,the coordinate transformation relationship between the slant-axis mount and the traditional altazimuth mount is given.Next,an analytical pointing model for the slant-axis antenna is introduced based on an analogy to the pointing model of the traditional altazimuth antenna.Moreover,a novel antenna pointing measurement method based on photogrammetric techniques is proposed.Using this method,behaviors of the antenna beam pointing can be accurately measured without the aid of astronomical observations,and various contributors to the pointing error can be separated and identified.Experimental studies on a 1.2m slant-axis antenna of Purple Mountain Observatory was conducted.Based on the measurement results,an analytical model consisting of seven terms are established,and some new error terms are added to the traditional model to improve the fitting accuracy.Some of the major contributors to the pointing error are measured individually by photogrammetry and their respective coefficients are compared with those in the overall pointing model.Finally,the analytical model and BP neural network model were combined to yield an optimized model of high accuracy and robustness.