Study On The Pointing Error Model Of Terahertz Telescopes With Optically Assisted Pointing Measurements

In view of the scarcity of terahertz astronomical point source targets and the difficulty of pointing measurement,this paper studies the method of using a small optical telescope coaxial with terahertz antenna to assist the pointing measurement of terahertz telescope and establish the pointing error correction model.Based on the 1.2m oblique axis terahertz antenna of Purple Mountain Observatory and a 100 mm aperture refracting optical telescope mounted on the antenna back frame,the experiment of optical aided pointing measurement was carried out.Firstly,we derive the pointing error model of oblique axis telescope by analogy.In addition,by analyzing the structure of the slant axis antenna and the error sources of atmospheric refraction and local star time deviation,a slant axis optical pointing correction model with 23 error terms is established.Next,the method of optical aided pointing measurement is introduced.The azimuth and elevation angle in the horizon coordinate system are obtained by using the CCD to take the fits image of celestial body.According to the experimental results,the accuracy of repeated difference is measured and the model fitting error is corrected.The photoelectric axis consistency is calibrated with the help of high-precision digital photogrammetry,and the influence on the accuracy of pointing model is discussed.Finally,BP neural network model is used to train the fitting residuals,which further improves the accuracy of the whole optical pointing correction model.The research results of this paper will provide technical reference for the 5m Dome A Terahertz Explorer(date5)and other terahertz telescopes in pointing measurement and pointing correction model.