An Improved Radio Pointing Model for SHARC II of the Caltech Submillimeter Observatory Telescope

In this research, we develop a new method of upgrading the radio pointing model of an important instrument of the Caltech Submillimeter Observatory (CSO) telescope, i.e., the Submillimeter High Angular Resolution Camera II (SHARC II), by making three types of structural reconstruction of its existing model. First, the axial displacement of the secondary reflector of the telescope is introduced to the radio pointing model for SHARC II. Second, the multi-layer perceptron is applied for better describing higher-order terms in the radio pointing model, which are hard to be mathematically formulated. Third, a receding horizon modeling method is proposed to replace the time-dependent term in the existing model, for better reducing the negative impact of the time drift on the model's accuracy. Results of numerical experiments and statistical significance analysis based on the real pointing data of SHARC II show that the reconstructed radio pointing model can improve the accuracy of estimating the pointing error, and the proposed method of upgrading the radio pointing model is effective. Considering that the CSO telescope will be moved from the old site at Maunakea, Hawaii to the new site at the Chajnantor Plateau in Chile, the proposed methods of upgrading the radio pointing model are expected to be employed for pointing correction after the telescope is refurbished at the new site.