Advanced metrology sensor applications for improved pointing performance of the Greenland Telescope

The Greenland Telescope (GLT) currently achieves a blind pointing accuracy of 2" rms, sufficient for 230GHz VLBI operations at Pituffik Space Base. Plans to relocate the antenna to Summit Station are underway to enable observations at ≥690GHz, which requires improving the pointing accuracy due to smaller beam sizes at higher frequencies. Since achieving the ALMA-standard referenced pointing accuracy of less than 1" for single-dish operations is impractical due to limited sensitivity, GLT's strategy involves real-time adjustments using data from metrology sensors, following the Systematic Pointing Error Model (SPEM) by the antenna manufacturer (Vertex Antennentechnik). This paper highlights our metrology system's role in predicting pointing corrections through real-time monitoring of inclinometers, linear, and temperature sensors. Additionally, we introduce a night-viable optical guidescope system for astrometric referencing of star-fields, aiming to enhance pointing precision for high-frequency VLBI with the GLT.