A High-Pointing-Accuracy Implementation Method for an 18-m Antenna Based on a Multi-Error-Source Coupled Model

Abstract

Highlights What are the main findings? A multi-error-source coupled model is established, unifying geometric, gravity, wind, and dynamic errors, and revealing their coupling mechanisms (geometric-physical, control-structure, and error-synthesis coupling). Using RMS@95% and RSS synthesis, the total pointing error of the 18-m antenna is budgeted at 9.9 arcseconds (at 40 GHz), with wind-induced deformation (7.60 arcseconds) identified as the dominant error source. A three-level hierarchical compensation strategy is proposed—mechanical adjustment, TPOINT parametric calibration, and active servo suppression—with explicit mapping between physical error sources and TPOINT model parameters (e.g., IA, IE, NPAE, AN, CA, CE, GCE). What are the implications of the main findings? The achieved 9.9-arcsecond accuracy meets the stringent ≤ 1/10 half-power beamwidth requirement for 40 GHz VLBI observations, enabling high-frequency interferometry with minimal signal attenuation and phase distortion. The transparent error-source–to-parameter mapping transforms calibration from black-box fitting to physical diagnostics, improving debugging efficiency and providing a systematic engineering framework for precision design and implementation of large high-frequency antennas. The clear identification of wind load as the primary error source highlights the need for enhanced environmental disturbance mitigation, and the hierarchical structure offers a modular pathway for future adaptive compensation under harsher conditions (higher winds or faster scanning). Abstract High-frequency VLBI (Very Long Baseline Interferometry) observations impose stringent requirements on antenna pointing accuracy. This paper proposes a high-precision pointing implementation method that integrates a multi-error-source coupled model with hierarchical compensation. Taking an 18-m antenna as the object of study, the influence of gravity is quantified through structural-electromagnetic coupled simulation, establishing a unified model encompassing geometric, random, environmental, and dynamic errors. Using the 95% confidence bound (defined as 1.96σ for each error component) and the RSS (Root Sum of Squares) synthesis method, the budgeted system pointing error is estimated to be 8.64 arcseconds (at 40 GHz). An innovative three-level compensation system of “mechanical adjustment—model calibration—active suppression” is constructed, clarifying the mapping relationship between error sources and the TPOINT (Telescope POINT) model. To validate the proposed approach, actual radio source tracking experiments were conducted on the 18-m antenna. The experimental results demonstrate that after applying the three-level compensation strategy, the residual pointing error is reduced to approximately 7.9″ (RMS@95%), which agrees well with the theoretical budget of 8.64″. This method provides a systematic solution for the precision design and engineering implementation of high-frequency antennas, with the effectiveness confirmed through both theoretical budgeting and experimental validation.