# Air Subdivision Research of Laser Atmospheric Propagation Between Dual Reflectors of the Large-Aperture Antenna

## TL;DR

This paper improves laser-based antenna attitude measurements by modeling temperature gradients between dual reflectors in large-aperture antennas.

## Contribution

Proposes a new air stratification theory and CFD model to better predict temperature gradients in dual-reflector antennas.

## Key findings

- A new air stratification theory improves temperature gradient modeling in dual-reflector antennas.
- CFD simulations accurately model atmospheric stratification under varying antenna positions.
- Experimental validation confirms the theory's effectiveness in improving measurement accuracy.

## Abstract

Laser measurement technology is widely used for deformation or pose monitoring of the dual-reflector antenna systems. However, conventional models of surface temperature variation with altitude fail to accurately characterise the temperature gradients between the main reflector and the subreflector of the large-aperture antennas, due to the complex near-ground environment, the antenna’s dual-reflector structural properties, and the antenna’s own rotation changes. This temperature modelling discrepancy significantly influences the laser atmospheric propagation deflection characteristics, ultimately leading to a decrease in the accuracy of antenna attitude measurements. To address these issues, this paper proposes a theory of air stratification within large-aperture antennas and utilizes this theory to optimize the temperature gradient between the antenna’s dual reflectors. Secondly, a coupled heat-fluid dynamics model for the dual-reflector surfaces is established using Computational Fluid Dynamics to simulate the atmospheric stratification under different rotational positions of the antenna. Finally, the effectiveness and feasibility of the proposed theory were verified through experiments in the antenna model and the China Nanshan 25 m non-rotatable antenna. This research provides an original theoretical and practical basis for precision environmental modelling in antenna measurements, offering prior assurance for improving the accuracy of laser-based antenna attitude measurement.