How a primary reflector’s actuators regulate the radiation pattern of a 10.4m submillimeter telescope: Applying the superposition principle

¹ School of Automation, Southeast University, 210096 Nanjing, Jiangsu, China
² State Key Laboratory of Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, China
³ School of Mathematics and Science, Shanghai Normal University, Shanghai 200234, China
⁴ CAS Nanjing Nairc Optical Instruments Co., Ltd., Nanjing, Jiangsu 210042, China

^★ Corresponding authors: This email address is being protected from spambots. You need JavaScript enabled to view it. ; This email address is being protected from spambots. You need JavaScript enabled to view it.

Received: 15 May 2025
Accepted: 27 October 2025

Abstract

Context. The radiation pattern of a radio telescope antenna, particularly in terms of the pointing deviation (PD) and peak gain loss (PGL), is critical for determining the telescope’s front-end sensitivity and angular resolution. These performance indices are highly susceptible to deformations of the primary reflector induced by external loads such as gravity and wind. Active optics, which involves adjusting actuators mounted on the backup structure of the primary reflector, offers a promising solution. However, the underlying mechanism linking actuator adjustment to variations in the radiation pattern is not well understood.

Aims. This research aims to uncover the relationship between actuator adjustment and key performance indicators of a radiation pattern (i.e., PD and PGL) by establishing a reliable analytical framework that enables the precise optimization of the antenna’s electromagnetic characteristics.

Methods. We investigated the radiation pattern of the 10.4 m Leighton Chajnantor Telescope (LCT) antenna under various actuator configurations using the aperture integration method for segmented reflectors (AIMSR). Based on the simulation results, we propose a superposition principle (SP) that approximates the cumulative effect of multi-actuator adjustment as the linear combination of their individual contributions. The mathematical model we developed on the basis of this principle is aimed at describing the functional relationship between actuator displacements and the resulting PD and PGL.

Results. Numerical experiments confirm the accuracy of the SP in capturing the effects of actuator-induced deformation on the radiation pattern. Furthermore, the SP-based mathematical model is validated by its successful application in optimizing actuator configurations to minimize the PD and PGL of LCT’s antenna, thereby enhancing the radiation performance under external loads.

Conclusions. Our findings demonstrate that the proposed SP method provides a physically interpretable and computationally efficient approach to model and optimize the active control of large segmented reflectors. This approach lays the groundwork for high-precision pointing correction for future submillimeter radio telescopes.