Effect of the alidade thermal behavior on the pointing accuracy of a large radio telescope

Abstract

The alidade’s non-uniform temperature field of a large radio telescope is very obvious under solar radiation. Estimating a radio telescope’s pointing errors, caused by the alidade deformation under solar radiation, is significant to improve the telescope’s pointing accuracy. To study the effect of the alidade thermal behavior on the pointing accuracy of a large radio telescope, a temperature experiment is first carried out in a 70-m radio telescope on a sunny day. According to the measured results, the temperature distribution rule of the alidade is summarized initially. In addition, the alidade’s temperature field is calculated by finite element thermal analysis. The simulated results are proved to be in good agreement with the experimental results. Finally, the alidade deformation under solar radiation is computed by finite element thermal-structure coupling analysis. The telescope’s pointing errors caused by alidade deformation are estimated via the alidade’s node displacements. The final results show that the effect of alidade thermal behavior on the telescope’s elevation pointing errors Δ ε 2 + Δ εr is much more than the effect on the telescope’s cross-elevation pointing errors Δ ε 1. The maximum of Δ ε 2 + Δ εr is more than 45″, while the maximum of Δ ε 1 is less than 6″. This study can provide valuable references for improving the pointing accuracy of large radio telescopes.

Effect of the reflector system thermal behavior on the pointing accuracy of large radio telescopes

“…The maximum of the elevation pointing errors, caused by the thermal behavior, of the reflector system of WRT70 is 16.8 arc sec, whereas the elevation pointing errors, caused by the thermal behavior, of the alidade of WRT70 is up to 45 arc sec according to our previous research. 17 This study confirms that the influence of solar radiation on the pointing accuracy of large radio telescopes cannot be ignored. It provides a valuable reference for evaluating the dynamic pointing accuracy of large radio telescopes.…”

“…16 The alidade's thermal behavior of the WRT70 under solar radiation was discussed in 2021. 17 The influence of the thermal behavior of the reflector system on the pointing accuracy of large radio telescopes should never be ignored. To estimate the pointing error of large radio telescopes caused by the thermal behavior of the reflector system, the FE analysis and relevant calculations on the WRT70 are performed in this paper.…”

Estimation of Pointing Errors of Large Radio Telescopes under Solar Radiation Based on Digital Twin

“…Over the past decades, the thermal behaviors of many foreign radio telescopes have been studied overseas via combining finite-element (FE) calculations and relative experiments, including the thermal deformation of the reflector system of the RT-70 radio telescope [9], the thermal design of the quadripod and backup structure of the IRAM 30-m telescope [10], and the thermal analysis of the alidade of the Medicina 32-m telescope and the Sardinia 64-m telescope [11][12][13]. In recent years, the thermal behaviors of several domestic radio telescopes also have been researched in China based on FE analysis and experimental measurements, such as the thermal effects of the alidade of the Nanshan 25-m radio telescope and the Miyun 50-m radio telescope [14,15], the nonuniform temperature and the thermal behavior of the Tianma 65-m radio telescope [16,17], the thermal deformations of the alidade and the reflector system of WRT70 [18,19]. To sum up, extensive studies on the thermal behaviors of radio telescopes have been done, but the research on estimating the total pointing error caused by the thermal behaviors of large radio telescopes is poor.…”

Measurement and Correction of Pointing Error Caused by Radio Telescope Alidade Deformation based on Biaxial Inclination Sensor

“…Some commercial inclinometers can reach a resolution of 0.001 mrad, or 0.2 arcseconds [15]. The ability of an inclinometer to measure small inclinations From the perspective of antenna components, a major source of pointing errors is the antenna alidade [2][3][4]. The alidade is the foundation of the antenna, an important part of the antenna azimuth and elevation motion mechanism since it plays a significant role in ensuring perfect orthogonality between the azimuth axis and the elevation axis of the antenna.…”