An estimate of the time-varying temperature field of the main reflector and subreflector of the Shanghai 65 m radio telescope under solar illumination

摘要

The time-dependent temperature fields of the reflectors of the Shanghai 65 m radio telescope are investigated numerically, taking account of the non-uniform heating of the reflector surfaces due to solar illumination and the constantly changing ambient air temperature. This paper utilizes a ray casting algorithm to calculate the borderline separating the reflector areas in shadow and in sunshine, aiming to provide an accurate calculation of the solar energy absorbed. Then a ray tracing algorithm is utilized to calculate the total solar energy that is reflected by the main reflector area and received by the subreflector surface area. Finally, the solar energy is used as the main thermal load on the reflector surface to numerically examine the temperature distribution on both the main reflector and the subreflector. The results illustrate that the time-varying temperature fields of the reflectors of a radio telescope due to asymmetric solar illumination can be accurately simulated utilizing the ray casting algorithm and the ray tracing algorithm. The occurring periods and avoidance zones of the overheating of the subreflector are identified, among which the maximum temperature of the subreflector reaches 144.9A degrees C. These dangerous observation zones should be avoided during the operation of the radio telescope.