Application of Infrared Thermal Imager to measure the temperature of Back-Up Structure of the TianMa radio telescope

Two infrared thermal imagers have been installed on the TianMa radio telescope (TMRT) to continuously monitor the temperature distributions of the back-up structure (BUS). In order to compensate the measurement error of the infrared thermal imager (ITI) for a BUS, a correction formula, as a function of measuring distance and viewing angle, is proposed. According to the relationship between the locations of the measurement points in the thermographic image and those in the actual structure, the 3D coordinates of the measurement points are determined by a finite element model of the BUS. Then, the measuring distances and viewing angles are calculated using 3D coordinates of the measurement points. The measurement accuracy of the ITI improves from ±2\(^{\circ }\)C to ±0.5\(^{\circ }\)C with the proposed formula. Additionally, based on the information of rotation angle and rotation speed of the elevation, the problem of the ITI moving with the elevation of the telescope in real time is solved. The temperature data at each elevation are recorded in excel documents respectively which are integrated into a document in chronological order through compiling program. Finally, the temperature of the measurement points at different altazimuthal positions is displayed as curves or contours. The thermal states of about 40% measuring points of the BUS are simultaneously monitored by the ITI, which provides accurate temperature distribution for the prediction of thermal deformations of the BUS.