Search

In this paper, the wavefront perturbation method based on power detection of radio sources is used to measure the surface error of the Tianma radio telescope. By measuring the surface errors at different elevation angles, a surface compensation model to correct gravitational deformation is established. Observation results shows that the efficiency reduction caused by the gravitational deformation can be effectively compensated by loading this model on the active surface, especially at high and low elevations. A dual-beam calibration scheme is further used to remove atmospheric background fluctuations, which significantly improves data quality at lower elevations. The form and order of the perturbation modes and data processing are optimized to improve measurement accuracy. This paper presents the first attempt to apply the wavefront perturbation method to large radio telescopes and demonstrates its capacity and effectiveness in telescope runtime surface measurement and maintenance.

Trying to achieve the best surface accuracy control with the fewest actuators, this article mainly studies the distribution of actuators and the method of panel design. The influence of the number of faulty actuators on the accuracy of the surface shape is demonstrated. In addition, the method incorporating a triangular panel, node index and the fitting solution method of a single panel is also given. This method provides a reference for the design and realization of an active surface or a deformable sub-reflector for high performance large aperture radio telescopes.

For the frequency standard signal transmission of radio telescope observation stations, a phase-stabilized transmission device is designed for both cable and fiber transmission. In this paper, based on previous studies, the device is installed for practical application, including cable transmission from hydrogen room of TianMa Radio Telescope (TMRT) to VGOS telescope and fiber transmission from hydrogen room of TMRT to Sheshan 25m radio telescope. Phase stability and delay are analyzed. The results show that the phase stability of the frequency standard signal is improved by more than 100 times with the phase-stabilized transmission device. The group delay and delay residuals of phase calibration (PCAL) signals are decreased. This is of great significance for Very Long Baseline Interference (VLBI) observations and high-frequency observations.

The troposphere is one of the main factors affecting the accuracy of all kinds of earth and air observations. Water vapor radiometer(WVR) is a traditional means of atmospheric detection. In this paper, WVR in TianMa radio telescope (TMRT) station is used to analyze TMRT's atmospheric refraction. Besides, rainfall data is statistically analyzed. Research on these two work is very important for improving the observation efficiency of large radio telescopes.

Teaching quality is the lifeline and core competitiveness of the survival and development of higher vocational colleges. Student evaluation plays an important role in the monitoring of teaching quality. Based on the analysis of the existing teaching evaluation system and its results, this paper proposes a multi-dimensional teaching evaluation information system based on quantitative teaching evaluation index system and intelligent analysis function. The system has been tested and run by a university, and its feasibility and effectiveness have been verified. It provides a reference scheme for other universities to build a multi-dimensional evaluation system based on the characteristics of the subject.

This paper proposes an active sub-reflector suitable for large radio telescopes, which can compensate both of the deformation of the main reflector and sub-reflector position offsets. The mathematical formula of the main reflector deformation compensated by the sub-reflector is deduced based on Cassegrain and Gregory antenna structures. The position of the sub-reflector is adjustable to compensate for defocusing errors on high and low elevations, which are mainly caused by the deformation of the sub-reflector supporting legs. In this paper, the method of obtaining the optimum position of the sub-reflector from the aperture phase by the interferometric method is introduced. The actual measurement is verified on the Tianma 65m radio telescope, which provides a new way to diagnose the position error of the sub-reflector.

This paper focuses on the measurement of the main reflector gravity deformation and sub-reflector position change on Tianma 65 m (TM65 m) radio telescope. Firstly the paper summarizes the methods of principal measurement. Microwave holography and cross scan pattern are disscussed. Then the gravity deformation of the main reflector over the entire elevation measured by VLBI method is discribed. The measurement accuracy is also estimated. At last, the gravity model is constructed and compared with the simulation. They agree with each other. The formulas along with the simulation give a description between the offsets of feed, sub-reflector and the aperture phase. The sub-reflector position ofTM65 m is obtained by the least square method that applied on the aperutre phase and the formulas. The sub-reflector positions measured are consistent with that of the traditional amplitude method in X , Y and Z directions. This method provides a different way to measure the position model of the sub-reflector.

In this paper, a 1.5GHz PSFTS (phase stabilized frequency transmission system) based on optical fiber link is described. Through this system, phase calibration can be realized. The principle of PSFTS is analyzed first. And then PSFTS's performance is tested in the laboratory in high and low temperature box. Also the system's performance is measured through buried fiber link. Results show that the real-time compensation mode can improve the phase stability more than 130 times in comparison with the uncompensated mode. In order to solve problems of deterioration of frequency stability and phase noise, a high stability crystal vibration phase lock module is also introduced into this system. Through multiple sets of test data, the frequency stability and phase noise has got obvious improvement. This system will be applied to TMRT (Shanghai TianMa 65 meters radio telescope) system for high precision of astronomical observations.

In the paper, the main factors influencing pointing precision of large radio telescopes are discussed. Then the TianMa radio telescope (TM65 m) is selected for demonstration. The methods of detecting and separating the pointing errors which produce in all the segments from the subreflector to the track rail of the telescope are introduced. They includes: (1) half power point tracking to evaluate the overall antenna pointing error; (2) detecting the pointing error due to position changing of the subreflector support; (3) detecting the deviation of the antenna mount due to temperature changing; (4) detecting the asynchronization of the mechanical axis and the encode axis; (5) high precision pointing modeling based on the uneveness of track rail. A few measurement methods and their respective results are discussed.

Microwave holography is a valuable technique used in the diagnostics and adjustment of large antennas. A brief outline of the technique is given first. Then detail simulations for surface deviation and sub-reflectorr offsets solving method that applied on the TianMa 65 m are described. After several rounds of adjustments, a reflector surface accuracy 0.28 mm and repeated measurement error 0.13 mm were achieved for the TM65 antenna. At last the antenna efficiency on Ka band was measured at elevations between 45 and 60 degrees. The efficiency improved from 37% to 56% when the active surface model is loaded that is consistent with the theoretical predictions.