The Tian Ma Telescope (TM) is the largest fully steerable radio telescope in Asia. It has a primary reflector of 65-m in diameter with a shaped Cassegrain configuration. The primary reflector of the TM is an active surface with 1104 actuators for the 1008 surface panels. The panels of the telescope are divided into 18 rings, and 24 fan sections. Each section includes three sub-sections. The active surface system adopts TCP/IP Ethernet network and RS-485 bus as a dominating mode of communication. The control software works on the Windows system, and adopts the object-oriented technology. The photogrammetry and phase-coherent holography has been used to set the surface to about 0.3mm at the rigging angle. The FEM model is testing now. The Out-of-Focus holography and other techniques will be used to modify the dynamic surface deformation.
KEYWORDS: Temperature metrology, Antennas, Radio telescopes, Error analysis, Temperature metrology, Thermal effects, Telescopes, Space telescopes, Sensors, Data modeling, Thermal modeling
Aimed at the alidade of TM65m antenna, the distributions of temperature field and effects of thermal deformations on pointing accuracy were analyzed based on thermometers and inclinometer. The alidade temperature and cross-elevation tilt were recorded for one year when the antenna was at different azimuth and elevation angles. And, the emphasis is on studying the data of sunny days in summer and winter during the antenna parked its home position (azimuth angle=155°, elevation angle=90°). The results show the maximum temperature difference between day and night is 14.6 °C in summer and is 27 °C in winter. In winter, the larger temperature difference, shorter sunshine time and later sunrise contribute to the temperature variation per unit time is larger. In addition, pointing offset was checked by scanning polestar for continuous 24 hours. From the results obtained so far, it seems that the elevation offset caused by the alidade temperature variation is more than 20 arcsec from 8:00 am to 10:00 am. The research results provide a base for the enhancement of pointing accuracy.
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