Prototyping and Environmental Experiments of an Aluminum Panel for the Dome A 5m Terahertz Explorer (DATE5)

摘要

Dome A 5m Terahertz Explorer (DATE5) is a proposed telescope to be deployed at Dome A, Antarctica to explore the excellent terahertz observation condition unique to the site. One of the key challenges of the telescope is to realize and maintain the required 10 μm rms overall reflector surface accuracy under the extreme site conditions and unmanned operating mode. Aluminum panels on carbon fiber backup structures is one of the candidate options for the 5 meter main reflector. For aluminum panels, three major technical risks were identified: 1) the large CTE of aluminum causes significant panel deformation due to the large seasonal soak temperature change; 2) internal stress may cause additional surface deformation when operating under a cold environment; 3) reflector panels working at Dome A run high risks of icing (which degrades antenna efficiency and increases noise) and automatic active de-icing mechanisms has to be implemented on the panels. In order to verify the feasibility of the aluminum panels for DATE5 and identify possible technical risks, a prototype panel was fabricated and went through rigorous tests. The manufacture error at the room temperature is 3.2 μm rms, which meets the budget. The panel surface is then measured at various ambient temperatures down to -60°C in a climate chamber using photogrammetric techniques. The additional surface error at the low temperatures is found to be mainly contributed by defocusing error, and the dependence of the panel focal length on temperature is well predictable. No additional surface error caused by internal stress has been observed. Next, the icing condition of the panel is analyzed and a prototype de-icing system based on polyimide film heaters was installed on the panel. The performance of the de-icing system was tested in a climate chamber as well as in the field experiments to simulate a variety of operating environments. The experiments indicate that the power required for de-icing the entire main reflector is less than 1kW and the temperature field produced by the de-icing system has trivial effect on the surface accuracy of the panel. This study indicates that aluminum panels have the potential to meet the reflector surface error budget under the harsh environment of Dome A.