| Wide Angle Aurora Imager(WAAI) is the first Far Ultraviolet(FUV) imaging telescope with a wide field of view(Fo V) in the low Earth orbit. There are two similar cameras which are fixed centrosymmetricly. The off-axis reflective optical system is introduced. Each camera has 68°×10° field of view and the integrated Fo V of the two centrosymmetric cameras is 130°×10°. In order to have sufficient field of view to cover the entire polar region from for the 830 km low orbit mission, the two camera of WAAI is rotated around +Y-axis and the final Fo V is 130°×130°. WAAI attempts to use the available auroral signal in the FUV wavelength band with the N2 LBH bands, so it is sensitive in the spectral region from 140~180 nm. To reject UV from wavelengths shorter than 140 nm, we used a 2 mm thick Ba F2 window. Ba F2 is known to leak in the longer wavelength region when hot. The operating temperature range of the Ba F2 filter is from 107 ℃ to 140 ℃ and its cut-off band is approximately 140 nm. The thermal control system of WAAI is necessary to guarantee that the WAAI could undergo long-term work and the thermal design of Ba F2 filter is the most important technology.In this paper, the main study work is to design a thermal control system of WAAI. Firstly, the development and signification of aurora observation was introduced, and also the present research status of Ultraviolet imager instruments throughout the world was summarized. Secondly, depend on the characteristic work mode of WAAI, the paper provided a method to calculate the external heat fluxes with changing attitudes frequently. This method could calculate real-time geomagnetic latitudes and attitudes. After predigest the cameras, the external heat fluxes were obtained by mapping plane theory and Monte Carlo Method(MCM).Thirdly, study the thermal design and test of Ba F2 filter in detail to maintain the filter’s temperature and cut-off band. Then based on the system sensitivity, under the design variables analysis of the thermal resistance in the overall heat transfer path from the transmission filter to optical bench, sensitive design variables of the optical bench temperature was found. Then three thermal designs of the high temperature filter were implemented depending on the above analysis result. The optimization thermal design project of Ba F2 filter was chosen depend on experimental results and corresponding transmission test was carried on from 140nm~180nm.And then, the concrete thermal control subsystem of WAAI was introduced. The finite element model(FEM) was built by IDEAS/TMG and thermal analysis was performed. Thermal analysis results indicated that the temperature of the internal components could satisfy the requirement and the thermal control subsystem could provide suitable environmental temperature for WAAI.Finally, depend on the thermal design and thermal analysis of WAAI, thermal test was carried on. Under the cold and hot extreme cases, the filter average temperature could respectively reach 107℃ and 140℃, and the temperature stability was less than 1.5℃/2min. The temperature indexes of other components also could be satisfied. The thermal test results had shown that thermal design of WAAI was correct and thermal analysis was also credible. |
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