The Space High-cadence Observing Telescope (SHOT) is proposed to operate at the frequency band of 1 ∼ 3 THz. It will have a wide field of view to achieve a large sky area imaging survey and gather more information about the dynamic universe. A prototype telescope with 500 mm aperture will be established and tested at the preliminary stage. The telescope adopts a dual-reflector system. Considering the lightweight design, topology optimization of three cases of reflectors with aluminum, SiC and CFRP are carried out to supply a reference of the initial structure design and material option. In the initial design, the aluminum secondary reflector is supported by a steel cylinder and connected to the support structure of the main reflector using steel tripods. The back side of the main reflector is mostly distributed with triangular holes and supported through three points. The main reflector adopts SiC. To further improve the performance, the multiple-objective size optimization is conducted according to the finite element analysis results. The total weight of the optimal structure is only 8.62 kg, 31% less than the initial design. The surface deformation rms is 2.18 μm by loading gravity and 50 K temperature difference. The stiffness of the structure is also sufficient.
Lidar has been proven to be a powerful tool for the atmospheric detection due to the advantage of high spatial and temporal resolution. And multi-wavelength lidar can obtain more atmospheric optical properties, which can be inverted to the particle microphysical properties. However, in the multi-wavelength lidar, classical transmission beam expanders of simple structure are difficult to achieve simultaneous beam expansion at multiple wavelengths because of the impact brought by chromatic aberration. To solve this problem, we design an off-axis reflective beam expander with only two spherical mirrors and applied it in the multi-wavelength Raman lidar system. The main parameters of the beam expander have been analyzed in detail and optimized by the Zemax software. And we also design a simple mechanical structure for adjustment of the beam expander which was demonstrated experimentally. According to the receiver field-of-view (FOV), the divergence angle of the emitted laser is less than 0.4 mrad. The experimental results show that the beam expander can be applied well in the multi-wavelength Raman lidar system. Keywords: Off-axis beam expander, Multi-wavelength Raman
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