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The Multi-Spectral Camera is one of main payloads of ZY-3 satellite, which was launched in 2012 in China, and was used to land surveying, resources exploring, and 3D mapping. The Multi-Spectral Camera provides color image for the map. Due to the applying to mapping, the stability of elements of interior orientation becomes more important.
The Multi-Spectral camera applies a three mirror off-axis optical system, so reflectors of the camera are key factors for imaging quality. Under the condition of space, the change of thermal environment will lead to distortion of opt-structure, so the location of the reflectors will change, which affects the imaging quality and the stability of elements of interior orientation. So the first problem for the mechanical design is to insure the stability of reflectors' position throughout alignment, experiments, and launch. In one word, the structure of tree mirror off-axis optical system must have excellent stability; include mechanics and thermal stability.
Based on the imaging quality of the Multi-Spectral Camera, the paper analyzes the requirement of the opt-structure's stability, and presents an effective thermal-structure stabilizing design of the camera. The camera uses a design of unloading structure on the principle of flexible hinge. There are four mounting feet on the Camera. One mounting foot constraints all the six freedoms, flexible hinges on the other three of mounting feet can release the freedom at the thermal-distortion direction, so the camera is quasi statically determinate system on the satellite. The structure can release the thermal-distortion of the satellite effectively, when the temperature of the satellite frame is ranged from 25℃ to 15℃ on-orbit, besides the structure can provide enough stiffness. Combining the FME method with the experiments, it is validated that the flexible hinge structure can satisfied the stability requirement of the opt-structure.
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