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As an important means of anti-ballistic missile weapons ,it is used for early detection of missiles, determination of missile parameters, determination of targets to be attacked by missiles, and provides advance warning for national strategic defence decisions. It plays an important role in ballistic missile defence system. The early warning satellites located in space are not limited by the curvature of the earth, they are condescending and have a wide coverage area, which can detect ballistic missiles moving in space early. Multi-band joint early warning has become an important development trend of space-based early warning. Space-based ultraviolet early warning is an effective early warning means that uses the ultraviolet radiation of missiles to detect missile targets in the active phase and re-entry phase. Based on the normalized detection rate, this paper deduces the formula for calculating the detection distance according to the sensitivity of the UV detector, and simulates the relationship between the system aperture and the detection distance ,as well as the relationship between the detection signal-to-noise ratio and the target temperature .The simulation results show that the system aperture of 50mm can meet the requirement of the signal-to-noise ratio of 6. With the increase of the target temperature ,the signal-to-noise ratio increases rapidly. According to the simulation results, a geostationary orbit space-based ultraviolet early warning system scheme is designed. The optical system adopts the off-axis total reflection type, and the working spectrum is 200~300nm, 220~290nm, 230~280nm, 255~275nm. For the spectrum segment ,four 9°×9° fields of view are spliced to achieve the requirement that the system’s field of view is not less than 18°×18°, ensuring global and earth limb coverage. Four cameras achieve full field of view coverage. Filters with different spectral are placed in front of the focal plane of each camera. The filters are installed on the filter wheel and driven by a motor to realize real-time monitoring of the world and obtain different spectral bands. Sections of experimental date to support background and target characterization studies. The structure design of this scheme is novel and has certain reference significance.
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