Research On The Thermo-optical Problems Of All-Day Star Sensor

With the development of celestial navigation technology,the star sensor technology for obtaining precise navigation based on the position of stars has also been rapidly developed.At present,the research field of star sensor is gradually shifting from space to near ground.Due to the serious atmospheric interference near ground and the more complicated environment,more stringent requirements are put forward for its optical system.The temperature change is an important factor affecting the optical performance of the star sensor throughout the day.Therefore,by studying the thermo-optical problems of the all-day star sensor,the athermalization technology is used to reduce the influence of wide temperature changes on the optical performance of the star sensor,thereby significantly improving the navigation and positioning accuracy of the all-day star sensor.The development of celestial navigation technology is of great significance.This article first investigates the development status of the all-day time star sensor technology and athermalization technology at home and abroad.Because temperature changes are the key to the navigation and positioning accuracy of the allday time star sensor,the focus is on how to improve the all-day time star sensor.The temperature adaptability of the optical system of the sensor is athermalized by the use of an optical-mechanical combination method.The research content of this article mainly includes the following parts:(1)The changes in the refractive index of the optical elements,the surface shape of the elements,and the spacing between the optical elements in the optical system with temperature changes are carried out,and the reasons why the optical performance of the optical system changes with the temperature are analyzed.These research contents can be As the theoretical basis for the athermal design of the optical system.(2)Analysis and summary of the basic principles,advantages and disadvantages of the three athermal design methods: mechanical passive,mechanical active,optical passive and refraction-differential hybrid;analysis and summary of the structure when using the differential principle to achieve athermal design The principle of material selection,and the mechanical components that can achieve the goal are listed according to specific needs;based on the optical passive athermal design method,the thermal properties of some commonly used infrared materials and visible light materials are summarized,which can provide data for athermal design support.(3)According to the working characteristics of the airborne all-day star sensor optical system,the sky background light radiation characteristics and the target star’s radiation characteristics are analyzed,and it is found that the sky background light has strong radiation intensity in the visible light region,but in the near-infrared spectrum.There is a large attenuation,and the radiation intensity of the target star is stronger than the sky background light radiation intensity after 600 nm.Therefore,combined with this feature,900nm～1700nm is selected as the working spectrum of the optical system of this paper;and then a detection is selected according to the needs Based on the performance of the selected detector,the key optical parameters of the optical system,such as the aperture,focal length and field of view,are analyzed.Finally,the key parameters of the optical system are selected based on the system detection signal-to-noise ratio.(4)According to the selected optical system design parameters,optimize the design of the airborne all-day star sensor optical system at room temperature and pressure,and then optimize the optical system from the perspective of optical and mechanical integration.The final result It means that the optical system designed by this method can meet the requirements of use in the range of-40℃～+60℃.