Research On Star Detection Technology Of Interferometric Daytime Star Sensor For Near-earth Application

Star sensor is a widely used attitude measurement element in aerospace field.It has the characteristics of high measurement accuracy,high degree of freedom,strong anti-jamming ability and no accumulated error.However,the star sensor based on the traditional all-sky imaging scheme has some practical problems,such as too strong background noise in the daytime,too low signal-to-noise ratio of star detection,and limited accuracy of star location.The excellent coherence characteristics of stars as small angular diameter targets provide a new idea for the design of star sensors based on the principle of interference,which can effectively solve the problem of limited detection ability of traditional star sensors.This paper studies the star detection technology of interferometric all-sky time star sensor for near-earth application,mainly including the following three aspects:Firstly,the characteristics of stellar target and background radiation transfer are studied.Blackbody radiation law based on star magnitude calibration and MODTRAN simulation software were used to analyze the characteristics of stellar target and sky background,and the contrast irradiance model of stellar target and sky background was established.At the same time,combining with the stokes vector method and polarization degree model of target and background is established polarization contrast model,and uses the Lib Radtran polarization characteristics simulation software to the sky background,and by introducing the complex degree of coherence model,constructed the bandwidth and interferometric imaging stripe star sensors characteristics,the relationship between of star sensor observation for interference bandwidth selection provides the basis.Secondly,the optical design of the interferometric all-sky time star sensor is developed.The initial structure of the interferometric star sensor is selected based on the characteristics of interferometric imaging.According to the working principle of the system,the imaging link model of the interferometric all-sky star sensor is constructed.The initial parameters of the star sensor,such as field of view Angle,focal length and aperture,are determined for the practical application.Using the nonsequential optical design mode of Zemax,the design of the telescope system,the interference module,the imaging system and the overall system are realized.Based on the established optical detection model,the observational SNR of the interferometric star sensor under different input conditions was obtained,and the star detection capacity of the daytime interferometric star sensor was simulated.Finally,the star map simulation of the interferometric all-sky star sensor is carried out.Based on the imaging mechanism of the interferometric all-sky time star sensor,the imaging link model of the system was built by comprehensively considering the characteristics of star target and sky background radiation.The simulation star map of the interferometric all-sky time star sensor was generated by using 2MASS catalogue as the data source.At the same time,to further rise the quality of star map,the orthogonal phase-locked amplification algorithm is used to restore the sequential star map,and the periodic time-varying signals in the interferometric star sensor star map are effectively separated from the irregular noises,and the signal-to-noise ratio is used as the evaluation index to evaluate the image quality of the restored star map.The evaluation results show that the recovered star map can meet the extraction conditions of 7stars.In this paper,the exploration and research of the interferometric all-sky star sensor star detection technology can provide an important technical reserve for the design and application of the new system star sensor based on the principle of interference,and provide reliable technical support for the near-earth application of star sensor technology.