Principle And Experimental Study On Attitude Inversion Of Space Object Based On Analysis Of Time Series Spectral Signal

As the space environment is gradually developed,the space object situational awareness with its related fields have become research hotspots,including the inversion research on the information of the types,shapes,orbits,and attitudes of space objects,and attitude inversion is particularly important.The thesis aims at the attitude inversion of non-cooperative space objects under long-distance observation with space-based observation system,considering that the surface material is degraded by the radiation effect,a Bidirectional Reflectance Distribution Function(BRDF)model of cosineweighted function is constructed to characterize the optical reflection characteristics of the material before and after radiation.In this paper,based on the time-series spectral signals,a mathematical model and method for solving the material reflection characteristic parameters and attitude parameters respectively is derived,and the attitude information is estimated using genetic algorithm,which is verified through simulation and measurement experiments at last.The specific research contents of the paper are as follows:(1)Investigate the space environment where the space object is located and analyze the material damage caused by the radiation effect,thus the degradation of the material sample of space object is simulated through the ground-based radiation test.Then the spectral BRDF of the material before and after radiation is measured and a BRDF model of cosine-weighted function is constructed to fit the measured data,which established the prerequisites and foundation of attitude inversion.(2)By combining the mathematical model and optimization algorithm,the attitude inversion principle is derived: The first step,the space object in three-axis stabilization state is equivalent to a two-facet model,and a BRDF model of cosine-weighed function is introduced to describe the spectral reflection characteristics of complex material surfaces.Based on the observed time-series spectral signal,the product of area and spectral BRDF of the two-facet can be inverted using linear optimization algorithm.The second step,in order to minimize the interconnection influence of the two-facet on attitude estimate,the two-facet reflection characteristics difference is set up to select the optimum wavelength based on the maximum of the difference.The third step,as the attitude of the space object changes,the model of time-series signal is constructed based on the two-facet model parameters in the optimum wavelength.The goal function is defined as the error between the model data and the measured data,and the optimization variables are attitude parameters,which will be estimated using genetic algorithm(GA).(3)Comprehensively consider the satellite model’s geometric structure,satellite orbit,background radiation and other factors,combined with the BRDF modeling data of the material before and after radiation,the time-series spectral signal model is derived based on radiometry.The surface element analysis method is used to simulate the timeseries spectral signals of on-orbit object before and after radiation,which will be used as inputs to invert the attitude so as to verify the algorithm.Gaussian noise with different signal-noise ratio(SNR)is added on the simulated signal to analyze the influence of noise on attitude inversion,thus the boundary of the algorithm can be determined.(4)Based on the laboratory environment,the measurement platform was built to get the photometric signal reflected by the satellite model,which will finally verify the algorithm of attitude inversion.