Research Of Spectrum Reddening Effect Of The Space Man-made Object

Frequent space activities have caused a large amount of space debris.People pay more and more attention to the protection and prediction of these debris.Therefore,it is particularly important to catalogue and identify unknown space debris.In the past decade or so,spectral observation techniques are increasingly being applied to the inversion,analysis,and identification of various spatial target material compositions.During the research process,the target's reflection spectrum showed a“reddening effect”,which affected the comparison and identification of the material characteristics and morphology by using the target reflection spectrum and the laboratory material spectrum.Therefore,it is necessary to explore and understand the causes of“reddening effect”.The thesis considers that the“reddening effect” is caused by the phase angle,the attitude of the target and the influence of the orbital space environment in the observation process by summarizing the research status at home and abroad.Space environment is an important factor causing reddening effect.It change the physical and chemical properties and surface roughness of materials exposed to spacecraft.Both of them affect the spectral reflectance characteristics of materials.In this thesis,experimental data and computer simulation are combined to explore the effect of material roughness change on satellite spectral “reddening effect”.Firstly,the BRDF model of different roughness states of the material is established based on the relevant experimental data,and then the reflectance spectrum of the satellite target is simulated and calculated.In this thesis,the hemispherical spectral reflectivity of three materials for satellite is measured in laboratory,and the refractive index of the material is inversed according to the Fresnel equation,which is used as the basis for solving the Fresnel reflectivity of the material.The thesis designs some material samples with different roughness by referring to the experimental data of related literatures,in order to simulate the variation in surface roughness of the materials exposed to the space environment.Then the spectrum scattering characteristics of the material with different surface roughness is theoretically modeled.And the spectral scattering characteristics of three common satellite materials with different roughness states are simulated and analyzed.The results show that as the material roughness increases,the spectral scattering range is increase,and the specular reflection spectrum intensity is gradually decrease.When the roughness is different,reflection spectrum morphology of the material is also different.Then,based on the spectral scattering simulation data of the materials on the satellite surface,the whole satellite reflection spectrum signals of the satellite surface materials in different roughness states are simulated.The simulation process consider the influence of the relevant orbits and observation conditions.The simulation results show that the satellite reflection spectrum intensity decreases with the increase of satellite surface roughness.After normalization,the satellite reflection spectrum increases with the increase of wavelength after 600 nm.It is indicated that the change of surface roughness of exposed materials in space environment is one of the reasons for the “reddening effect” of satellites.And,the satellite reflection spectrum signals at different observation times are simulated and calculated.The comparison shows the influence of different observation time on the satellite spectral morphology,which helps us better understand the influence of satellite observation phase angle change on satellite spectral reflectance spectrum.By establishing the material spectral scattering model and related simulation calculations,it is helpful to better understand the influence of the surface roughness variation of the material on the "redness effect" of the satellite spectrum.It provides reference and support for studying the influence of surface material aging on the reflection spectrum in the space environment and inverting the aging of satellite surface materials.