Photometric Luminosity Analysis Of Space Debris

Space debris is the castoff left in space by human spaceflight activities,in-cluding rocket debris,retired spacecraft and debris decomposed after spacecraft collision,etc.The number of space debris increases year by year.Not only does it make orbital resources very scarce,but also greatly increases the risk of space-craft collision.Up to now,space debris has become a hot issue of global concern.If there is no intervention,space debris will become one of the fundamental prob-lems restricting human space exploration activities.Space monitoring is one of the contents of space situational awareness and an important support of space situational awareness.Ground-based optical observation of space debris is one of the important projects studied by scholars at home and abroad.Based on the observation of ground-based optical telescopes,the luminosity changes of s-pace debris can be obtained,which has important applications in the tracking,recognition and classification of space debris.The data acquisition of ground-based optical telescopes is limited by obser-vation conditions such as observation equipment,weather and visibility period.Space debris research demand is different,the observation pattern will be differ-ent.Sometimes it needs a multiple target for short time observation.Sometimes it needs for individual goals for long time observation.Sometimes it needs to multiple observation stations to joint observation,especially for some special phenomena.Observation data can only be obtained when special phenomena occur and under observable conditions.For some research needs,we want to get photometric data of space debris,requires a lot of time and equipment resources.Therefore,a method of simulating photometric data is proposed in this paper to solve the problem of some insufficient measured data.This paper mainly includes the following contents:Firstly,the orbit and attitude system of space debris are introduced.Two ways of representation of the orbit of space debris,namely Cartesian root number and Kepler root number,are introduced.The conversion formula of the two orbital roots is derived.The coordinate system of space debris and their transforma-tion relations are introduced,including the geocentric inertial coordinate system,the geocentric fixed coordinate system,the orbital coordinate system and the ontology coordinate system.In this paper,three attitude descriptions of space debris are introduced,namely Euler Angle?YPR Angle and quaternion,and their conversion formulas are derived.Secondly,according to the optical scattering characteristics of space debris,combined with the characteristics of its shape,orbit,attitude and material,a photometric model of space debris is established.The light variation mechanism of space debris is analyzed,which provides theoretical support for the modeling.The shape of space debris is determined by using the theory of small surface element.The position of space debris is determined by using the TLE orbital prediction model.And the attitude of space debris is expressed by using the quaternion.After analyzing the characteristics of various BRDF models,the Ashikhmin-Shirley model is selected to establish the photometric model of space debris.Then,the effects of various parameters in the luminosity model on the lumi-nosity of space debris are analyzed.By controlling variable method,the shape parameters,orbit parameters,attitude parameters,BRDF model parameters and geographic location of the station are analyzed for influence on simulation light curve.Through the analysis and comparison of the simulation light curve,it shows that the change of the shape parameters will affect the variation of simu-lation luminosity;different orbits will show different shapes of light curves,and the orbit with same altitude of light curves will have similar shapes;attitude parameters have a great influence on the light curve and the shape of the light curve is related to the attitude mode.The parameters of BRDF model are related to the peak phenomenon.The larger the Phong model parameter(nu?nv))the larger the mirror reflection parameter(Rs),and the more obvious the peak phe-nomenon;the longitude of the station determines the time of the peak position,and the latitude determines whether there is a peak and how large the peak is.Finally,real spacecraft is selected to verify the reliability of the simulation model.The attitude control mode of the navigation system is introduced.A GPS satellite and a domestic GEO satellite are selected as simulation objects,and the simulation observation data is compared with the real observation data.The simulation light curve of domestic GEO satellite in one year is also analyzed.Meanwhile,the rotating state and turning state of domestic GEO satellite are simulated.The simulation results show that the simulated light curve is basically consistent with the measured light curve under the normal operation mode.In the rotating state and the turning state,the simulated light curve is basically corresponding to its set state.