Study On Space-Based Optical Orbit Determination Method For Space Targets

Long-range,wide-range,short revisit cycle space target surveillance capability is key to ensuring the security of space assets and the sustainable use of orbital resources.The use of optical means to achieve space target surveillance has received widespread attention in recent years because of its obvious advantages in terms of detection dis-tance,surveillance range,system size and power consumption.Orbit determination algorithm is the core algorithm of space-based optical space target surveillance system to achieve the surveillance function.The study of the orbit determination algorithm is important for understanding the performance of the surveillance system and the design of the surveillance system index parameters.This paper takes the space-based optical space target surveillance system as the research background,and starts the research from four aspects:the approximation model of the initial orbit determination algorithm,the orbit determination algorithm based on the optimal state estimation,the influence of the observation conditions on the determination accuracy,and the ability of the large field of view space-based optical system to monitor the synchronous orbit targets,and has achieved certain research results.The main contents and conclusions are as follows:Chapter 3 of the thesis studies two approximation models,the small eccentricity approximation of the target orbit and the linear motion approximation of the target un-der a short observation arc,for the initial orbit determination algorithm approximation model.A level of correction for eccentricity is added to the circular approximation model,which greatly reduces the systematic error.Deriving the orbit determination equation with respect to the target state as linear from minimizing the measurement vector residuals in a short observation arc using a linear motion approximation model.The necessity of two reference vectors being perpendicular to each other and unit vec-tors is proved.It is pointed out that the extended Laplace algorithm and the fork product measurement model have the problem of missing weight coefficients.Chapter 4 of the thesis derives the covariance matrix with respect to the target state using orbit determination equations that are linear with respect to the target state for shorter observed arc segments.Calculate the covariance matrix obtained from a single arc segment.Calculating a priori estimates of the next observed arc segment using Monte Carlo sampling allows it to have the ability to handle problems with perturbation.Multi-observation arc data orbit determination algorithm by Kalman filtering.Realize the initial orbit determination,tracking and cataloging in one for the long arc segments with perturbation problem of orbit determination algorithm.Chapter 5 of the thesis analyzes the effect of observation conditions on the orbit determination.Firstly,the theory of positioning error estimation is proposed based on the feature that the target position uncertainty is mainly concentrated in the axis of the line-of-sight vector.The positioning accuracy is quantified by an upper limit of posi-tioning error with a clear physical meaning.Find the numerical correspondence with other methods of evaluating observation conditions that have no corresponding physical meaning.The observation conditions are divided into two parts:observation geometry and observation error,observation arc length,and observation interval affected by ob-server parameters.The upper limit of positioning error is used to quantify the influence of observation conditions on the determination accuracy.Three variables are proposed to describe the arbitrary possible observation geometry of the observer and target with small eccentricity in terms of the observer inclination and the right ascension of the observer and target in the rotated coordinate system.The phenomenon of poor deter-mination accuracy when the observer and the target are in the same line with the Earth is found.Empirical relations are given for the upper limit of the positioning error pro-portional to the observation error,proportional to the 0.5th power of the observation interval,and proportional to the-2.5th power of the observation arc length under the condition of constant observation interval.Chapter 6 of the thesis proposes an observation plan for surveilling the entire syn-chronous orbit with a short revisit period for a large field of view space-based optical observer.And the initial orbit determination and preliminary cataloging algorithm in this scenario is implemented using the theoretical results of the orbit determination al-gorithm.The observation plan of staring at the mean angle of the virtual target with 7.5~°orbital inclination is proposed to ensure a certain observation arc length for the whole synchronous orbit target.The working model of one observation for one gaze point is proposed based on the calculation of the effective observation range.The field of view of the observer is divided into two parts:long-and wide-field of view.The wide field of view needs to be greater than 18~°by the geometric relationship.The conversion re-lationship from the long field of view to the continuous observation arc length to the orbit determination effect is given.In simulation experiments,a single 20°×40°field-of-view observer with a 5 arc-second observation error and a 10-second observation interval can achieve a fixing accuracy of about 98%of the synchronous orbital target’s average kilometer-level positioning error over three observer orbital periods.