Research On Real-time Correction Method Of Laser Ranging Prediction For Noncooperative Target

With the sustaining human space activities,more and more space debris exist in orbit,collision risk is higher and higher,high-precision measurement of space debris is the important way of promoting target precision monitoring and early warning.Laser ranging technology is being applied to non-cooperative tar-get(space debris)high precision measurement because of its high precision.At present,the orbital predictions of non-cooperative targets are usually based on the two-line element(TLE)and the SGP4 orbital prediction model,containing a big bias.In addition,the laser ranging of space debris is a diffuse reflection process,making the echo signal weak,having higher requirements on the direction and signal noise ratio,which limits the success rate of ranging,embodying in the following two aspects:firstly,the apparent position deviation makes laser pulse can't hit the target accurately and echo photons can't reach the receiver field of single photon detector,secondly,the distance deviation of orbit prediction gives rise to poor range gate controling leading to the low signal noise ratio(SNR)or the detector being always unable to respond to echo photons.For this pur-pose,this paper studies the real-time correction method of the orbit prediction for non-cooperative targets,and mainly completes the following workFirst of all,the combination of the SGP4 predictive model and the method of optical aberration correction based on satellite laser ranging CPF,implements the non-cooperative target orbit prediction for laser ranging,including visual position of target(lag quantity),laser's fronted launch direction,laser round-trip flight time is the foundation of the follow-up orbit prediction real-time correction workSecondly,it analyses the main factors that lead to the large deviation in the TLE prediction of non-cooperative target.It is believed that the main rea-son is that the atmospheric drag model adopted by SGP4 model is reduced to a constant resistance parameter B*,while atmospheric drag is actually related to atmospheric density,target posture and drag coefficient.According to the measuring phenomena,the deviation is mainly existing in the direction of the trace,namely the position deviation of the elliptical orbit in its orbit.Therefore,the method of reducing the main deviation of the time element is proposed.Be?cause of the extrapolation and coordinate transformation of SGP4 model,it is a complicated nonlinear process,and the parameter search method is used to find the optimal time element deviation in a certain passing segment.In order to verify the validity of this method in theory,using the visual position prediction generated by the high-precision CPF of the laser ranging satellite as the simu-lated observation value for the time element deviation searching.The results show that(1)the optimal time element deviation exists;(2)according to the orbital prediction after the correction by the optimal time element deviation,the appar-ent position deviation is significantly reduced and the fluctuation amplitude is decreased,and the prediction distance deviation is also significantly reduced.(3)there is no significant difference between the initial 1 minute data and the whole segment data in searching the optimal time element deviation,which can meet the real-time demand.Then,the measured data is tested,and the results show that,after the correction by the time element deviation,the apparent position deviation decreases significantly and the fluctuation amplitude decreases,which proves the effectiveness of the method.