Research Of High Orbit Spacecraft Positioning Technology Based On GNSS

With the rapid increase in the activity of human's exploration of space,the ground measurement and control capacity has reached a saturation state.The autonomous positioning function has become an essential function of spacecraft.Morden deep space explorarions include Chinese lunar exploration project and other high orbit(HO)flight application proposes urgent demand of GNSS positioning.Low orbit spacecraft positioning by using global navigation satellite system(GNSS)is gradually mature.For the HO spacecraft GNSS positioning,the disadvantageous factors are: little number of visible satellites,poor geometric accuracy factor(GDOP)and low signal Carrier-Power-to-Noise Density Ratio(CNR).In order to solve the problems encountered in high orbit spacecraft positioning,this dissertation is explored and studied from the following aspects: feasibility evaluation of HO spacecraft positioning by GNSS,inter-satellite link(ISL)optimization design for HO positioning,BeiDou satellite navigation system(BDS)autonomous positioning by other GNSS signals and BDS satellite on board receiver optimization design,and the signal processing algorithms of GNSS and ISL signals jointed receiving.(1)Based on the multi-constellation joint positioning,a feasibility analysis and evaluation method is proposed to demonstrate the feasibility of GNSS mainlobe and sidelobe signal receiving on deep space weak signal environment for the HO spacecraft positioning.This feasibility is evaluated by the parameters of the number of visible satellites,the signal receiving CNR,and GDOP,with various configurations of the four major GNSS systems: the American GPS,the Chinese BDS,the Russian GLONASS and the European Galileo satellite navigation systems.The research results show that: the power of the existing sidelobe signal is too low for the receiver to acquisit the signal of which the CNR is lower than its threshold,any GNSS joint mode can not be completed as only the mainlobe signal can be used;On the premise of the constellation design or the receiver's performance improved,combination of three GNSS systems already can meet the lunar spacecrafts' position demand on its orbit for the full time;GDOP of 4 systems combined is 16.93% less than 3 systems combined.The GPS,BDS and Galileo combined mode reaches the best GDOP performance.Conclusions provide the reference for the design of multi-constellation combined receiver for HO spacecraft.(2)The method of HO spacecraft positioning using ISL wide beam signal is proposed,to solve the problem that the GNSS signal is so weak that the position effect is poor.Based on the weighted distance root mean square(wdrms)optimization algorithm,the ISL signal observation performances on both the navigation constellation and the HO spacecraft are jointed optimized.An ISL wide beam mode and a new annular beam antenna is proposed to support the HO spacecraft positioning and inter satellite communication.By the comparation of simulation data and the on orbit flight experimental data of Chang'E No.5,the results show that: the proposed ISL design brings batter performance than GNSS positioning,and the demonds of HO spacecraft positioning and ISL ranging and communication functions are met at the same time.(3)To minimaize the geometric distance root mean square,a method of BDS satellites autonomous positioning by GPS/GLONASS signals is proposed,to solve the problem that on the situation when satellite to ground communication is interrupted,satellites of BDS can not autonomous positioning.The Doppler frequency shift,Doppler shift rate,band rejection,number of visible satellite,signal receiving CNR and GDOP are restrictively calculated and joninted evaluated to analysis the BDS onboard receiver's performance of GPS/GLONASS signals receiving on MEO,GEO,and IGSO.On above three orbits,respectively,the receiver front-end design parameters for the optimal signal receiving performance are obtained.Three optimal antenna models are respectively proposed,providing reference for the BDS onboard satellite navigation receiver design.(4)Firstly,a fast positioning algorithm based on the combination of ISL and GNSS is proposed,to solve the problem of demending in time for first positioning in HO weak GNSS signals receiving.Theoretical research results show that: the first positioning time is reduced to the 1/6 of the normal condition by this new algorithm;Secondly,an improved vector delay locked loop(VDLL)algorithm based on GNSS weak signal tracking combined with ISL strong signal is proposed,to solve the problem of low VDLL tracking precision for GNSS weak signals;Thirdly,an unbiased tracking algorithm based on GNSS VDLL assisted ISL Scalar Delay Lock Loop(SDLL)is proposed,to solve the problem of tracking bias of traditional VDLL when the number of observation satellites is more than four.At last,for solving the problem that the weak signal tracking precision of HO spacecraft is seriously deteriorated by non-ideal channel,the expression of group delay estimation precision of dual side band tracking algorithm under the non-ideal channel has been theoretically derived.The loss of group delay estimation accuracy for BOC and BPSK modulations have been analyzed with the power type and the cosine type group delay,then the suggestion is proposed.Major achievements of the thesis support the research of HO spacecraft GNSS positioning national natural science fundation.The achievements have been applied to the multi-GNSS receiver,the ISL signal generator and the multi-system navigation signal generator,which provide theoretical supports for the HO spacecraft to get rid of the ground tracking station network's limitation and realize the real time high precision positioning in future.