Research On Key Navigation Technology Of Lunar Orbiting Satellite Gnss Receiver

In recent years,the field of space exploration in China has developed continuously,and lunar exploration activities have become more and more frequent.With the increasing number of lunar orbiting spacecraft,it is very important to obtain its position,velocity,time(PVT)and other information timely and accurately.However,relying on the ground station resources is far from meeting the actual needs.If the Global Navigation Satellite System(GNSS)receiver can be used to process the received GNSS signal in real time to realize autonomous navigation,it will certainly reduce the pressure on the ground station and the operation cost greatly.Considering the problems of low received signal power of lunar orbiting satellites,a few numbers of visible GNSS satellites and poor geometric distribution,the feasibility of lunar orbiting GNSS receiver,and high sensitivity and fast acquisition algorithm of GNSS navigation signal,and positioning algorithm of multi-constellation integrated GNSS satellites are studied.The main research contents are as follows:1)Considering the problems of a few numbers of visible satellites and poor geometric distribution of lunar orbit GNSS receiver,the feasibility of lunar orbit GNSS receiver is studied.This paper studies the theory of GNSS satellite orbit,analyzes the visibility and coverage principle of GNSS receiver in lunar orbit,and introduces the functional modules involved in building the inter satellite communication link model of GNSS receiver by using Satellite Tool Kit(STK).By building the inter satellite communication link model of GNSS receiver,the signal power received by GNSS receiver in lunar orbit at each time,and the visibility of the receiver to GNSS satellite at different threshold levels,and the coverage and positioning accuracy error of the receiver at each time are analyzed.2)Considering the problems of low received signal power and slow acquisition speed of lunar orbit GNSS receiver,the GNSS navigation signal acquisition algorithm is studied.The common methods to improve the acquisition sensitivity,coherent integration method and incoherent integration method are studied.The influence of the two methods on the SNR gain and the existing problems are analyzed.Two classical acquisition algorithms,serial search acquisition(SSA)algorithm and parallel code phase acquisition(PCA)algorithm,and parallel code phase acquisition based on sparse Fourier transform(SFT-PCA)algorithm with higher operation efficiency are studied,the computational performance and capture performance of the three algorithms are analyzed respectively.Considering the problem that PCA algorithm has great number of FFT operation points and SFT-PCA algorithm mixes signals and noise in time domain,resulting in poor filtering effect,a noise reduction for simplified parallel code phase acquisition(NR-SPCA)algorithm with noise reduction is proposed.As the simulation results show,the operational efficiency and acquisition sensitivity of NRSPCA algorithm are better than PCA algorithm.3)Considering the problem of a few visible satellites in lunar orbit GNSS receiver,the positioning algorithm of multi-constellation integrated GNSS satellites is studied.The theory of GNSS satellite orbit and the coordinate system of multi-constellation space-time system are introduced respectively.Considering the problem of a few numbers of visible satellites in lunar orbit satellite receiver,the least square positioning method of multi-constellation integrated GNSS and Kalman filter positioning method of multi-constellation integrated GNSS are studied.Through the actual measurement and experimental simulation of the receiver module,the positioning performance of the two algorithms is compared and analyzed,and the necessity of multi-constellation integrated GNSS positioning under the condition of less visible satellites is verified.The above research work,to a certain extent,verifies the feasibility of building a spaceborne GNSS receiver in lunar orbit,and provides some theoretical and technical support for future lunar exploration missions.