Study On Quantum Ranging Used In The Field Of Inter-satellite Distance Measurement For Satellite Formation Flying

Combination of quantum information theory and traditional techniques can improve the performance of classical systems,currently,it has become a hot topic in the fields of electronic information,communication,and computer.Combination of quantum theory and radar detection produces quantum radar,which can improve the detection ability of radar system;combination of quantum theory and communication produces quantum cryptographic system,which can enhance the security of communication channel;combination of quantum theory and computer greets the birth of quantum computer,which would increase the operating rate of computer.Compared to traditional single satellite,satellite formation flying(SFF)has obvious advantages of higher reliability,stronger flexibility,and lower cost.Thus,space missions using SFF have become popular in recent years.Increasing the ranging accuracy can strengthen the system stability of SFF and is of great importance to that system.As quantum ranging can beat the conventional bounds to the accuracy of measurements,this dissertation pays attention to quantum ranging that is applied in inter-satellite distance measurement for SFF.The main content consists of the following parts:1.This dissertation analyzes the complementary relationship between quantum ranging and SFF:on one hand,quantum ranging can beat the conventional bounds to the accuracy of measurements,then it can meet the strict requirement of inter-satellite ranging accuracy for SFF;on the other hand,SFF is a suitable platform for the distribution of quantum entanglement.Considering these two aspects,the key points of this dissertation are determined.2.In order to apply quantum ranging into the field of inter-satellite ranging for SFF,this dissertation proposes two quantum sensors,i.e.,DPQR-type and TQR-type sensors.Based on the common qunatum ranging technique,this dissertation proposes the DPQR-type sensor and analyses both the measurement principle and the ranging accuracy of it,then discovers a disadvantage:in order to measure distance d,the DPQR-type sensor introduces a traditional type of ranging device and eventually causes a worse accuracy.Thus,thisdissertation proposes a novel TQR-type sensor,which offsets the measurement process of idler light path using the triangle geometry of satellite formation,and can solve the disadvantage of DPQR-type.3.Currently,works on quantum ranging merely consider the scenario of static target,then,this dissertation studies the effect of relative motion on the performance of quantum ranging,and proposes some solutions.During condition of rapid relative motion,Doppler shift can invalidate the result of coincidence measurement;while during condition of slow relative motion,the "accumulated time effect"(i.e.,the accumualted profile becomes distorted and broadened)becomes the major influencing factor,and the ambiguity velocity can be used to evaluate whether the above effect can affect the accuracy of quantum ranging.If relative speed between targets and measurement platform exceeded the ambiguity velocity,the accumulated profile would be distorted,which causes a worse ranging accuracy.Lastly,theoretical analysis shows a time-varying delay can be introduced to solve those two major puzzles.4.Because the performance of quantum ranging becomes poor during satellite missions of distant formation flight that are located at low Earth orbit(LEO),this dissertation analyzes its essential cause and proposes two solutions.We find that there always exists a rapid relative motion among the above missions,which causes a large variation in the difference in signal and idler light paths during Ta,and eventually causes a worse performance of quantum ranging.In order to solve this problem,this dissertation proposes two types of techniques,i.e.,shortening the accumulated time Ta and introducing a time-varying delay.Using a specific configuration of entangled photons source,Ta is shortened to 0.126 s and the ranging accuracy can be improved.However,the improved one is still worse than what we expect.Combining the shortened value of Ta of 0.126 s,we can cancel the effect of relative motion by introducing a time-varying delay,and obtain a narrow accumulated profile determining a ranging accuracy which is only restricted by the resolution of coincidence system.