Research On The Key Technologies Of Positioning On Medium And High Earth Orbit User Based On Inter-satellite Links

The position accuracy of the groud-based method is not high enough for users in medium and high orbit,and the effective signal of the satellite navigation system is difficult to cover these areas.Positioning for users in medium and high orbit using inter-satellite link of navigation constellation can solve the realistic demands that the limited coverage and accuracy,can provide an example for other users of the inter-satellite link extension application,and can prepare technologies for the future application like space-based network.Theoretically,as long as the user can collect enough ranging values,the user position can be solved in a similar manner as GPS.However,the inter-satellite link is designed for the navigation satellite,which has the exact orbit and time synchronization information.The extended user does not have this condition,and the ranging conditions between the time-division system of the inter-satellite link and the code-division system of GPS are not consistent.Therefore,achieve the user position is steal a problem.So that the basic problem of this paper is how to locate the medium and high orbit spacecraft using inter-satellite links without changing the hardware of the navigation satellite.On this issue,the paper focuses on the following key technical problems:1.Feasibility problem of positioning.Navigation satellite launches time-division narrow beam signal,and the satellites are in high-speed relative motion,so that the signal beam is sparse and dynamic for the whole space.Moreover,the user can not complete the positioning unless they can collect enough effective measurement signals.Therefore,the feasibility analysis is the key problem in the positioning of medium and high orbit spacecraft.2.Dectection problem of received signal.The detection of the effective signal is the prerequisite for obtaining the observation value.Since the extended user does not have the precise orbit and time information,it increases the range of the signal search.The time-division system also requires the user to acquire the signal in a short time with high detection probability.Therefore,detection of the received signal is a key problem in the positioning of medium and high orbit spacecraft.3.Direct solution problem of position.Although there are a large number of navigation satellites,the extened user only receive one satellite signal at the same time,witch is not the same as users equiped with GPS.Further more,ranging satellites and ranging order also will impact the positioning accuracy.Therefore,the direct solution is the key problem in the positioning of medium and high orbit spacecraft.4.Joint solution problem of position.Although positioning can be achieved only by the ranging results between the user and the satellites,the ranging error and position datum error are relatively large.Fortunately,the precise range and clock error of navigaition satellite can be measured using inter-satellite ranging.It is possible to improve the positioning accuracy if we can make full use of the inter-satellite mesurement information.Therefore,the combination solution of user ranging and inter-satellite ranging is the key problem in the positioning of medium and high orbit spacecraft.In order to solve the above-mentioned key technical problems,a new method of position feasibility analysis based on SSV and ephemeris fitting is proposed,a high-sensitivity and fast acquisition method based on carrier phase compensation is proposed,a multi-epoch solution method based on clustering satellite selection is proposed,and a method of ephemeris error correction based inter-satellite ranging is proposed.These technical methods can solve the above four key technical problems.They all passed the theoretical analysis and simulation verification,which proved the feasibility and effectiveness of the technology.They can provide reference for the research and development of the relevant load of medium and high orbit users.