Autonomous Orbit Determination Of Satellite Constellations In The Earth-moon System And A Proposed VLBI Constellation

With the rapid development of space technology,mankind's deep space exploration activities are increasing.Compared with near-Earth space exploration missions,deep-space missions have the characteristics of the probe being far away from the Earth,extended communication time,complex space environment,and difficult measurement and control.All of these have put forward higher requirements on the observation methods and the navigation capabilities of the detector.It remains difficult to meet the requirements of deep space exploration missions by providing navigation services to probes through ground systems relying on traditional observation methods such as ranging and Doppler measurement.The existing global navigation constellation system GNSS is not powerful and sensitive enough to provide navigation services for deep space probe missions and also suffers from the problem of poor geometry and poor coverage ability.In the future,there will be more and more spacecraft operating in orbit,and a denser space measurement and control network will be required on the ground.This will seriously increase the labor cost and resource cost of the ground system,and the ground aerospace measurement and control system is easy to become the target of attack in wartime,thus posing a threat to mission security.With such a background,a navigation satellite constellation based on some special orbits of the Earth-Moon system is proposed.Different from the previous navigation satellite constellations which mainly utilize the collinear libration points,the constellation proposed here rely on stable orbits even in the ‘real' Earth-Moon system.As a result,no orbit control.Non-artificial-maneuver makes the long-term accumulation of inter-satellite range data between navigation satellites possible.Thus,the autonomous orbit determination(AOD)relying solely on the inter-satellite range data is possible.In this thesis,we test the AOD ability of the proposed constellation and analyze the orbit determination accuracy.Further,taking a probe on an Earth-Moon transfer orbit as an example,we also analyze the orbit determination accuracy of the probe relying on the navigation signal from the navigation satellite,and analyze the error of the orbit determination results caused by the position error of the navigation satellite.VLBI is an observation technology based on the principle of interference that has been successfully applied to astronomical observations in 1967.Among the current astronomical observation methods,VLBI's spatial resolution is the highest,and it has achieved great results in imaging.The resolution of VLBI is mainly determined by the observation frequency and the length of the baseline.In order to obtain higher-precision observation data,at a fixed frequency,the length of the baseline is extended to break through the limitation of the size of the Earth.Placing the VLBI base station on a satellite in outer space has become a natural choice for improving the resolution of the VLBI,namely the space VLBI technology.If we can design a stable space VLBI constellation that can operate autonomously for a long time,the high-precision measurement of space VLBI technology can effectively solve the problem of autonomous navigation of deep space probes.A conceptual Space very long baseline interferometry(SVLBI)constellation in the Earth-Moon system is introduced in this paper.The constellation consists of two kinds of special orbits: dynamical substitutes(DSs)of the triangular libration points and distant retrograde orbits(DRO).The base stations of the SVLBI constellation can form a baseline with each other and can also form baselines with stations on the ground.Due to the longer baseline between the base stations,the observation precision obtained by the SVLBI constellation proposed in this paper is much higher than that of the ground VLBI(GVLBI).Due to their stability,the DSs and DRO are ideal orbits for locating the navigation satellites.The SVLBI constellation not only can advance radio astronomy,but also can serve as a navigation system for human activities in the Earth-Moon system and even in the solar system.Theoretically,due to the special dynamic properties of these two special orbits,the orbits of the navigation satellites can be autonomously determined by only using the inter-satellite range data.As a result,no support from the ground stations is needed,and the SVLBI constellation can autonomously perform their roles in space.The space VLBI constellation mentioned in this article can avoid the atmospheric error item that has a greater impact on VLBI observations and improves the observation accuracy as all the base stations are in outer space.The structure of the paper is as follows:The first chapter introduces the background and significance of the thesis,and the research progress of deep space exploration,autonomous navigation and translational point navigation at home and abroad.It should be pointed out that the proposed constellation configuration based on the large-amplitude dynamics of the Earth-Moon triangle translational point and the DRO orbital stable DRO orbit is the first time.The second chapter is the theoretical basis of the full text research work.It briefly introduces the space-time coordinates,actual force models,orbit determination methods and VLBI related basic knowledge used in the orbit determination of this article.The third chapter first introduces two special types of orbits involved in this work: the DSs orbit and DRO orbit near the triangular libration points under the actual force model.Taking the positioning of various DSs orbits and their orbits as examples.A detailed analysis of AOD of various constellation combinations and orbit determination accuracy based on inter-satellite links is given;The fourth chapter takes the space VLBI constellation positioned on the DSs orbit and DRO orbit as the space base station,takes the lunar detector's orbit determination as an example,using radar ranging data and VLBI technology,it conducted the orbit determination test and analyzed its orbit determination accuracyThe fifth chapter summarizes and prospects the work of this article..Studies in this thesis show that(1)The AOD of the dynamical substitutes based on the inter-satellite range data is feasible.The dependence of the orbit determination(OD)accuracy on the length of data,the initial point,and the out-of-plane component.(a)For a short length of data,the OD accuracy in R and T direction of the dynamical substitutes is of the same magnitude but is one or two magnitudes better than that in N direction.Nevertheless,the difference improves for a long length of data.(b)The OD accuracy varies with respect to the initial point.For a longer length of data,the viriation becomes smoother and smaller.The reason for this difference lies in the fact that a short length of data can only cover a small portion of dynamical substitutes and the OD accuracy is sensitive to different initial points,but a long length of data can cover nearly the whole dynamical substitutes orbit.(c)For a shorter length of data,the OD accuracy may reach the same level of accuracy of the observation data when Z-direction component of the orbit.The accuracy of orbit determination can be determined by sampling arc,initial point selection and Z direction amplitude parameter,and the orbit determination can be carried out automatically and efficiently.(2)Taking the lunar exploration mission as an example,under the actual force model,the inter-satellite link data is used to realize the autonomous navigation of the lunar probe,thereby verifying the feasibility of autonomous navigation of the navigation constellation.The research results show that the navigation accuracy reaches the observation accuracy,and the accuracy in the N direction is an order of magnitude worse than that in the R and T directions.Adding a random error to the navigation satellite as a system error is equivalent to the site error of the ground station.Under the ‘real' force model,using the inter-satellite link data,the navigation constellation still can still achieve autonomous navigation for the lunar probe,and the accuracy reaches the observation accuracy,while the accuracy in the N direction is still an order of magnitude worse than the R and T directions.(3)We construct a space VLBI constellation with a stable navigation constellation in this thesis.The VLBI antenna base station is placed on the navigation constellation,so that a long baseline can be formed between the navigation stars.It can achieve a high angular resolution.For the navigation of deep space probes,high-precision observation data can be obtained.Through verification,the ground-moon transfer section is used as the reference task.Under the actual force model,the VLBI delay data and delay rate data are used to realize the detector's Autonomous navigation,and navigation accuracy meets the needs.