| As the fast development of deep space exploration of human,manned mission to Mars has been planned for Mars exploration in future.When facing the manned mission to Mars,it is very important to have the ability to achieve autonomous communication,navigation and observation and keep communication link between Mars and earth stations continuous connectivity,get a large capacity of communication link for a manned Mars hot spot.In view of the above problems,the article studied from the following aspects which Mars regional constellation design,spatial characteristic parameter of relay link between Earth and Mars,and topology control strategies of Sun-Earth system Lagrange points as relay between Earth and Mars deep space communication,main work and innovative results include:1.Aim at the problem of low time resolution for the Mars Sun-synchronous regression orbit,the design of a multi approximate revisit period characteristics of Mars Sun-synchronous regression orbit was proposed.According to the properties of the regressive orbit,the approximate revisiting periodic function was devised,by traversing the approximate revisit period in the entire finite field,to discriminate relative distance between subspaces number of revisit intervals and basic intersection distance,we have got multi approximate revisiting characteristics of Sun-synchronous regression orbit.Using the optimal approximate revisiting period,to compare with classical synchronous regression orbits,the design improved the time resolution of satellite observation on the surface of Mars.2.For manned Mars exploration,we may first choose to land near the equator of Mars.In order to achieve the largest communication coverage of hot landing areas and the maximum visible time of ground stations and Mars constellations,we proposed a Mars regional constellation design scheme based on NSGA-Ⅱ optimization.In this scheme,the design of the Mars constellation was modeled as the multi-objective optimization model of the largest coverage of the constellation to the target area and the maximum visible time of the earth’s earth station to the constellation.Using the optimized NSGA-Ⅱ algorithm based on the concept of Pareto,the simulation results showed that compared to the classical Walker constellation,this scheme has better performance in the revisit time,more than double coverage and other aspects.3.In view of superior conjunction of earth and Mars,how to quickly establish a relay link based on Lagrange point L4/L5 when the communication link was interrupted by solar radiation.According to the Euler theorem of the rigid body,through the rotation of the pointing vector of L4/L5 to Mars in different coordinate systems,we derived the theoretical expression of the space characteristic parameters of L4/L5 pointing to Mars.The simulation results of theoretical deduction were compared with the STK simulation,and have higher fitting degree.This study provided basis and guidance to establish rapid interplanetary link based on L4/L5 relay between Earth and Mars.At the same time,it provided a reference for the establishment of interplanetary relay link.4.When the Lagrange point L4/L5 was used as the relay node of the deep space communication network between Earth and Mars,how to design the L4/L5 topology control strategy to maximize the fire performance of deep space network,a topology control strategy based on 0-1 programming model to select direct one hop link or relay based two hop link was proposed.From the two aspects of the maximum throughput and the maximum visible time of the link,we adopted the control strategy based on the 0-1 programming model respectively to get the optimal solution under the constraint condition.The simulation results showed that the performance of the proposed method was better than a simple direct one hop link and a simple two hop link based on Lagrange point relay. |
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