This paper proposes new quasi-periodic orbits around Earth–Moon collinear libration points using solar sails.By including the time-varying sail orientation in the linearized equations of motion for the circular restr...This paper proposes new quasi-periodic orbits around Earth–Moon collinear libration points using solar sails.By including the time-varying sail orientation in the linearized equations of motion for the circular restricted three-body problem(CR3BP),four types of quasi-periodic orbits(two types around L1 and two types around L2)were formulated.Among them,one type of orbit around L2 realizes a considerably small geometry variation while ensuring visibility from the Earth if(and only if)the sail acceleration due to solar radiation pressure is approximately of a certain magnitude,which is much smaller than that assumed in several previous studies.This means that only small solar sails can remain in the vicinity of L2 for a long time without propellant consumption.The orbits designed in the linearized CR3BP can be translated into nonlinear CR3BP and high-fidelity ephemeris models without losing geometrical characteristics.In this study,new quasi-periodic orbits are formulated,and their characteristics are discussed.Furthermore,their extendibility to higher-fidelity dynamic models was verified using numerical examples.展开更多
Trajectory corrections for lunar flyby transfers to Sun–Earth/Moon libration point orbits(LPOs)with continuous thrusts are investigated using an ephemeris model.The lunar flyby transfer has special geometrical and dy...Trajectory corrections for lunar flyby transfers to Sun–Earth/Moon libration point orbits(LPOs)with continuous thrusts are investigated using an ephemeris model.The lunar flyby transfer has special geometrical and dynamical structures;therefore,its trajectory correction strategy is considerably different from that of previous studies and should be specifically designed.In this paper,we first propose a control strategy based on the backstepping technique with a dead-band scheme using an ephemeris model.The initial error caused by the launch time error is considered.Since the perturbed transfers significantly diverge from the reference transfers after the spacecraft passes by the Moon,we adopt two sets of control parameters in two portions before and after the lunar flyby,respectively.Subsequently,practical constraints owing to the navigation and propellant systems are introduced in the dynamical model of the trajectory correction.Using a prograde type 2 orbit as an example,numerical simulations show that our control strategy can efficiently address trajectory corrections for lunar flyby transfers with different practical constraints.In addition,we analyze the effects of the navigation intervals and dead-band scheme on trajectory corrections.Finally,trajectory corrections for different lunar flyby transfers are depicted and compared.展开更多
The far side of the moon is a unique place for some scientific investigations.Chang'e 4 is a Chinese lunar far side landing exploration mission.Relay communication satellite,named as Queqiao,is an important and in...The far side of the moon is a unique place for some scientific investigations.Chang'e 4 is a Chinese lunar far side landing exploration mission.Relay communication satellite,named as Queqiao,is an important and innovative part of Chang'e 4 mission.It can provide relay communication to the lander and the rover operating on the lunar far side to maintain their contacts with Earth.It was launched by LM-4C launch vehicle at the Xichang Satellite Launch Center on May 21,2018.After five precise orbit controls and a journey of more than 20 days,Queqiao inserted into final halo mission orbit around Earth-moon libration point 2,located about 65,000 km beyond the moon.It is the world's first communication satellite operating in that orbit.Up to now,Queqiao worked very well and provided reliable,continuous communication relay service for the lander and the rover to ensure the mission success of Chang'e 4 exploration mission.Via Queqiao,the lander and the rover were controlled to work by ground stations and obtained a great amount of scientific data.The mission overview,operation orbit selection,relay communication system design and flight profile were introduced in this article.展开更多
文摘This paper proposes new quasi-periodic orbits around Earth–Moon collinear libration points using solar sails.By including the time-varying sail orientation in the linearized equations of motion for the circular restricted three-body problem(CR3BP),four types of quasi-periodic orbits(two types around L1 and two types around L2)were formulated.Among them,one type of orbit around L2 realizes a considerably small geometry variation while ensuring visibility from the Earth if(and only if)the sail acceleration due to solar radiation pressure is approximately of a certain magnitude,which is much smaller than that assumed in several previous studies.This means that only small solar sails can remain in the vicinity of L2 for a long time without propellant consumption.The orbits designed in the linearized CR3BP can be translated into nonlinear CR3BP and high-fidelity ephemeris models without losing geometrical characteristics.In this study,new quasi-periodic orbits are formulated,and their characteristics are discussed.Furthermore,their extendibility to higher-fidelity dynamic models was verified using numerical examples.
基金supported by the Canada Research Chair Program under Grant No.950-230883.
文摘Trajectory corrections for lunar flyby transfers to Sun–Earth/Moon libration point orbits(LPOs)with continuous thrusts are investigated using an ephemeris model.The lunar flyby transfer has special geometrical and dynamical structures;therefore,its trajectory correction strategy is considerably different from that of previous studies and should be specifically designed.In this paper,we first propose a control strategy based on the backstepping technique with a dead-band scheme using an ephemeris model.The initial error caused by the launch time error is considered.Since the perturbed transfers significantly diverge from the reference transfers after the spacecraft passes by the Moon,we adopt two sets of control parameters in two portions before and after the lunar flyby,respectively.Subsequently,practical constraints owing to the navigation and propellant systems are introduced in the dynamical model of the trajectory correction.Using a prograde type 2 orbit as an example,numerical simulations show that our control strategy can efficiently address trajectory corrections for lunar flyby transfers with different practical constraints.In addition,we analyze the effects of the navigation intervals and dead-band scheme on trajectory corrections.Finally,trajectory corrections for different lunar flyby transfers are depicted and compared.
文摘The far side of the moon is a unique place for some scientific investigations.Chang'e 4 is a Chinese lunar far side landing exploration mission.Relay communication satellite,named as Queqiao,is an important and innovative part of Chang'e 4 mission.It can provide relay communication to the lander and the rover operating on the lunar far side to maintain their contacts with Earth.It was launched by LM-4C launch vehicle at the Xichang Satellite Launch Center on May 21,2018.After five precise orbit controls and a journey of more than 20 days,Queqiao inserted into final halo mission orbit around Earth-moon libration point 2,located about 65,000 km beyond the moon.It is the world's first communication satellite operating in that orbit.Up to now,Queqiao worked very well and provided reliable,continuous communication relay service for the lander and the rover to ensure the mission success of Chang'e 4 exploration mission.Via Queqiao,the lander and the rover were controlled to work by ground stations and obtained a great amount of scientific data.The mission overview,operation orbit selection,relay communication system design and flight profile were introduced in this article.
