A Low Earth Orbit(LEO)constellation augmenting satellite navigation is important in the future development of Global Navigation Satellite System(GNSS).GNSS augmented by LEO constellations can improve not only the accu...A Low Earth Orbit(LEO)constellation augmenting satellite navigation is important in the future development of Global Navigation Satellite System(GNSS).GNSS augmented by LEO constellations can improve not only the accuracy of Positioning,Navigation,and Timing(PNT),but also the consistency and reliability of secure PNT system.This paper mainly analyzes the diverse demands of different PNT users for LEO augmented GNSS,including the precision demand in real-time,the availability demand in special areas,the navigation signal enhancement demand in complex electromagnetic environments,and the integrity demand with high security.Correspondingly,the possible contributions of LEO constellations to PNT performance are analyzed from multiple aspects.A particular attention is paid to the special PNT user requirements that cannot be fulfilled with existing GNSS,such as the PNT service demand in the polar regions and the onboard GNSS orbit determination demand of some LEO satellites.The key technologies to be considered in the constellation design,function realization,and payload development of the LEO-augmented navigation system are summarized.展开更多
This paper addresses the problem of sensor search scheduling in the complicated space environment faced by the low-earth orbit constellation.Several search scheduling methods based on the commonly used information gai...This paper addresses the problem of sensor search scheduling in the complicated space environment faced by the low-earth orbit constellation.Several search scheduling methods based on the commonly used information gain are compared via simulations first.Then a novel search scheduling method in the scenarios of uncertainty observation is proposed based on the global Shannon information gain and beta density based uncertainty model.Simulation results indicate that the beta density model serves a good option for solving the problem of target acquisition in the complicated space environments.展开更多
Spaceborne global navigation satellite system(GNSS)has significantly revolutionized the development of autonomous orbit determination techniques for low Earth orbit satellites for decades.Using a state-of-the-art comb...Spaceborne global navigation satellite system(GNSS)has significantly revolutionized the development of autonomous orbit determination techniques for low Earth orbit satellites for decades.Using a state-of-the-art combination of GNSS observations and satellite dynamics,the absolute orbit determination for a single satellite reached a precision of 1 cm.Relative orbit determination(i.e.,precise baseline determination)for the dual satellites reached a precision of 1 mm.This paper reviews the recent advancements in GNSS products,observation processing,satellite gravitational and non-gravitational force modeling,and precise orbit determination methods.These key aspects have increased the precision of the orbit determination to fulfill the requirements of various scientific objectives.Finally,recommendations are made to further investigate multi-GNSS combinations,satellite high-fidelity geometric models,geometric offset calibration,and comprehensive orbit determination strategies for satellite constellations.展开更多
Low-Earth Orbit Satellite Constellations(LEO-SCs)provide global,high-speed,and low latency Internet access services,which bridges the digital divide in the remote areas.As inter-satellite links are not supported in in...Low-Earth Orbit Satellite Constellations(LEO-SCs)provide global,high-speed,and low latency Internet access services,which bridges the digital divide in the remote areas.As inter-satellite links are not supported in initial deployment(i.e.the Starlink),the communication between satellites is based on ground stations with radio frequency signals.Due to the rapid movement of satellites,this hybrid topology of LEO-SCs and ground stations is time-varying,which imposes a major challenge to uninterrupted service provisioning and network management.In this paper,we focus on solving two notable problems in such a ground station-assisted LEO-SC topology,i.e.,traffic engineering and fast reroute,to guarantee that the packets are forwarded in a balanced and uninterrupted manner.Specifically,we employ segment routing to support the arbitrary path routing in LEO-SCs.To solve the traffic engineering problem,we proposed two source routings with traffic splitting algorithms,Delay-Bounded Traffic Splitting(DBTS)and DBTS+,where DBTS equally splits a flow and DBTS+favors shorter paths.Simu-lation results show that DBTS+can achieve about 30%lower maximum satellite load at the cost of about 10%more delay.To guarantee the fast recovery of failures,two fast reroute mechanisms,Loop-Free Alternate(LFA)and LFA+,are studied,where LFA pre-computes an alternate next-hop as a backup while LFA+finds a 2-segment backup path.We show that LFA+can increase the percentage of protection coverage by about 15%.展开更多
基金funded by the National Natural Science Foundation of China(Grant No.42388102No.41931076)+1 种基金the National Key Research and Development Program of China(Grant No.2020YFB0505800)the Laoshan Laboratory(Grant No.LSKJ202205101).
文摘A Low Earth Orbit(LEO)constellation augmenting satellite navigation is important in the future development of Global Navigation Satellite System(GNSS).GNSS augmented by LEO constellations can improve not only the accuracy of Positioning,Navigation,and Timing(PNT),but also the consistency and reliability of secure PNT system.This paper mainly analyzes the diverse demands of different PNT users for LEO augmented GNSS,including the precision demand in real-time,the availability demand in special areas,the navigation signal enhancement demand in complex electromagnetic environments,and the integrity demand with high security.Correspondingly,the possible contributions of LEO constellations to PNT performance are analyzed from multiple aspects.A particular attention is paid to the special PNT user requirements that cannot be fulfilled with existing GNSS,such as the PNT service demand in the polar regions and the onboard GNSS orbit determination demand of some LEO satellites.The key technologies to be considered in the constellation design,function realization,and payload development of the LEO-augmented navigation system are summarized.
基金supported by the National Defense Pre-research Foundation (9140A21041110KG0148)
文摘This paper addresses the problem of sensor search scheduling in the complicated space environment faced by the low-earth orbit constellation.Several search scheduling methods based on the commonly used information gain are compared via simulations first.Then a novel search scheduling method in the scenarios of uncertainty observation is proposed based on the global Shannon information gain and beta density based uncertainty model.Simulation results indicate that the beta density model serves a good option for solving the problem of target acquisition in the complicated space environments.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant Nos.XDA30010000 and XDA30010300).
文摘Spaceborne global navigation satellite system(GNSS)has significantly revolutionized the development of autonomous orbit determination techniques for low Earth orbit satellites for decades.Using a state-of-the-art combination of GNSS observations and satellite dynamics,the absolute orbit determination for a single satellite reached a precision of 1 cm.Relative orbit determination(i.e.,precise baseline determination)for the dual satellites reached a precision of 1 mm.This paper reviews the recent advancements in GNSS products,observation processing,satellite gravitational and non-gravitational force modeling,and precise orbit determination methods.These key aspects have increased the precision of the orbit determination to fulfill the requirements of various scientific objectives.Finally,recommendations are made to further investigate multi-GNSS combinations,satellite high-fidelity geometric models,geometric offset calibration,and comprehensive orbit determination strategies for satellite constellations.
文摘Low-Earth Orbit Satellite Constellations(LEO-SCs)provide global,high-speed,and low latency Internet access services,which bridges the digital divide in the remote areas.As inter-satellite links are not supported in initial deployment(i.e.the Starlink),the communication between satellites is based on ground stations with radio frequency signals.Due to the rapid movement of satellites,this hybrid topology of LEO-SCs and ground stations is time-varying,which imposes a major challenge to uninterrupted service provisioning and network management.In this paper,we focus on solving two notable problems in such a ground station-assisted LEO-SC topology,i.e.,traffic engineering and fast reroute,to guarantee that the packets are forwarded in a balanced and uninterrupted manner.Specifically,we employ segment routing to support the arbitrary path routing in LEO-SCs.To solve the traffic engineering problem,we proposed two source routings with traffic splitting algorithms,Delay-Bounded Traffic Splitting(DBTS)and DBTS+,where DBTS equally splits a flow and DBTS+favors shorter paths.Simu-lation results show that DBTS+can achieve about 30%lower maximum satellite load at the cost of about 10%more delay.To guarantee the fast recovery of failures,two fast reroute mechanisms,Loop-Free Alternate(LFA)and LFA+,are studied,where LFA pre-computes an alternate next-hop as a backup while LFA+finds a 2-segment backup path.We show that LFA+can increase the percentage of protection coverage by about 15%.
