Low Earth Orbit(LEO)satellites,with their wide coverage and large number,have gradually become a crucial platform and means for navigation and positioning services.Compared to other LEO constellations,Starlink has ove...Low Earth Orbit(LEO)satellites,with their wide coverage and large number,have gradually become a crucial platform and means for navigation and positioning services.Compared to other LEO constellations,Starlink has over 6000 satellites in orbit,and its signals contain synchronous sequences usable for pseudo-range positioning.Thus,it has a potential serve as an alternative to Global Navigation Satellite System(GNSS)for providing Positioning,Navigation,and Timing(PNT)services.Compared to parabolic antennas and electronically scanned phased array antennas for receiving Starlink signals,wide-beam antennas(such as Low-Noise Block(LNB)downconverters)can be used to achieve low-cost multi-satellite tracking.However,it also encounters the issues of distinguishing between multiple satellite signals and low received signal power,which requires high-sensitivity detection.Moreover,there are some other issues such as unknown signal transmission time and real-time satellite orbits,thereby causing failure to navigation.Accordingly,this study focuses on LEO constellations represented by Starlink,proposes a joint pseudo-range and Doppler positioning method for Starlink satellite Signals of Opportunity(SOP)based on the comprehensive utilization of signals and information from LEO satellites.Moreover,this study analyzes the signal detection capability and satellite isolation method,examines the algorithm’s orbital error suppression performance,and establishes the concept of Equivalent Position Dilution of Precision(EPDOP)S_(EPDOP)for joint pseudo-range and Doppler positioning.In the experiment because Starlink satellite signals are not available in China,we take the advantage of Iridium NEXT satellites’global seamless coverage,utilize an algorithm to get pseudo-range observations with the Iridium NEXT signals,and then combine them with Starlink Doppler observations to achieve the joint pseudo-range and Doppler positioning of LEO satellites’SOPs.The experiment results demonstrate that when relying on Starlink Doppler observations for positioning,the proposed method achieves Two-Dimensional(2D)positioning accuracy of 3.6 m and Three-Dimensional(3D)positioning accuracy of 6.2 m.Compared to existing Starlink positioning algorithms based on parabolic antennas and electronically scanned phased array antennas,this method improves the accuracy by at least 35.7%.Additionally,Iridium NEXT signals are used to validate the performance of the proposed algorithm for joint pseudo-range and Doppler positioning.In a 40 km long-baseline scenario,the algorithm achieved a 2D positioning accuracy of 24 m and a 3D positioning accuracy of 41 m with Iridium NEXT satellite pseudo-range and Doppler measurements.展开更多
We theoretically investigate the Doppler effect on optical bistability in an N-type active Raman gain atomic system inside an optical ring cavity. It is shown that the Doppler effect can greatly enhance the dispersion...We theoretically investigate the Doppler effect on optical bistability in an N-type active Raman gain atomic system inside an optical ring cavity. It is shown that the Doppler effect can greatly enhance the dispersion and thus create the bistable behaviour or greatly increase the bistable region, which has been known as the positive Doppler effect on optical bistability. In addition, we find that a positive Doppler effect can change optical bistability from the hybrid dispersion-gain type to a dispersive type.展开更多
To provide backup and supplementation for the Global Navigation Satellite System(GNSS),Doppler shift from Low Earth Orbit(LEO)satellites can be used as signals of opportunity to provide positioning,navigation,and timi...To provide backup and supplementation for the Global Navigation Satellite System(GNSS),Doppler shift from Low Earth Orbit(LEO)satellites can be used as signals of opportunity to provide positioning,navigation,and timing service.In this contribution,we frst investigate the model and performance of instantaneous velocity determination and positioning with LEO satellites.Given a LEO constellation with 288 satellites,we simulate Doppler shift observations at nine multi-GNSS experiment stations.Owing to the lower orbit,the performance of LEO velocity determination is much more sensitive to the initial receiver position error than that of GNSS.Statistical results show that with the initial receiver position error increased from 0.1 to 10 m,the Root Mean Square Errors(RMSEs)increase from 0.73 to 2.65 cm/s,0.68 to 2.96 cm/s,and 1.67 to 4.15 cm/s in the east,north,and up directions,respectively.The performances with GPS are compared with GPS+LEO,and it is found that LEO Doppler shift observations contribute to GPS velocity determination.As for LEO Doppler positioning,even if more than 30 visible LEO satellites are available,the position dilution of precision values can reach several hundreds.Assuming that the error of LEO Doppler measurements is 0.01 m/s,the instantaneous Doppler positioning accuracy can achieve about a few meters,which is comparable to that of GNSS pseudorange positioning.A constant velocity model is adopted for state transition.Static LEO Doppler positioning results show that an accuracy at centimeter to decimeter level can be achieved after solution convergence.For a static simulated kinematic positioning test,the RMSEs range from a few decimeters to several meters in diferent regions by giving diferent constraints.For a dynamic positioning test,the RMSEs are about 2–3 m in high latitude region.展开更多
基金support is received from the Strategic Priority Research Program of the Chinese Academy of Sciences(XDA0350101)the Project(E2M4140306).
文摘Low Earth Orbit(LEO)satellites,with their wide coverage and large number,have gradually become a crucial platform and means for navigation and positioning services.Compared to other LEO constellations,Starlink has over 6000 satellites in orbit,and its signals contain synchronous sequences usable for pseudo-range positioning.Thus,it has a potential serve as an alternative to Global Navigation Satellite System(GNSS)for providing Positioning,Navigation,and Timing(PNT)services.Compared to parabolic antennas and electronically scanned phased array antennas for receiving Starlink signals,wide-beam antennas(such as Low-Noise Block(LNB)downconverters)can be used to achieve low-cost multi-satellite tracking.However,it also encounters the issues of distinguishing between multiple satellite signals and low received signal power,which requires high-sensitivity detection.Moreover,there are some other issues such as unknown signal transmission time and real-time satellite orbits,thereby causing failure to navigation.Accordingly,this study focuses on LEO constellations represented by Starlink,proposes a joint pseudo-range and Doppler positioning method for Starlink satellite Signals of Opportunity(SOP)based on the comprehensive utilization of signals and information from LEO satellites.Moreover,this study analyzes the signal detection capability and satellite isolation method,examines the algorithm’s orbital error suppression performance,and establishes the concept of Equivalent Position Dilution of Precision(EPDOP)S_(EPDOP)for joint pseudo-range and Doppler positioning.In the experiment because Starlink satellite signals are not available in China,we take the advantage of Iridium NEXT satellites’global seamless coverage,utilize an algorithm to get pseudo-range observations with the Iridium NEXT signals,and then combine them with Starlink Doppler observations to achieve the joint pseudo-range and Doppler positioning of LEO satellites’SOPs.The experiment results demonstrate that when relying on Starlink Doppler observations for positioning,the proposed method achieves Two-Dimensional(2D)positioning accuracy of 3.6 m and Three-Dimensional(3D)positioning accuracy of 6.2 m.Compared to existing Starlink positioning algorithms based on parabolic antennas and electronically scanned phased array antennas,this method improves the accuracy by at least 35.7%.Additionally,Iridium NEXT signals are used to validate the performance of the proposed algorithm for joint pseudo-range and Doppler positioning.In a 40 km long-baseline scenario,the algorithm achieved a 2D positioning accuracy of 24 m and a 3D positioning accuracy of 41 m with Iridium NEXT satellite pseudo-range and Doppler measurements.
基金Project supported by the National Natural Science Foundation of China (Grant No. 60978013)the Shanghai Rising Star Project,China (Grant No. 11QA1407400)
文摘We theoretically investigate the Doppler effect on optical bistability in an N-type active Raman gain atomic system inside an optical ring cavity. It is shown that the Doppler effect can greatly enhance the dispersion and thus create the bistable behaviour or greatly increase the bistable region, which has been known as the positive Doppler effect on optical bistability. In addition, we find that a positive Doppler effect can change optical bistability from the hybrid dispersion-gain type to a dispersive type.
基金the Fund of National Key Research and Development Program of China(No.2022YFB3903902)the National Science Fund for Distinguished Young Scholars(No.41825009)the Key Research and Development Program of Hubei Province(No.2022BAA054).
文摘To provide backup and supplementation for the Global Navigation Satellite System(GNSS),Doppler shift from Low Earth Orbit(LEO)satellites can be used as signals of opportunity to provide positioning,navigation,and timing service.In this contribution,we frst investigate the model and performance of instantaneous velocity determination and positioning with LEO satellites.Given a LEO constellation with 288 satellites,we simulate Doppler shift observations at nine multi-GNSS experiment stations.Owing to the lower orbit,the performance of LEO velocity determination is much more sensitive to the initial receiver position error than that of GNSS.Statistical results show that with the initial receiver position error increased from 0.1 to 10 m,the Root Mean Square Errors(RMSEs)increase from 0.73 to 2.65 cm/s,0.68 to 2.96 cm/s,and 1.67 to 4.15 cm/s in the east,north,and up directions,respectively.The performances with GPS are compared with GPS+LEO,and it is found that LEO Doppler shift observations contribute to GPS velocity determination.As for LEO Doppler positioning,even if more than 30 visible LEO satellites are available,the position dilution of precision values can reach several hundreds.Assuming that the error of LEO Doppler measurements is 0.01 m/s,the instantaneous Doppler positioning accuracy can achieve about a few meters,which is comparable to that of GNSS pseudorange positioning.A constant velocity model is adopted for state transition.Static LEO Doppler positioning results show that an accuracy at centimeter to decimeter level can be achieved after solution convergence.For a static simulated kinematic positioning test,the RMSEs range from a few decimeters to several meters in diferent regions by giving diferent constraints.For a dynamic positioning test,the RMSEs are about 2–3 m in high latitude region.
