Inter-satellite Time Synchronization and Ranging Link Assignment for Autonomous Navigation Satellite Constellations

2021 ◽  
Author(s):  
Leyuan Sun ◽  
Jun Yang ◽  
Wende Huang ◽  
Laping Xu ◽  
Shaochuan Cao ◽  
...  
Keyword(s):  
Autonomous Navigation ◽  
Time Synchronization ◽  
Navigation Satellite ◽  
Satellite Constellations

scholarly journals Performance evaluation of multi-GNSSs navigation in super synchronous transfer orbit and geostationary earth orbit

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Tao Shi ◽  
Xuebin Zhuang ◽  
Liwei Xie
Keyword(s):  
Global Navigation Satellite System ◽  
Autonomous Navigation ◽  
Satellite System ◽  
Earth Orbit ◽  
Navigation Satellite ◽  
Geostationary Earth Orbit ◽  
Beidou Navigation Satellite System ◽  
Transfer Orbit ◽  
High Orbit ◽  
Global Navigation Satellite

AbstractThe autonomous navigation of the spacecrafts in High Elliptic Orbit (HEO), Geostationary Earth Orbit (GEO) and Geostationary Transfer Orbit (GTO) based on Global Navigation Satellite System (GNSS) are considered feasible in many studies. With the completion of BeiDou Navigation Satellite System with Global Coverage (BDS-3) in 2020, there are at least 130 satellites providing Position, Navigation, and Timing (PNT) services. In this paper, considering the latest CZ-5(Y3) launch scenario of Shijian-20 GEO spacecraft via Super-Synchronous Transfer Orbit (SSTO) in December 2019, the navigation performance based on the latest BeiDou Navigation Satellite System (BDS), Global Positioning System (GPS), Galileo Navigation Satellite System (Galileo) and GLObal NAvigation Satellite System (GLONASS) satellites in 2020 is evaluated, including the number of visible satellites, carrier to noise ratio, Doppler, and Position Dilution of Precision (PDOP). The simulation results show that the GEO/Inclined Geo-Synchronous Orbit (IGSO) navigation satellites of BDS-3 can effectively increase the number of visible satellites and improve the PDOP in the whole launch process of a typical GEO spacecraft, including SSTO and GEO, especially for the GEO spacecraft on the opposite side of Asia-Pacific region. The navigation performance of high orbit spacecrafts based on multi-GNSSs can be significantly improved by the employment of BDS-3. This provides a feasible solution for autonomous navigation of various high orbit spacecrafts, such as SSTO, MEO, GEO, and even Lunar Transfer Orbit (LTO) for the lunar exploration mission.

scholarly journals Practical Modeling of GNSS for Autonomous Vehicles in Urban Environments

Sensors ◽  
2019 ◽  
Vol 19 (19) ◽  
pp. 4236
Author(s):  
Woosik Lee ◽  
Hyojoo Cho ◽  
Seungho Hyeong ◽  
Woojin Chung
Keyword(s):  
Motion Estimation ◽  
Autonomous Vehicles ◽  
Autonomous Navigation ◽  
Urban Environments ◽  
Global Navigation Satellite Systems ◽  
Navigation Satellite ◽  
Key Technology ◽  
Satellite Systems ◽  
Agricultural Robots ◽  
Global Navigation Satellite

Autonomous navigation technology is used in various applications, such as agricultural robots and autonomous vehicles. The key technology for autonomous navigation is ego-motion estimation, which uses various sensors. Wheel encoders and global navigation satellite systems (GNSSs) are widely used in localization for autonomous vehicles, and there are a few quantitative strategies for handling the information obtained through their sensors. In many cases, the modeling of uncertainty and sensor fusion depends on the experience of the researchers. In this study, we address the problem of quantitatively modeling uncertainty in the accumulated GNSS and in wheel encoder data accumulated in anonymous urban environments, collected using vehicles. We also address the problem of utilizing that data in ego-motion estimation. There are seven factors that determine the magnitude of the uncertainty of a GNSS sensor. Because it is impossible to measure each of these factors, in this study, the uncertainty of the GNSS sensor is expressed through three variables, and the exact uncertainty is calculated. Using the proposed method, the uncertainty of the sensor is quantitatively modeled and robust localization is performed in a real environment. The approach is validated through experiments in urban environments.

Lower Bounds on DOP

2017 ◽  
Vol 70 (5) ◽  
pp. 1041-1061 ◽  
Author(s):  
Peter F. Swaszek ◽  
Richard J. Hartnett ◽  
Kelly C. Seals
Keyword(s):  
Lower Bounds ◽  
Global Navigation Satellite System ◽  
Satellite System ◽  
Navigation Satellite ◽  
Satellite Constellations ◽  
Dilution Of Precision ◽  
Gnss Positioning ◽  
Satellite Selection ◽  
Global Navigation ◽  
Global Navigation Satellite

Code phase Global Navigation Satellite System (GNSS) positioning performance is often described by the Geometric or Position Dilution of Precision (GDOP or PDOP), functions of the number of satellites employed in the solution and their geometry. This paper develops lower bounds to both metrics solely as functions of the number of satellites, effectively removing the added complexity caused by their locations in the sky, to allow users to assess how well their receivers are performing with respect to the best possible performance. Such bounds will be useful as receivers sub-select from the plethora of satellites available with multiple GNSS constellations. The bounds are initially developed for one constellation assuming that the satellites are at or above the horizon. Satellite constellations that essentially achieve the bounds are discussed, again with value toward the problem of satellite selection. The bounds are then extended to a non-zero mask angle and to multiple constellations.

scholarly journals Prospective directions for the development of microwave frequency standards for satellite navigation systems

2021 ◽  
Vol 2086 (1) ◽  
pp. 012073
Author(s):  
Ding Wang ◽  
V V Davydov ◽  
V Yu Rud
Keyword(s):  
Time Synchronization ◽  
Microwave Frequency ◽  
Global Navigation Satellite Systems ◽  
Navigation Satellite ◽  
Navigation Systems ◽  
Satellite Systems ◽  
Frequency Standards ◽  
Global Navigation ◽  
Satellite Navigation Systems ◽  
Global Navigation Satellite

Abstract The state of essential various quantum standards of GNSS frequencies for today are collected and presented, the results of analysis in the direction of modernization of time synchronization systems in global navigation satellite systems are presented. The most perspective directions of modernization of global navigation satellite systems are mentioned – the development of new atomic clocks on the mercury ions -199. The data on experimental satellite gives encouraging results.

scholarly journals Research on Vision System Calibration Method of Forestry Mobile Robots

2021 ◽  
Vol 14 ◽  
pp. 1107-1114
Author(s):  
Ruting Yao ◽  
Yili Zheng ◽  
Fengjun Chen ◽  
Jian Wu ◽  
Hui Wang
Keyword(s):  
Mobile Robots ◽  
Autonomous Navigation ◽  
Time Synchronization ◽  
Vision System ◽  
Robot Vision ◽  
Nonlinear Least Squares ◽  
Calibration Method ◽  
Time Operation ◽  
Spatial Calibration ◽  
Low Efficiency

Forestry mobile robots can effectively solve the problems of low efficiency and poor safety in the forestry operation process. To realize the autonomous navigation of forestry mobile robots, a vision system consisting of a monocular camera and two-dimensional LiDAR and its calibration method are investigated. First, the adaptive algorithm is used to synchronize the data captured by the two in time. Second, a calibration board with a convex checkerboard is designed for the spatial calibration of the devices. The nonlinear least squares algorithm is employed to solve and optimize the external parameters. The experimental results show that the time synchronization precision of this calibration method is 0.0082s, the communication rate is 23Hz, and the gradient tolerance of spatial calibration is 8.55e−07. The calibration results satisfy the requirements of real-time operation and accuracy of the forestry mobile robot vision system. Furthermore, the engineering applications of the vision system are discussed herein. This study lays the foundation for further forestry mobile robots research, which is relevant to intelligent forest machines.

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