BeiDou Regional Navigation Satellite System Completed

As the 16th BeiDou navigation satellite was successfully launched into space at 23:33 Beijing Time from the Xichang Satellite Launch Center (XSLC) on October 25, 2012, China completed the construction of the BeiDou Regional Navigation Satellite System that starts to officially provide services for most parts of the Asia-Pacific region from December 27. The 16th BeiDou navigation satellite, the last one for the regional BeiDou system, was developed by China Academy of Space Technology under CASC.

Formation Configuration Design for Low-Earth Orbit Regional Navigation Satellites

In the event of a significant natural disaster or a local conflict,the demand for a regional satellite navigation becomes imperative.The navigation can provide accurate position information and navigation augmentation services for regional emergency operations.To satisfy the requirements,a formation configuration of low-Earth orbit(LEO)regional navigation satellites is proposed innovatively.The strategy offly-around formation consisting of four satellites for LEO regional navigation is determined and a comprehensive configuration design method for the formation is presented,encompassing the determination of configuration parameters,the establishment of dynamic equations and the presentation of performance indicators,including duration of ground coverage,positioning accuracy Geometric Dilution Precision(GDOP)and fuel consumption.The effects of formation radius and orbit altitude on the performance indicators are analyzed,respectively.Based on the above investigations,a method to enhance regional navigation performances by using genetic algorithm(GA)guided by penalty function is introduced.The rationality and feasibility of the formation configuration are verified through simulation studies.

Integrated constellation design and deployment method for a regional augmented navigation satellite system using piggyback launches

The method proposed in this paper is adopted to solve problem B of the 9th China Trajectory Optimization Competition(CTOC).An accurate and economical constellation design strategy for regional augmented navigation satellite systems(RANSSs)has attracted a substantial amount of research interest owing to the increased demand for navigation services in complex environments.This paper proposes a hybrid method of constellation design and deployment for a RANSS to satisfy the navigation performance requirements and minimize the construction cost.First,the search spaces of the design parameters are determined by analyzing the orbital parameters of piggyback launches.Second,the constellation is designed as a combined Walker constellation and optimized by a differential evolution(DE)algorithm.Finally,optimal strategies for deploying satellites to the desired orbits are obtained using a transfer optimization design.The method was adopted to design a RANSS for servicing the 182 cities in the Asia-Pacific region.The configuration consists of five orbital planes and 80 navigation satellites and achieves a low construction cost with 10 piggyback launches.Furthermore,the constellation can cooperate with an existing navigation satellite system to further improve the navigation accuracy for all cities.The results reveal that the RANSS design and deployment problem can be effectively solved with a low construction cost and high navigation performance.

Comparison of availability and reliability among different combined-GNSS/RNSS precise point positioning

With emergence of the BeiDou Navigation Satellite System(BDS), the Galileo Satellite Navigation System(Galileo), the Quasi-Zenith Satellite System(QZSS)and the restoration of the Global Navigation Satellite System(GLONASS), the single Global Positioning System(GPS) has been gradually expanded into multiple global and regional navigation satellite systems(multi-GNSS/RNSS). In view of differences in these 5 systems, a consolidated multi-GNSS/RNSS precise point positioning(PPP) observation model is deduced in this contribution. In addition, the performance evaluation of PPP for multi-GNSS/RNSS is conducted using a large number of the multi-GNSS experiment(MGEX) station datasets. Experimental results show that multi-GNSS/RNSS can guarantee plenty of visible satellites effectively. Compared with single-system GPS, PDOP, HDOP, and VDOP values of the multi-GNSS/RNSS are improved by 46.8%, 46.5% and 46.3%, respectively. As for convergence time, the static and kinematic PPP of multi-GNSS/RNSS are superior to that of the single-system GPS, whose reliability, availability, and stability drop sharply with the increasing elevation cutoff. At satellite elevation cutoff of 40 °, the single-system GPS fails to carry out continuous positioning because of the insufficient visible satellites, while the multi-GNSS/RNSS PPP can still get positioning solutions with relatively high accuracy, especially in the horizontal direction.

Performance evaluation method of hybrid navigation constellations with invalid satellites

The construction of a navigation system plays an important role in the development of national politics,economy and military affairs.Nowadays,the Beidou navigation system is facing a transition period from the regional navigation system to the global one.For the global constellation,the system performance will not be seriously degraded when one or two satellites are invalid,but it is out of case for the regional constellation,which usually has fewer satellites and less redundancy.This paper deals with this problem of hybrid constellations and analyzes the influence of the disabled satellites on the system.With hybrid constellations and simulation methods designed,the influence of invalid satellites on the navigation system is fully investigated.

Ideal proportional navigation for exoatmospheric interception

Ideal proportional navigation （IPN） is a natural choice for exoatmospheric interception for its mighty capture capability and ease of implementation. The closed-form solution of two- dimensional ideal proportional navigation was conducted in previous public literature, whereas the practical interception happens in the three-dimensional space. A novel set of relative dynamic equations is adopted in this paper, which is with the advantage of decoupling relative motion in the instantaneous rotation plane of the line of sight from the rotation of this plane. The dimension-reduced IPN is constructed in this instantaneous plane, which functions as a three-dimensional guidance law. The trajectory features of dimension-reduced IPN are explored, and the capture regions of dimension-reduced IPN with limited acceleration against nonmaneuvering and maneuvering targets are analyzed by using phase plane method. It is proved that the capture capability of IPN is much stronger than true proportional navigation （TPN）, no matter the target maneuvers or not. Finally, simulation results indicate that IPN is more effective than TPN in exoatmospheric interception scenarios.