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| 1 | A novel satellite-equipped receiver for autonomous monitoring of GNSS navigation signal quality显示文摘Global navigation satellite system(GNSS) comes with potential unavoidable application risks such as the sudden distortion or failure of navigation signals because its satellites are generally operated until failure. In order to solve the problems associated with these risks, receiver autonomous integrity monitoring(RAIM) and ground-based signal quality monitoring stations are widely used. Although these technologies can protect the user from the risks, they are expensive and have limited region coverage. Autonomous monitoring of satellite signal quality is an effective method to eliminate these shortcomings of the RAIM and ground-based signal quality monitoring stations; thus, a new navigation signal quality monitoring receiver which can be equipped on the satellite platform of GNSS is proposed in this paper. Because this satellite-equipped receiver is tightly coupled with navigation payload, the system architecture and its preliminary design procedure are first introduced. In theory, code-tracking loop is able to provide accurate time delay estimation of received signals. However, because of the nonlinear characteristics of the navigation payload, the traditional code-tracking loop introduces errors. To eliminate these errors, the dummy massive parallel correlators(DMPC) technique is proposed. This technique can reconstruct the cross correlation function of a navigation signal with a high code phase resolution. Combining the DMPC and direct radio frequency(RF) sampling technology, the satellite-equipped receiver can calibrate the differential code bias(DCB) accurately. In the meantime, the abnormities and failures of navigation signal can also be monitored. Finally, the accuracy of DCB calibration and the performance of fault monitoring have been verified by practical test data and numerical simulation data, respectively. The results show that the accuracy of DCB calibration is less than 0.1 ns and the novel satellite-equipped receiver can monitor the signal quality effectively. | YANG Jian YANG YiKang LI Ji Sheng LI HengNian YANG TianShe | 2016 | Science China(Technological Sciences)2016，59，7： | 6 |
| 2 | Mathematical prototypes for collocating geostationary satellites显示文摘Collocating geostationary satellites sharing the same position is much demanded for satellite operation recently,the separation strategies are adopted to safeguard the satellites collocated of leaving the relative distance beyond collision with different sets of orbit parameters.This paper presents the mathematical prototypes which establish the allowable relative distance with uncertainty of orbital determination(OD),as well as the orbital element offset for each pair of collocated satellites,and puts forward algorithms to build such relationship to face the challenge of putting three satellites sharing the same position,the algorithms to allocate the longitude,eccentricity and inclination for each satellite are also given to ascertain that the mathematical prototypes are the guide specification to design collocation strategy for geostationary satellites. | LI HengNian GAO ZhaoZhao LI JiSheng LI QuanJun XUE Dan LI DongLin | 2013 | Science China(Technological Sciences)2013，56，5： | 6 |
| 3 | Design and optimization of low-energy transfer orbit to Mars with multi-body environment显示文摘This paper discusses the problem of design and optimization of low-energy transfer orbit with multi-body environment. A new integrative method is proposed to effectively solve the problem, in which the parameterized patched manifolds in CR3BP(circular restricted three-body problems), the shape-based method with multi-body environment, the homotopic method with multi-body environment, and the low-thrust capturing and descending algorithm with multi-body environment are all included. Firstly, the parameters describing the patched manifolds in CR3 BP are optimized until the least total absolute velocity increment has been got, including the employment of the shape-based method with multi-body environment. Secondly, the low-thrust control laws of the transfer orbit are optimized employing the homotopic method with multi-body environment that transfers the fuel optimization problem to an easier energy optimization problem. Thirdly, the low-thrust descending orbit around Mars is computed using the laws proposed in this paper. As a typical example, the Earth-Mars transfer orbit design is discussed. The results showed that the parameters describing the patched manifolds could be optimized by the DE(differential evolution) algorithm effectively; the homotopic method with multi-body environment could get the optimal value that meets the first order optimality conditions; and the low-thrust descending orbit could effectively be captured by Mars and finally become a circular parking orbit around it by the hypothesis control laws proposed in this paper. It shows that the final fuel cost is much less than the optimal transfer in the patched two-body problems. In conclusion, the method proposed in this paper could effectively solve the low-energy low-thrust optimal control problem in multi-body environment for the future deep space explorations. | LU Yi LI HengNian LI JiSheng CHE Zheng YANG YiKang YANG Yuan SUN Yang | 2015 | Science China(Technological Sciences)2015，58，10： | 3 |
| 4 | Robust optimization of nonlinear impulsive rendezvous with uncertainty显示文摘The optimal rendezvous trajectory designs in many current research efforts do not incorporate the practical uncertainties into the closed loop of the design.A robust optimization design method for a nonlinear rendezvous trajectory with uncertainty is proposed in this paper.One performance index related to the variances of the terminal state error is termed the robustness performance index,and a two-objective optimization model(including the minimum characteristic velocity and the minimum robustness performance index)is formulated on the basis of the Lambert algorithm.A multi-objective,non-dominated sorting genetic algorithm is employed to obtain the Pareto optimal solution set.It is shown that the proposed approach can be used to quickly obtain several inherent principles of the rendezvous trajectory by taking practical errors into account.Furthermore,this approach can identify the most preferable design space in which a specific solution for the actual application of the rendezvous control should be chosen. | LUO YaZhong YANG Zhen LI HengNian | 2014 | Science China(Physics,Mechanics & Astronomy)2014，57，4： | 2 |
| 5 | Detection of objects underneath the water-sediment interface based on time reversal processing显示文摘用与传播和接收的相互作用集中的时间颠倒的技术在高度回响的环境检测一个目标的存在和缺席的假设测试被学习。与传播和接收的相互作用集中的时间颠倒(TR ) 如下:PS (探查来源) 在对象附近被定位产生信号, SRA (来源接收装置数组) 收到 PS 播送的信号并且由物理 TR 集中在对象的地点集中信号(即,有补偿的多路径的反的 beamforming ) 。TR 传播数组和接收数组交互地集中与算法的 TR 集中由目标散布的回响(即,有补偿的多路径的 beamforming ).Meanwhile 常规 BS (舷侧) 传播察觉和 TR 察觉被比较。实验在实验室波导被进行证明理论分析和结果。因而 TR 察觉得到更多比常规 BS 传播察觉逼近 echo-to-reverberation 比率。 | YAN Liming LI Jianlong PAN Xiang ZHAO Hangfang ZHU Hengnian | 2009 | Chinese Journal of Acoustics2009，28，4： | 1 |
| 6 | Stable periodic orbits for spacecraft around minor celestial bodies显示文摘We are interested in stable periodic orbits for spacecraft in the gravitational eld of minor celestial bodies.The stable periodic orbits around minor celestial bodies are useful not only for the mission design of the deep space exploration,but also for studying the long-time stability of small satellites in the large-size-ratio binary asteroids.The irregular shapes and gravitational elds of the minor celestial bodies are modeled by the polyhedral model.Using the topological classi cations of periodic orbits and the grid search method,the stable periodic orbits can be calculated and the topological cases can be determined.Furthermore,we nd ve di erent types of stable periodic orbits around minor celestial bodies:(1)stable periodic orbits generated from the stable equilibrium points outside the minor celestial body;(2)stable periodic orbits continued from the unstable periodic orbits around the unstable equilibrium points;(3)retrograde and nearly circular periodic orbits with zero-inclination around minor celestial bodies;(4)resonance periodic orbits;(5)near-surface inclined periodic orbits.We take asteroids 243 Ida,433 Eros,6489 Golevka,101955 Bennu,and the comet 1P/Halley for examples. | Yu Jiang Jurgen Arno Schmidt Hengnian Li Xiaodong Liu Yue Yang | 2018 | Astrodynamics2018，2，1： | 1 |
| 7 | Analysis of noncommensurate sampling effects on the performance of PN code tracking loops显示文摘Noncoherent early-late processing(NELP) code tracking loops are often implemented using digital hardware for digital global positioning system(GPS) receivers. Noncommensurate sampling technology is widely used because it is viewed as an effective solution to cope with the drawback of digital effects. However, the relationship between the sampling rate and auto-correlation function(ACF) is not adequately characterized by traditional analysis. The principles for selecting the sampling rate are still not apparent. In order to solve this problem, we first analyzed the effects of different sampling rates on ACF and obtained the analytical form of a discrete auto-correlation function(DACF) for a noncommensurate sampling rate. Based on the result, the relationship between the step variation in DACF and NELP parameters such as sampling rate, integration time, and correlator spacing was determined. The maximum step variation size of DACF was also determined. However, considering the actual situation, additional factors such as code Doppler shift, precorrelation filter, and thermal noise may degrade the step variation of DACF. The relationship between the step variation and these factors was analyzed separately. An appropriate sampling rate and appropriate correlator spacing were proposed to achieve the typical accuracy of measurement. The numerical simulation verified the validity of the above theoretical analyses, and finally, the conclusions and design constraints for the digital GPS receiver are summarized. | YANG Jian YANG YiKang LI JiSheng LI HengNian YANG TianShe | 2018 | Science China(Technological Sciences)2018，61，6： | 1 |
| 8 | Determining origins of satellite breakup events in LEO region显示文摘Currently,a surge in the number of spacecraft and fragments is observed,leading to more frequent breakup events in low Earth orbits(LEOs).The causes of these events are being identified,and specific triggers,such as collisions or explosions,are being examined for their importance to space traffic management.Backward propagation methods were employed to trace the origins of these types of breakup events.Simulations were conducted using the NASA standard breakup model,and satellite Hitomi’s breakup was analyzed.Kullback-Leibler(KL)divergences,Euclidean 2-norms,and Jensen-Shannon(JS)divergences were computed to deduce potential types of breakups and the associated fragmentation masses.In the simulated case,a discrepancy of 22.12 s between the estimated and actual time was noted.Additionally,the breakup of the Hitomi satellite was estimated to have occurred around UTC 1:49:26.4 on March 26,2016.This contrasts with the epoch provided by the Joint Space Operation Center,which was estimated to be at 1:42 UTC±11 min.From the findings,it was suggested that the techniques introduced in the study can be effectively used to trace the origins of short-term breakup events and to deduce the types of collisions and fragmentation masses under certain conditions. | Yongjie Liu Yu Jiang Hengnian Li Zongbo Huyan Hongchao Wang | 2023 | Astrodynamics2023，7，4： | 0 |
| 9 | Analytical Propagation of Space Debris Density for Collisions near Sun-Synchronous Orbits显示文摘The increasing frequency of human launches has led to a dramatic increase in the amount of space debris,especially near sunsynchronous orbits.Most of the fragments are small in size,which may make tracking difficult.Therefore,characterizing the distribution,evolution,and collision risk of small debris has long been a difficult issue.This paper is aimed at investigating the orbital evolution and global dispersion behavior of debris clouds near sun-synchronous orbits.Firstly,the NASA breakup model is used to provide an initial distribution of small fragments after collision events.Secondly,the continuity equation is adopted to propagate the density variation analytically.Furthermore,we introduce some statistical quantities and the entropy of debris clouds to model the randomness and band formation.A theorem concerning the equivalence of the band formation and maximal entropy is presented.The accuracy of the band formation time estimation is also discussed.For noncatastrophic collisions at an altitude of 800 km due to a projectile with a mass of 100 g and a collision velocity of 1 km/s,we compare the analytical and numerical results of space debris density.The results show that the maximal peak error is within 0.17,and the mean square error is about 0.25 at 400 days.Additionally,the entropy of right ascension of the ascending node is 8.5%less than that for debris clouds near an orbit with the same altitude and an inclination of 30 deg.This indicates the concentrating behavior for debris clouds near sun-synchronous orbits. | Yongjie Liu Yu Jiang Hengnian Li | 2022 | Space(Science & Technology)2022，，1： | 0 |
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