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Zhang D.,State Key Laboratory of Astronautic Dynamics | Yu N.,PLA Second Artillery Engineering University
Proceedings - 2015 8th International Symposium on Computational Intelligence and Design, ISCID 2015 | Year: 2016

To cooperate different satellites in the complexity multi-satellite systems, this paper introduces the idea of self-assembly which is one of the basic mechanisms in the supramolecular chemistry. The multi-satellite systems is modeled by a half-edge graph model and its assembly growing method is proposed to automatically assemble resources for some mission. Finally, the simulation results of the resource assignment for the spaceflight mission by the proposed method show that the self-assembly method shed some light on the cooperation of multi-satellites. © 2015 IEEE.

Wang X.-H.,Tsinghua University | Wang X.-H.,State Key Laboratory of Astronautic Dynamics | Li J.-F.,Tsinghua University | Wang Y.-R.,State Key Laboratory of Astronautic Dynamics
Guangxue Jingmi Gongcheng/Optics and Precision Engineering | Year: 2013

As space-based cameras have advantages of lower energy consumption, higher accuracy, and easy to be miniaturized when they are used to observe space objects with middle or smaller sizes, this paper explores the orbit determination method and observability calculation method of space objects by space-based cameras. The advantages that the sun synchronous orbit is set as a space-based satellite orbit are analyzed and a space-based satellite orbit is designed by referencing several foreign space-based satellite orbits. Then the visible arc sections of space objects for different orbit types are simulated based on the space-based satellite orbit. According to the orbit measurement accuracy of existing space based optical observation equipment and errors of orbit dynamic model, the different system errors, random errors and dynamic model errors for the orbit measurements are added. Finally, the orbit determination precisions for space objects in different orbital altitudes are analyzed. Analysis results show that, for determining space target in low earth orbit with 6 of 7 minutes a day / two days of space-based optical measurement orbit data, the orbit determination precision is coincident with that of the United States of America cataloging (Two-line Elements, TLE) when the orbit measurement accuracy is better than 30″ and the dynamic model error is less than 50%. Moreover, for determining space target in earth synchronous orbit with 10 min / day of space-based optical measurement orbit data, the orbit determination precision is in the orbit accuracy range of the United States of America cataloging when the orbit measurement accuracy is better than 10″ and the dynamic model error is less than 50%.

Chen Q.,National University of Defense Technology | Kuang G.,National University of Defense Technology | Li J.,Xiamen University | Sui L.,State Key Laboratory of Astronautic Dynamics | Li D.,93502 Unit
IEEE Transactions on Geoscience and Remote Sensing | Year: 2013

This paper presents a new unsupervised land cover/land use classification scheme using polarimetric synthetic aperture radar (PolSAR) imagery based on polarimetric scattering similarity. Compared with the H/alpha classification scheme based on a dominant 'average' scattering mechanism, the proposed scheme has such advantages as the following: 1) The major scattering mechanism represents a target scattering in the low-entropy case; 2) it also represents both the major and minor scattering mechanisms in the medium-entropy case; and 3) all the scattering mechanisms in the high-entropy case can be represented. The major and minor scattering mechanisms have been identified automatically based on the relative magnitude of multiple-scattering similarities. The canonical scattering corresponding to maximum scattering similarity is regarded as the major scattering mechanism. The result obtained using the National Aeronautics and Space Administration/Jet Propulsion Laboratory's AIRSAR L-band PolSAR imagery reveals that the proposed scheme is more effective as compared to the existing models and promises to increase the accuracy of the classification and interpretation. Copyright © 1980-2012 IEEE.

Yu J.H.,University of Chinese Academy of Sciences | Yu J.H.,CAS Wuhan Institute of Geodesy and Geophysics | Yu J.H.,State Key Laboratory of Astronautic Dynamics | Zhao D.M.,Zhengzhou Institute of Surveying and Mapping
Science China Earth Sciences | Year: 2010

Here we report new approaches of recovering the Earth gravitational field from GOCE (Gravity field and steady-state Ocean Circulation Explorer) gradiometric data with the help of the gradient tensor's invariants. Our results only depend on GOCE satellite's position and gradiometry, in other words, they are completely independent of the satellite attitude. First, starting from the invariants, linearization models are established, which can be referred as the general boundary conditions on the satellite's orbit. Then, the spherical approximation expressions for the models are derived, and the corresponding solving methods for them are discussed. Furthermore, considering effects of J2-term, the spherical approximation models are improved so that the accuracies of the boundary conditions can be theoretically raised to O(J2 2· T), which is approximately equivalent to O(T2). Finally, some arithmetic examples are constructed from EGM96 model based on the derived theories, and the computational results illustrate that the spherical models have accuracies of 10-7 and the order recovering the gravitational field can reach up to 200, and the models with regard to effect of J2-term have accuracies of 10-8 and the order can reach up to 280. © 2010 Science China Press and Springer-Verlag Berlin Heidelberg.

Luo Y.,National University of Defense Technology | Yang Z.,National University of Defense Technology | Li H.,State Key Laboratory of Astronautic Dynamics
Science China: Physics, Mechanics and Astronomy | Year: 2014

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. © 2014 Science China Press and Springer-Verlag Berlin Heidelberg.

Gao Y.,State Key Laboratory of Astronautic Dynamics | Gao Y.,Chinese Academy of Sciences | Li H.-N.,State Key Laboratory of Astronautic Dynamics | He S.-M.,Chinese Academy of Sciences
Acta Mechanica Sinica/Lixue Xuebao | Year: 2012

Chang'e-2, Chinese second lunar probe, was inserted into a 100 km altitude low lunar orbit on October 9th, 2010, its purpose is to continuously photograph the lunar surface and possibly chosen landing sites for future lunar missions. The probe will still carry considerable amount of propellant after completing all prescribed tasks in about six months. After the successful launch of Chang'e-2, we began designing the probe's subsequent flight scenario, considering a total impulse of 1 100 m/s for takeoff from low lunar orbit and a maximum 3×106 km distance for Earth-probe telecommunication. Our first-round effort proposed a preliminary flight scenario that involves consecutive arrivals at the halo orbits around the Earth-Moon L1/L2 and Sun-Earth L1/L2 points, near-Earth asteroid flyby, Earth return, and lunar impact. The designed solution of Chang'e-2's subsequent flight scenario is a multi-segment flight trajectory that serves as a reference for making the final decision on Chang'e-2's extended mission, which is a flight to the Sun-Earth L2 point, and a possible scheme of lunar impact via Earth flyby after remaining at the Sun-Earth L2 point was also presented. The proposed flight trajectory, which possesses acceptable solution accuracy for mission analysis, is a novel design that effectively exploits the invariant manifolds in the circular restricted three-body problem and the patched-manifold-conic method. © The Chinese Society of Theoretical and Applied Mechanics and Springer-Verlag Berlin Heidelberg 2012.

Bai L.,Xidian University | Su X.,Xidian University | Zhou W.,Xidian University | Ou X.,State Key Laboratory of Astronautic Dynamics
Review of Scientific Instruments | Year: 2015

For the precise phase difference measurement, this paper develops an improved dual phase coincidence detection method. The measurement resolution of the digital phase coincidence detection circuits is always limited, for example, only at the nanosecond level. This paper reveals a new way to improve the phase difference measurement precision by using the border stability of the circuit detection fuzzy areas. When a common oscillator signal is used to detect the phase coincidence with the two comparison signals, there will be two detection fuzzy areas for the reason of finite detection resolution surrounding the strict phase coincidence. Border stability of fuzzy areas and the fluctuation difference of the two fuzzy areas can be even finer than the picoseconds level. It is shown that the system resolution obtained only depends on the stability of the circuit measurement resolution which is much better than the measurement device resolution itself. © 2015 AIP Publishing LLC.

Xi T.,State Key Laboratory of Astronautic Dynamics | Li J.C.,State Key Laboratory of Astronautic Dynamics | Pan W.Q.,State Key Laboratory of Astronautic Dynamics
Applied Mechanics and Materials | Year: 2013

Spacecraft proximity formation flying is essential for future autonomous space mission such as autonomous rendezvous and docking and assembly of space system on-orbit. In order to improve the autonomy of relative motion control between two spacecrafts and concerning the effect of perturbation by bounded uncertain disturbance, a novel nonlinear adaptive feedback controller is developed based on sliding mode control law to maintain the desired reference trajectory as precisely as possible. The simulation results demonstrate the control scheme can effectively carry out the relative motion maintenance and have better asymptotically stability. © (2013) Trans Tech Publications, Switzerland.

Gao Y.,State Key Laboratory of Astronautic Dynamics | Gao Y.,Chinese Academy of Sciences
Acta Mechanica Sinica/Lixue Xuebao | Year: 2013

Driven by curiosity about possible flight options for the Chang'e-2 spacecraft after it remains at the Sun-Earth L2 point, effective approaches were developed for designing preliminary fuel-optimal near-Earth asteroid flyby trajectories. The approaches include the use of modified unstable manifolds, grid search of the manifolds' parameters, and a two-impulse maneuver for orbital phase matching and z-axis bias change, and are demonstrated to be effective in asteroid target screening and trajectory optimization. Asteroid flybys are expected to be within a distance of 2 × 107 km from the Earth owing to the constrained Earth-spacecraft communication range. In this case, the spacecraft's orbital motion is significantly affected by the gravities of both the Sun and the Earth, and therefore, the concept of the "heliocentric oscillating-Kepler orbit" is proposed, because the classical orbital elements of the flyby trajectories referenced in the heliocentric inertial frame oscillate significantly with respect to time. The analysis and results presented in this study show that, among the asteroids whose orbits are the most accurately predicted, "Toutatis", "2005 NZ6", or "2010 CL19" might be encountered by Chang'e-2 in late 2012 or 2013 with total impulses less than 100m/s. © 2013 The Chinese Society of Theoretical and Applied Mechanics; Institute of Mechanics, Chinese Academy of Sciences and Springer-Verlag Berlin Heidelberg.

Wei P.-B.,Xidian University | Zhang M.,Xidian University | Niu W.,State Key Laboratory of Astronautic Dynamics | Jiang W.-Q.,Xidian University
IEEE Transactions on Antennas and Propagation | Year: 2012

In the radar cross section (RCS) prediction of complex target, the intensive computational burden occurs while calculating the multiple scattering effect. In order to overcome the large computing, we present the program executing on graphics processing units (GPUs). In this paper, we analyze the scattering properties of the satellite, on which the antennas are described as cubes and columns, by employing the GPU-based combinational method of geometrical optics (GO) and physical optics (PO) together with the kd-tree technique. Furthermore, due to this distinctive treatment, the improved method yields a superior performance at high frequency. Some examples will be displayed in the following text. The agreement of the results yielded in this paper with the experimental and other exact results demonstrates the accuracy and efficiency of this useful technique. © 2012 IEEE.

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