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The exploration of satellite clock and ephemeris error correction in wide area differential system

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The exploration of satellite clock and ephemeris error corre...

Direct Optimization of Low-thrust Many-revolution Earth-orbit Transfers

第三届中国卫星导航学术年会

作者： ChengLin CAI 1* XiaoHui LI 2 &HaiTao WU 3 1.Guilin University of Electronic Technology,541004,Guilin,china 2.National Time Service Center,chinese academy of sciences,710600,Lintong,china 3.academy of opto-electronics,chinese academy of sciences,100094,beijing,china

Real time principle of wide area differential GPS(WADGPS)uses a generally inverted positioning method of four-dimensional solution of satellite clock and ephemeris *** with the real time single point positioning,positioning accuracy of this method is improved greatly,but the DOP of four-dimensional calculation is up to several hundred,under the error amplification effect of DOP,1 m positioning precision level of WADGPS is difficult to *** overcome the limit of DOP,the feasibility on large and small part decomposition of satellite clock and ephemeris error is analyzed, and optimal differential performances of the exploring two smallness correction methods:Small DOP and no DOP constraint,are analyzed,and they will be the foundation for further exploration.

关键词： wide area differential GPS(WADGPS) DOP satellite clock ephemeris

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chinese Journal of Aeronautics 2009年第4期22卷 426-433页

作者： Gao Yang academy of opto-electronics,chinese academy of sciences,beijing 100190,china academy of opto-electronics Chinese Academy of Sciences Beijing 100190 China

Low-thrust Earth-orbit transfers with 10^- 5-order thrust-to-weight ratios involve a large number of orbital revolutions which poses a real challenge to trajectory optimization. This article develops a direct method to optimize minimum-time low-thrust many-revolution Earth-orbit transfers. A parameterized control law in each orbit, in the form of the true optimal control, is proposed, and the time history of the parameters governing the control law is interpolated through a finite number of nodal values. The orbital averaging method is used to significantly reduce the computational workload and the trajectory optimization is conducted based on the orbital averaging dynamics expressed by nonsingular equinoctial elements. Furthermore, Earth＇s shadowing and perturbation effects are taken into account. The optimal transfer problem is thus converted to the parameter optimization problem that can be solved by nonlinear programming. Taking advantage of the mapping between the parameterized control law and the Lyapunov control law, a technique is proposed to acquire good initial guesses for optimization variables, which results in enlarged convergence domain of the direct optimization method. Numerical examples of optimal Earth-orbit transfers are presented.

关键词： low thrust orbital transfer optimization direct method orbital averaging Lyapunov method

The solid lubricating material experiment device for Shenzhou-7 Spaceship

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Science china(Technological sciences) 2010年第9期53卷 2521-2527页

作者： WANG Ke1,2,REN WeiJia1,WANG ShiDa1 & WENG LiJun3 1 academy of opto-electronics,chinese academy of sciences,beijing 100190,china 2 Graduate University of chinese academy of sciences,beijing 100049,china 3 Lanzhou Institute of Chemical Physics,chinese academy of sciences,Lanzhou 730000,china academy of opto-electronics Chinese Academy of Sciences Graduate University of chinese academy of sciences

A solid lubricating material exposure experiment in space is one of the missions during the seventh manned spaceflight of china,and the key is to develop a device which can be fixed reliably outside of the orbital module and can be fetched conveniently by an astronaut during space *** solid lubricating material experiment device needs to be locked reliably in a vibrating and impacting environment during the launch phase,and should meet the requirement that it can be unlocked and fetched reliably by the astronaut wearing an extravehicular spacesuit via simple operations in orbit in an environment of high and low *** for the device we developed,the environmental characteristic of the mission was analyzed,the mechanical analysis and thermal analysis were carried out,and then a mechanism with functions of mechanical locking,structural self-locking and manual unlocking was *** device was verified by a sequence of experiments and was fetched by the astronaut during the flight of the Shenzhou-7 Spaceship.

关键词： manned spaceflight exposure experiment mechanism unlock

ON DISCRETE PROJECTION AND NUMERICAL BOUNDARY CONDITIONS FOR THE NUMERICAL SOLUTION OF THE UNSTEADY INCOMPRESSIBLE NAVIER-STOKESEQUATIONS

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Journal of Computational Mathematics 2002年第1期20卷 35-56页

作者： Lan Chieh Huang (ICMSEC, academy of Mathematics and System sciences, chinese academy of sciences, beijing 100080, china) ICMSEC Academy of Mathematics and System Sciences Chinese Academy of Sciences 北京 100080

Focuses on a study on the fully implicit Crank Nicholson (CN) schemes and three projection methods for approximate preservation of component-consistency under projection. Transformation from incompressible Navier-Stokes equations to differential algebraic equations CN schemes; Local errors of CN projection methods; Numerical boundary conditions.

关键词： differential algebraic equations discrete projection numerical boundary conditions

Research on applying physical chaos generator to spacecraft information security

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Science china(Technological sciences) 2009年第5期52卷 1463-1470页

作者： ZHAO HePing State Key Laboratory of Information Security,Graduate University of chinese academy of sciences,beijing 100049,china china academy of Space Technology,beijing 100094,china State Key Laboratory of Information Security Graduate University of Chinese Academy of Sciences china academy of Space Technology

The effectiveness of a short-length message extension method based on physical chaos generator was analyzed and the entropy of the extended message was calculated in this *** analysis demon-strated that with the mentioned method the entropy of short-length messages,which are repeatedly used in spacecraft data systems,is obviously increased,and the security of transmission is enhanced as *** paper also presented an improvement of the protocol for secret key agreement presented by *** and *** of depending on characteristics of communication channel,this method takes advantage of the random data produced by physical chaos generator to preset the initial parameters of the procedure on both sides of communication,so that the procedure and quantity of cipher key can be precisely *** method can be used to cipher key management of se-cure communication between long life-span spacecraft and ground system.

关键词： physical chaos generator spacecraft information security message extension cipher key management

THE DUAL MIXED METHOD FOR AN UNILATERAL PROBLEM

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Journal of Computational Mathematics 2003年第6期21卷 733-746页

作者： Lie-heng Wang(LSEC, ICMSEC, academy of Mathematics and System sciences, chinese academy of sciences,beijing 100080, china) LSEC ICMSEC Academy of Mathematics and System Sciences Chinese Academy of Sciences Beijing 100080 China

In this paper, the dual mixed method for an unilateral problem, which is the simplified modelling of scalar function for the friction-free contact problem, is considered. The dual mixed problem is introduced, the existence and uniqeness of the solution of the problem are presented, and error bounds O(h3/4) and O(h3/2) are obtained for the dual mixed finite element approximations of Raviart-Thomas elements for k = 0 and k = 1 respectively.

关键词： Dual Mixed Method Unilateral Problem.

COMPOSITE-STEP LIKE FILTER METHODS FOR EQUALITY CONSTRAINT PROBLEMS

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Journal of Computational Mathematics 2003年第5期21卷 613-624页

作者： Pu-yan Nie(LSEC, ICMSEC, academy of Mathematics and System sciences, chinese academy of sciences, beijing 100080, china) 中科院数学与系统科学院 LSEC ICMSEC CAS 北京 100080

In a composite-step approach, a step Sk is computed as the sum of two components Uk and hk. The normal component Vk, which is called the vertical step, aims to improve the linearized feasibility, while the tangential component hk, which is also called horizontal step, concentrates on reducing a model of the merit functions. As a filter method, it reduces both the infeasibility and the objective function. This is the same property of these two methods. In this paper, one concerns the composite-step like filter approach. That is, a step is tangential component hk if the infeasibility is reduced. Or else, Sk is a composite step composed of normal component Uk, and tangential component hk.

关键词： Composite-step like approaches Filter methods Equality constraints Sequen- tial quadratic programming(SQP) algorithms Normal component Tangential component Convergence.

A CLASS OF NEW PARALLEL HYBRID ALGEBRAIC MULTILEVEL ITERATIONS

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Journal of Computational Mathematics 2001年第6期19卷 651-672页

作者： Zhong-zhi Bai (LSEC ICMSEC, academy of Mathematics and Systems sciences, chinese academy of sciences, beijing 100080, china) 中科院计算数学与科学工程计算所北京 100080

Presents preconditioning matrices having parallel computing function for the coefficient matrix and a class of parallel hybrid algebraic multilevel iteration methods for solving linear equations. Solution to elliptic ... 详细信息

关键词： elliptic boundary value problem system of linear equations symmetric positive definite matrix multilevel iteration parallel method

CONVERGENCE OF NONLINEAR CONJUGATE GRADIENT METHODS

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Journal of Computational Mathematics 2001年第5期19卷 539-548页

作者： Yu-hong Dai (LSEC, ICMSEC, academy of Mathematics and Systems sciences, chinese academy of sciences,beijing 100080, china) 中科院计算数学与科学工程计算所北京 100080

Presents a study on methods for unconstrained optimization. Assumptions of the study; Main results; Convergence properties of the methods under simplified Armijo-type line search.

关键词： unconstrained optimization conjugate gradient (generalized) line search global convergence