Abstract： On an ultraquiet platform, the vibration of flexible payloads will decrease the onorbit identification accuracy of platform model parameters. Based on the multiple concurrent recursive least square method (MCRLS)，a parameter identification method is proposed, which improves the onorbit identification accuracy of the parameters of ultraquiet platform and provides precise dynamic models. The ultraquiet platform dynamic model is established with the flexible payload vibration. The Kalman Filter is used to estimate the vibration mode of the flexible payload. The parameters of the dynamic model are identified via recursive least square method. Simulation results show that, the estimation precision of ultraquiet platform model parameters is improved with the proposed method, compared with the one without consideration of  the vibration of flexible payloads.

Abstract： A multivariable frequency domain stability analysis method is proposed in this paper for multistage compound control systems in satellites with multistage drive mechanisms. Firstly, a satellite integrated linear model with multistage drive mechanism is established based on the model simplification. A singlechannel output linear feedback controller is designed for the attitude control system. Using the transfer function matrix fractional description, the polynomial matrix transformation is used to obtain the pole distribution of multichannel closedloop systems. The stability conditions of multivariable frequency domain input and output of the closedloop system are determined. The example and simulation results show that this method can verify the stability of closedloop satellite system with multistage drive mechanism and provide an effective tool for controller parameter design.

Abstract： An airtoair missile trajectory optimization problem is discussed in the case of overthe shoulder. The scheme takes the angle of attack constraints into consideration. A virtualtargetbased guidance law is designed for large offboresight launching of airtoair missile. After studying the results of the optimal trajectory, which is solved by gauss pseudospectral method（GPM）, a threesegment guidance command is proposed. The differences in command due to flight height, flight velocity and the position of virtual target are studied. Meanwhile, the robustness of the guidance law is improved via correcting it online. Simulation results indicate that the proposed command can make the missile turn rapidly with body axis pointing toward virtual target after turning.

Abstract： The classIXV aircraft is a lifting body without wings, and is actuated through the combination of two body flaps mounted at the aft windward side of the vehicles and RCS thrusters. The accurate reentry guidance and attitude control approaches are studied in this paper. Firstly, a numerical predictorcorrector guidance law with flight path constraints is designed to enhance the robustness and accuracy of guidance system. Secondly, a hybrid control law is proposed, with the yaw axis performed by the RCS thrusters, and both the longitudinal and lateral axes performed by the RCS and aerodynamic flaps. Furthermore, robust servo LQR method is used to design the control parameters rapidly. Finally, Monte Carlo simulation is presented to validate the high accuracy and robustness of the proposed algorithm.

Abstract： The entry flight envelope of orbital reentry vehicle is divided into three phases: the atmospheric entry, terminal area energy management (TAEM) and autolanding. In this paper, a flight range and vertical profile optimization algorithm are developed for the terminal area energy management phase. Through the propagation of the dynamic equation from different initial states, by maximizing the control margin of speed brake, a range which is most fit for the aerodynamic characteristic of the vehicle is generated, and the best heightdynamic profile in correspondence with this range is designed simultaneously. The 6DOF simulations under various initial states deviation and dynamic uncertainties demonstrate that the vertical profile is robust.

Abstract： Focusing on the problems of computational burden and shortage of storage space for visual navigation in extraterrestrial body landing missions, a sparse descriptor for landmarks is proposed in this paper. The scale prediction and scale transformation of descent images are introduced, and the image features are extracted based on Harris algorithm, and FREAK algorithm is improved to descript the image features. Finally, the performances of the proposed algorithm, FREAK algorithm and SURF algorithm are compared under four external disturbances. The simulation results show that the proposed algorithm greatly reduces computational burden and demand for storage space, and is more suitable for landing missions of extraterrestrial objects.

Abstract：  The star camera optical system is the key technology to achieve high precision performance of the star camera. Based on the engineering practice, the index of image quality evaluation for star camera optical system is combed, and the index decomposition of star point centroid position and the decomposition process of optical system evaluation index are mainly discussed. The analysis shows that: a. both of the centroid position deviation and the central of star point deviation relative to the ideal image height need to be focused on. b. the rise of uniform temperature and the change of gradient temperature need to be taken into account in the optical design process. An example of the star camera optical system design is given, which is based on the double Gauss form, and the aberration theory is applied in the optimization process, with well heat dissipation design and distortion control. The centroid position consistency under different temperature conditions of different types of the fixed stars is analyzed. The results show that the optical system can meet the requirements of highprecision star camera specifications.

Abstract： A prototype inductive pulsed plasma thruster (IPPT) has been developed in the National University of Defense Technology. In order to support the thruster experimental research, a novel fast pulsed gas valve based on eddy current repulsion mechanism is designed and tested in this paper. A new and important design feature is the use of a conical diaphragm as the action part, which greatly contributes to the virtue of simplicity for adopting the resultant force of the diaphragm deformation as the closing force. Experiments are performed over a range of capacitor charge voltages and working gas pressures, and the results reveal that the delay before the valve action is less than 35 μs. The throughput of the valve, which has an upper limit of 2.5 mg argon with a fixed gas pressure of 100 kPa, can be easily regulated by adjusting the charge voltage and the gas pressure. The valve will become a useful tool to facilitate the IPPT research.

Abstract： With helix flying method, GEO helix tourist orbit flies ‘up and down’ around the GEO, with which GEO target and environment’s detection can be realized. In this article, GEO spacecraft’s motion law is analyzed, relative motion between helix tourist orbit and GEO target is analyzed in use of small deviation theory, design method of planar and threedimensional helix circle is given, which can lay the foundation of GEO helix tourist orbit’s design.

Abstract： Control moment gyro（CMG）is one of the significant actuators of spacecraft attitude control system, which can complete the orbit maneuver in high rate, with advantages of large torque control, rapid response, low power consumption and long service life. In this paper, a dynamics model of harmonic drive used in CMG gimbal system is proposed, in which the backlash model of harmonic drive, nonlinear stiffness factor and the efficiency of the reducer are given full consideration. Transmission error is considered in the gear model. Compared with the model without transmission error, the output velocity is more accurate in describing the output curve at low speed. The model of CMG gimbal system is established, and a PID control law is designed to suppress the output transmission error, which is reduced by over 50%. Finally, the effects of the stiffness and damping of harmonic gear on system performances are analyzed based on the simulation model.

Abstract： Daytime star detection algorithm is one of the critical technologies in ship navigation star sensor. The theoretical derivations and the implementation method of the daytime stellar detection algorithm are given based on star maps. Several practical aspects of the algorithms such as the star map filter, the multiframe processing, the index table of blind pixels and the multigradient integral time regulation are designed, to resolve the technical problems like the infrared background noise, the pseudo stars, the detector blind pixels and the adaptability of algorithm with grey background accordingly. The algorithm is effectively verified through field star observation and integrated navigation experiment.

Abstract： During planetary landing, it is an effective method to achieve hazard detection and avoidance by analyzing dense digital elevation map getting from two pictures taken by binocular cameras via matching algorithms. The principles of SAD, fullcensus transformation and sparsecensus stereo matchingtechniques are explained. And an improved SAD algorithm and LOG filter are proposed to overcome the weakness that a simple SAD cannot handle the condition when two pictures have different illumination. Then the algorithms are simulated and compared via stereo images from Middlebury College and sandtable pictures. The matching error rate, the realtime and the usability of the different algorithms are discussed in the scene of planetary landing.