Abstract：The problems of star sensors relative misalignment calibration and its performance evaluation are investigated. First, an integrated star sensor model including misalignment and measurement error is established. Then, measurement equations for alignment calibration are deduced individually for two different misalignment descriptions, and corresponding estimators are also designed based on Kalman filtering method. Meanwhile, the comparison is present between these estimators when applied to inflight spacecraft calibration. Furthermore, an evaluation method is developed by angle between optical axes of dual star sensors. Finally, the effectiveness of the proposed calibration method is demonstrated by numerical simulations, and the characteristic of inorbit star sensors misalignment relative to each other are also obtained by applying the proposed method with telemetry data．  

Abstract：The application of electric propulsion system in geostationary satellite is widely developed recently. Especially, propellant is saved when electric propulsion system is used in southnorth station keeping. The modified analytical algorithm including GPS ephemeris parameters is presented. Then considering the precise orbit determination including electric propulsion model, a geostationary orbitinjection parameters approach of differential correction is proposed, which can be used in southnorth station keeping based on electric propulsion system autonomously. The effectiveness of southnorth station keeping and the precision of attitude determination are validated with the approach proposed by simulation.

Abstract：In this paper, the adaptive control problem of the collinear threecraft coulomb formation configuration keeping at geostationary orbit is investigated. The nonlinear relative kinetic model of the collinear threecraft Coulomb formation in geosynchronous orbit is established, and the control strategy of only using the Coulomb force as the control force is studied to keep the radial static stability of the collinear threecraft Coulomb formation. Based on the nonlinear dynamic model, considering the unmodeled disturbance force at space environment, the adaptive control law is designed. Finally, the numerical simulation is carried out.  

Abstract：Electric thruster will play a more and more important role with the development of electric thrusters and lowthrustbased orbital transfer. The transfer trajectory optimal design is focused on for Lunar Relay Satellite, which works on the Halo orbit around translunar Libration point L2. Local optimal control for each of the orbit elements is calculated based on Lyapunov feedback control algorithm, and genetic algorithm is chosen to calculate the scalar weights for five orbit elements of transfer trajectory. The result shows the optimal control strategy of transfer trajectory for Lunar Relay Satellite has important engineering meaning.  

Abstract：When mass and force uncertainties are taken into account, it will be difficult for lunar landers to hover on the designed height. To address this problem, we propose a new method for hovering and avoidance which is based on adaption.The core idea is to employ the position as the input of the observer for estimating and compensating the uncertainties. Compared with conventional PID methods, the proposed control strategy enjoys the properties of fast speed and small fluctuation, and it is able to realize high performance for hovering and avoidance. Numerical simulations demonstrate the effectiveness of the proposed approach.  

Abstract：An adaptive nonsingular terminal sliding mode (ANTSM) control method is proposed for trajectory tracking control of space manipulators actuated by scissoredpair control moment gyroscopes (CMGs). Equations of motion are derived by means of recursive algorithms based on Kane’s equations. The nonsingular terminal sliding surface with the tracking error as the variable is constructed to ensure that the tracking error converges to zero in finite time on the sliding surface. The adaptive laws are also proposed for the control gain’s adjustment on account of the uncertainties of the system quality characteristic parameters and unknown disturbances. The control method does not need to know the upper bounds of the uncertainties and the closed loop system is uniformly ultimately bounded. Simulation results verify the effectiveness of the proposed controller combined with the accuracy of tracking expected trajectory and the robustness on the inertia parameter uncertainties and disturbance torque of joints.  

Abstract：Aming at the problems of attitude stability and fuel consumption optimization in the process of attitude control using thrusters, a detailed introduction is made on pulsewidth pulsefrequency (PWPF) pulse modulator and pseudo rate modulator (PSR).The attitude control laws designed with PWPF and PSR modulators are simulated and analyzed respectively, and then the advantages and disadvantages of the two modulators are summarized. By using double time constant to reduce fuel consumption, adding a firstorder inertial filter to reduce the influence of noise so as to improve the attitude control stability, an improved pulse modulator is designed. The simulation results show that the proposed modified pulse modulator is fuel economic and with the same attitude accuracy compared to PWPF modulator. Moreover, the modified pulse modulator significantly improves the accuracy of attitude stabilization compared to PSR modulator.  

Abstract：An orthogonal array experimental design method is developed to optimize the control system parameters of a freefloating space robot manipulator. The experiment results show that it is very quick and precise in approaching the appropriate value of every control parameter with the orthogonal array experimental design method. The method is very useful for optimizing control parameters of complex systems. For example, L81(340) orthogonal array can realize the optimization of fourteen adaptive control parameters which are selected randomly.  

Abstract：In order to investigate the effects of joint clearance and flexibility on dynamic behavior of space manipulator, the rigidflexible coupling models are built on twodegreeoffreedom planar manipulator and sevendegreeoffreedom space manipulator. Furthermore, dynamic amylases of these two models are applied using a nonlinear elasticdamper model of the clearance connections. The effects of the clearance and structure flexibility are discussed detailed. The results show that arm flexibility has a little effect on displacement; however the oscillation of angular velocity and angular acceleration areincreasing with the increasing flexibility. Due to the clearance, the impact changes the dynamic characteristics of space manipulator. Kinematic accuracy decreases and the oscillation of angular velocity and angular acceleration increase with the increasing clearance.  

Abstract：DSP (digital signal processor) is used more and more in the field of space. Considering the complex space environment and longterm reliable operation requirements, the capacity of onboard maintenance becomes an urgent issue which needs to be resolved for spacecraft based on DSP processor platform. Based on engineering practice, a dynamic maintenance scheme for accomplishing DSP software onboard maintenance is designed, and two different methods for generating injection instruction are proposed in this paper. By injecting the generated instructions into an appointed spare memory and enabling the hook code which is embedded in the spacecraft software in advance, the dynamic replacement function of software modules onboard operation is realized. Through the system test, the feasibility of the scheme is proved, and it has good engineering application value.  

Abstract：A novel method which can automatically adjust the freewheeling time of winding current for the largemagnetic torquer is proposed. The problem of the high back emf (electromotive force) generated by the largemagnetic torquer is solved definitely without adding power devices. Adopting the novel method, the size of the circuit board can be reduced significantly and the thermal design of the Drive Circuit becomes simple. And the requirement of frequently changing direction of magnetic torque with small amplitude is satisfied.  

Abstract：To explore a convenient expression of gas flow in the thrust chamber of space rocket engine, the similarity analysis of gas flow in the thrust chamber is carried out. Firstly, a numerical model is built to describe the gas flow in the thrust chamber, and the gas flow velocity and pressure are calculated under typical structure and operating conditions. Secondly, the similarity criteria of gas flow are derived based on dimensional analysis. The dimensionless expression method of gas flow velocity and pressure in thrust chamber is promoted with the similarity criteria. Then the numerical calculation under various structure and operating parameters is organized with an orthogonal design plan. Lastly, the dimensionless expression of gas flow velocity and pressure is obtained with the numerical results as input.