Quantum navigation and positioning systems require a quantumsatellite information communication system for signal acquisition, tracking, and pointing (ATP). The ATP system is important for quantumsatellite information communication, which involves establishing a quantum communication link and resuming it. Cooperation between coarse and fine tracking can ensure that communication between the two parties attains the desired signaltracking performance. In this paper, we describe in detail the acquisition phase and the coarse tracing technique of quantumsatellite communication for quantum navigation systems. The initial pointing technique, scanning technique, precision and performance of the capture phase are analyzed. Stage precision, its performance index, and other key technologies are also discussed.

Along with spacecraft growing complex, flexible space structures such as large solar panels and large deployable antenna are often applied. To achieve ideal attitude performance and antenna pointing accuracy, vibration control receives much attention. It is worth noticing that flexible space structures often possess close modes at low frequency, which potentially poses problems for the vibration control system. Characteristics and impacts of close modes must be taken into consideration in object modelling, actuators/sensors placement and controller design. In this paper, the reason for modal instability of close modes is first deduced, followed by the proof of model uncertainty caused by this modal instability. Then, based on the singular values of controllability Grammian, the particularity on the controllability of close modes is analyzed. Moreover, the spillover disturbance is demonstrated to show the impact of close modes further. Based on these characteristics, suggestions for vibration control of structures with close modes are proposed, which offers important reference value to onorbit vibration control of flexible space structures.

Star sensors are the most accurate attitude determination instruments in a satellite. The error of star sensor is the key point of the precision of attitude determination system. In this paper, the error sources of star sensor are summarized systematically according to the frequency characteristics. The error analysis, suppression and compensation methods are reviewed so as to provide references for further study. Based on these introductions, the development trend of error suppression and compensation for star sensor’s low frequency error and high frequency error is investigated.

A novel robust active disturbance rejection control approach is presented for a reusable launch vehicle during reentry. The state variables of a general multiinput multioutput model are redefined so that the linear extended state observers of every channel can be designed separately. Then a robust analysis and design methodology is proposed for the active disturbance rejection control system. When this methodology is applied to attitude control, the attitude command is filtered by the steepest tracking differentiator to deal with the contradiction between response speed and antiwindup performance during bank reversal. Simulation results show that the designed control system is well decoupled and quite robust and the saturation problem is solved.

Abstract：Based on intersatellite measurement and reduced relative orbit elements of satellites, an improved approach of formation navigation is investigated. The traditional navigation algorithm transforms the relative orbit elements into the relative position by measuring equations, which results in nonlinearity of the navigation model. In the improved approach, the difference of semiaxis is estimated via the excursion in alongtrack. The problem of linearization error can be solved by using the difference of semiaxis, which has an important influence on relative dynamic of satellites. The method can realize a longterm stable and highprecision navigation of satellites formation.

Abstract：The Stewart platform is used to simulate the microvibration environment in space. The lowfrequency control of microvibration generation is conducted based on the platform. The parameters are tuned repeatedly to get a satisfied performance of the system in the traditional fixedgain controllers. Meanwhile, the nonlinear phenomenon caused by the friction makes it difficult to build an accurate system model. With the problems described above, it is difficult to design the controller for the system. To solve the problems, an adaptive controller is presented. Due to the sensitivity of nonparameter uncertainties, the deadzone technique is used to modify the adaptive laws to improve the robustness. The algorithm is applied to the multidegree microvibration excitation control system. The experimental results show that the platform can generate lowfrequency sinusoidal signal excitations in both onedegree and multidegree direction. The experimental results verify that the method is applicable for practical engineering problems.

Abstract：The dynamical characteristics of tether tugging deorbiting system after the capture by net or gripper are focused on. The modeling and simulation about a simplified configuration in the presence of offset are studied. The combination after capture consists of space tug, tether and space debris. A simplified configuration is proposed, whose attachment point of tether on space debris is viewed as a fixed offset. Then, taking the descending process as an example, the energy equation is given and the dynamic equations of the system are formulated based on EulerLagrange method. The equilibrium point is obtained under proper assumption that the tether is tight. At last, the dynamical characteristics of the system are analyzed with different initial angular velocities when tether is tight or slack. The results demonstrate that a safe deorbiting can be guaranteed when the initial angular velocity of the object satellite is small, and when the initial tether is either tight or slightly slack.

Abstract： The problem of relative position control is addressed for spacecraft formation flying around the SunEarth/Moon L2 libration point. In order to avoid the problem of low precision and dependence on accurate model which occurs when controllers are designed according to linearized models, a relative position control technique is proposed that utilizes the framework of the circular restricted threebody problem. Assuming that the leader spacecraft is in a fixed halo orbit, the position of each follower relative to the leader is controlled to approach to a constant via using the active disturbance rejection control method. In this method, the unknown dynamics and external disturbances of the formation flying system are estimated by an extended state observer, which are compensated by a nonlinear state error feedback control law in real time. The numerical simulations show that the relative position errors obtained by the proposed method are all within the demanding range using the thrust from 0.1 μN to 10 mN. Meanwhile, the proposed method has good robustness against unknown disturbances and shows the superiority in control technique.

Abstract：The task scheduling of spacecraft control software becomes more difficult due to the execution time jitter caused by cache. To deal with this problem, a scheduling design method is proposed based on cyclic executive. The probability distributions of execution times are used to design different system modes with different reliability. Through the mode changes, the processor can be sufficiently utilized and a certain extent degree of reliability is guaranteed. The proposed method can provide useful reference for the task scheduling of spacecraft control software.

Abstract：At present, the detection and recognition of Geosynchronous orbit space target mainly depend on the optical monitoring system to receive the reflected light from the sun. In view of the principle of visible light reflection and the calculation model of visible light reflection characteristic of space object, the design strategy of optical stealth satellite is proposed. The satellite platform configuration, solar panels and hemispherical hood are designed. The whole star shape is simulated and analyzed. Finally the concept of distributed satellites is put forward. The results show that the optical cross section (OCS) peak of the configuration reaches 0.082 m2, which has high concealment and is not easy to be detected and identified by optical monitoring system.

Abstract：In order to improve the maximum rotation angular velocity of electromechanical actuator (EMA) under the light load condition and inhibit the load disturbance, the fluxweakening algorithm for SPMSM adaptive speed adjustment is proposed on the basis of space vector pulse width modulation (SVPWM). Firstly, the speed is improved by the fluxweakening algorithm based on physical power limit, when the power of the system is surplus. Then, for the traditional PI algorithm has the disadvantage of weak dynamic performance when load is changeable, a speed adaptive controller based on Lyapunov stability is presented. Finally, it is proved that the algorithm can realize fluxweakening speed growth, and a good performance of load disturbance inhibition by Simulink simulation.

Abstract：The development of allelectric propulsion platform, the need of different space missions and space constraints make it necessary to develop the multimode operation Hall Thruster. Based on the demand analysis of allelectric propulsion platform for propeller, we discuss the key technologies. It shows that the bottleneck problems are sufficient ionization of working medium，thermal load of thruster and plum focalization under the high specific mode. The development directions of the multimode operation Hall thruster are cathode design technology in wide scope of work condition and nest technology. These need the technical breakthrough about development of the multimode Hall thruster in continuous adjustment of work mode， high specific impulse and large total specific impulse.