Space is the new frontier of a country. Space activities are important embodiment of national will and strategic intention, and important guarantee for the expansion of national interests. Space security has become an important part of national security. Space situation awareness refers to the acquisition and cognition of space situation information, including space target monitoring and space environment monitoring. It is the basis for further space control and space confrontation. Firstly, this paper reviews the development of relevant regulations in the field of space situational awareness, introduces the implementation of several typical situation awareness projects in the field of high orbit in the United States, and summarizes four key technologies, including space entry, autonomous operation, rendezvous and docking navigation and control, and multi angle stereo imaging technology. Finally, this paper gives some suggestions on the establishment of situation awareness system, spacebased autonomous sensing system, and the development of space attack and defense confrontation capability.

According to the mission requirements and planning of the first China mission exploration, the gravity gradient torque and solar pressure torque are investigated by considering the orbiter mass property, configurations, and the highly eccentric orbit. The accumulation of the disturbance torques can increase the rotational speed of the flywheels and finally decrease the attitude maneuver capability. Therefore, the momentum unloading utilizing active thrust forces are usually required. To reduce the number of the momentum unloading, a method based on attitude bias is developed to achieve the canceling effect of gravity gradient torque and solar pressure torque. The numerical simulation results indicate that the accumulation of the disturbance torques can reduce to 70 percent, making a contribution to saving on fuel and promoting longer life of the spacecraft.

The control of threesatellite Coulomb hybrid formation in geostationary orbit is studied in this paper. Firstly, the dynamic equation of hybrid propulsion threesatellite coulomb formation in geostationary orbit is established by considering the influence of unknown bounded relative perturbation. Then, the rotation formation configuration of projected circular orbit is designed based on the relative motion analytic solution. Finally, the sliding mode control method is adopted to design the controller and prove its stability. The saturation function is used to improve the controller and eliminate the influence of chattering. The preset formation can be maintained by controlling the internal electrostatic force and supplementary electric thrust. Simulation results show that the hybrid propulsion scheme has fast response speed and high control precision, and meets the control requirements.

The phase maintenance method is introduced for a nearcircular LEO satellite constellation without orbital altitude maintenance requirements in this paper. According to the orbit perturbation theory, the satellite phase drift model considering J2 perturbation and atmospheric drag perturbation is derived, and then two expression methods of phase deviation based on fixed reference satellite and virtual reference satellite are given respectively. On this basis, the theoretical and practical control quantity considering actual control errors are given for the two cases of orbit decay rate consistent and inconsistent. Finally, the effectiveness of the two methods are verified by a LEO Walker constellation simulation example. The results show that the two methods can effectively complete the phase maintenance task. The two methods have no significant difference in the number of times of control and the total amount of control in the case of orbit decay rate consistent. But in the case of orbit decay rate inconsistent, the phase maintenance strategy based on a fixed reference satellite is better.

Space mechanical structures tend to be largescale, complex and flexible, which easily leads to residual vibration, and the frequency of residual vibration is low and the vibration time is long. Aiming at the residual vibration problem of multi flexible beams coupling structure, the dynamic model is established by finite element method, and the vibration characteristics are analyzed, showing the characteristics of dense frequency and beat frequency. For the residual vibration problem, combined with fuzzy reinforcement learning control algorithm, the fuzzy rule table is constructed. The action in each rule is selected by εgreedy method, and the control voltage is generated in the end. The feedback learning of stateaction value is carried out via temporal difference (TD) error. After training, the controller converges to a fuzzy control rule. The simulation results show that the fuzzy reinforcement learning controller can quickly suppress the residual vibration of multi flexible beams, and verify the effectiveness of the fuzzy reinforcement learning control algorithm.

To solve the problem of gimbal control performance decreasing caused by flexible support disturbance in control moment gyroscope (CMG), a dynamic model of single gimbal control moment gyroscope (SGCMG) with flexible support is estabished, the coupling mechanism of the disturbance with the influence of flexible support is analyzed and the analytical model is given. Based on modeling and analysis, an integral sliding mode control strategy is adopted to achieve strong robustness to gimbal dynamics changes and new disturbance torque. Simulation results show that the proposed control strategy realizes better dynamic process and steadystate performance comparing with PID control strategy, and improves the closedloop control performance of control moment gyro gimbal system under flexible support.

The relative navigation using only lineofsight (LOS) information has the advantages of simple equipment, low complexity, and low power consumption, and has a wide range of applications in space missions. This paper proposes a space target detection method based on ordering points to identify the clustering structure (OPTICS) clustering in the view of the fact that there are few features of space noncooperative targets during the relative navigation with only angle measurement at medium and long distances. The raw image collected by the star camera is preprocessed to extract star points and target points, and some frames are selected according to the result of star identification. The improved OPTICS clustering method is used to obtain the target trajectory. Finally, to confirm the algorithm's effectiveness, it is used to process the highprecision star map containing the target simulated by the software simulation. The proportion of horizontal and vertical errors less than 0.15 degree is 85.4% and 99.6% during the progressive process. Compared with the target detection method in autonomous vision approach navigation and target identification (AVANTI) experiment, the adjustment of related parameters in the onorbit mission is reduced, and the autonomy of the algorithm is improved.

According to the rules of satellite orbit resource of ITU, the satellite operator may move a satellite to another different orbit position and keep it for at least 90 days to enable the frequency assignment of the orbit slots. This kind of orbit maneuver is called “spectrum/orbit occupation” which is a common phenomenon of communication satellites. The INTELSAT series satellites are chosen as the research object via two line elements (TLE) and SGP4/SDP4 model to calculate 67 INTELSAT's orbital data. And the method based on density and knearest neighbor outlier detection is proposed to filter data outliers, which can improve the data accuracy. Counting and analyzing these satellites' spectrum/orbit occupation, it is proposed that Chinese satellite operators should take advantage of international rules to safeguard space rights.

In orbit, when spacecraft are placed in eastwest direction and northsouth direction, they are in lateral microgravity environment which makes the propellant reorientation get sloshing easier. And higher requirements are put forward for the management capability of the propellant management device (PMD) in lateral microgravity environment. A large number of simulations and experiments are needed to verify the performance of PMD in order to ensure the inorbit fluid management performance of the vane tank. Taking vanetype surface tension tank as research objects, the VOF (volume of fluid) twophase flow model is used to simulate the propellant movement process under the reorientation process in the lateral microgravity environment and analyze the propellant sloshing behavior in the process. In the end, the results of numerical simulation verify the management capability of the vanetype surface tension tank which can provide reference for the drop tower experiments and the space station tests.

In this paper, an adaptive backstepping control with improved interval type2 fuzzy neural networks approximator is proposed for doublelink manipulator system. Compared with type1 fuzzy system, interval type2 fuzzy system can obtain better performance for highly complex nonlinear systems because of its uncertainties in the antecedent and membership functions. However, KM algorithm in the process of finding the cross points between upper output and lower output in type2 fuzzy system leads to heavy computational burden and time consumption which makes it difficult to apply in practical engineering. In this paper, instead of KM algorithm, an adaptive factor is used to build an adaptive ponderation between upper output and lower output. The improved interval type2 fuzzy neural networks approximator is applied to handle the uncertain parameters in doublelink manipulator system. The ultimately boundedness of all signals and the stability of the closedloop system can be mathematically proved by the Lyapunov stability analysis. The simulation results demonstrate the proposed adaptive backstepping control with improved interval type2 fuzzy neural networks approximator obtains transient response, short stabilizing time and high approximation accuracy.

To implement highprecision relative navigation during the descent and landing phase of asteroid exploration, a landmarkbased relative navigation method is proposed. The predicted image of the landmark map(Lmap/maplet) is first rendered by the stereophotoclinometry (SPC) illumination model, and the extracted image of the maplet is then generated from the observed image using bilinear interpolation. The combined correlation matching method is adopted to perform exact matching between the predicted image and the extracted image, and obtain the observed image location of the landmark center accurately. Therefore, the camera pose is estimated by the perspectivenpoint (PNP) algorithm. The simulation results show that this method can achieve subpixel accuracy even when the initial camera pose deviation is slightly large, and it has good realtime performance.

The thruster need to be switched if some kind of fault in spacecraft control system occurs. Spacecraft thruster switching takes multiple software control cycles to complete, so it can’t be interrupted during execution. The sequence conflict and failure of thruster switching due to crosscoupled occurrence of multiple fault disposals are fully analyzed. A software mutually exclusive design method is presented in this paper for thruster switch failure. Simulation results show that this method is feasible.