With the development of communication technology and computer network technology, satellite ground stations have varying degrees of construction equipment monitoring system, can manage distribution in different regions of the multi satellite ground station, realized the control equipment unattended, remote monitoring, equipment reliability and stability control were greatly improved. But with the continuous expansion of the application system, the use of increasingly strong demand, the frequency of large task, task closely spaced more and more, the satellite ground station equipment monitoring and control system of timeliness problems continue to appear, the main performance of equipment with a longer time in the satellite earth station, efficiency is not high, in the task of preparing the occupation in large proportion when in use, which restricts the application efficiency of satellite system. This paper analyzes the influence factors restricting the effectiveness of control equipment monitoring system, puts forward the measures and Countermeasures in the future construction of the system, can learn from these methods and apply them, continuously improve the equipment control efficiency.
针对定点在地月系共线平动点附近运动的探测器,研究其轨道预报问题,并探讨了星上外推预报时的力模型简化问题.首先定量分析了共线平动点L1和L2附近探测器的受力情形;然后构造了真实力模型下这些点附近的目标轨道并研究了其误差传播规律,指出这类轨道相比一般卫星轨道预报的不同特征;最后结合星上有限的计算和存储资源限制探讨了力模型的简化问题.此项工作可为定点在平动点附近的探测器的星上预报提供参考.
To increase the computing efficiency of ephemeris prediction for high eccentricity orbit satellites,a variable-step Ad-ams-Cowell integrator with interpolation is proposed in this paper.Used for orbital integration,the method is based on the traditional 8-order Adams-Cowell multi-step method.Based on the characteristics of high eccentricity orbits,variable integral step lengths are adopted at different time in an orbital period.An interpolation formula is introduced to generate ephemerides with a small interval.The proposed method decreases the rounds of satellite motion equation computing,and it is especially ap-plicable for situations where ephemerides are designed to be frequently output.It is validated by using Satellite Tool Kit (STK) High Precision Orbit Propagator (HPOP)model simulation results.Numerical simulation validates the effectiveness and accu-racy of the approach proposed.Examples show that the computing time of the method is far less than that of the traditional multi-step method or HPOP model while keeping a similar accuracy.
A marine environment remote sensing system based on multi-source and multi-destination Global Navigation Sat-ellite System-Reflections (GNSS-R)technology is introduced in this paper.The system was independently developed and used in three airborne flight tests in specific area of Bohai Bay near Tianjin.A significant amount of effective GNSS-R signal data was collected and significant wave height under natural conditions was retrieved.The system received GNSS direct sig-nals and reflected signals of the sea,then generated Delay-Doppler Mapping (DDM)imagery by correlation process of the signals.Correlation power waveform of the DDM map was calculated using Derivative of the Correlation Function (DCF). Then,significant wave height was calculated through DCF waveform width.Feasibility of the method is verified.It worked under all-weather and all-day conditions with the advantages of high resolution and low cost,demonstrating significance for monitoring small and medium scale ocean states and physical phenomena.
Based on analysis on the present research status of the lunar and deep space Tracking,Telemetry and Command (TT&C) systems at home and abroad,four major difficulties and challenges for building a TT&C system are studied.Then urgent needs for antenna arraying technology,laser TT&C technology,Ka and millimeterwave band hypothermia receiver,superconducting nanowire single photon detectors,deep space optical tracking system,narrow linewidth laser source generating technology,optical communication modulation technology and highpower low-noise amplifier were summed up.A latest cutting-edge technology for deep space TT&C system,namely Integrated Radio and Optical Communications (IROC) system was described.Finally,with the current situation,recommendations for future developments of lunar and deep space TT&C systems have been put forward.The research results provide references for the development of the lunar and deep space TT&C systems.
针对空间机器人对捕获部位识别方法的普适性、实时性和准确性等要求,提出了采用深度学习方法对空间机器人捕获目标的特征部位进行识别.通过比较分析方法、数据驱动方法等传统识别方法和深度学习方法的优缺点,发现深度学习方法对于解决空间机器人捕获部位识别问题具有显著优势.进一步分析了应用深度学习方法解决捕获部位识别问题的几个关键技术问题,为后续空间机器人在轨捕获目标的研究与实践提供了新的思路.
With the rapid development of China's manned space flights,Beidou navigation and Low Earth Orbit (LEO) constellation system,Tracking and Data Relay Satellite (TDRS) provides a fundamental solution to solve the long time,high coverage and multi-satellites Tracking,Telemetry and Command (TT&C) problems for its space-based design thinking.In this process,parameters such as time delay of user satellites to relay satellites and correction error of Doppler frequency shift will bring interference to multi-object TT&C.In order to solve this problem,this paper analyzes factors such as time delay,Doppler frequency shift correction error due to positioning error,design S-band Multiple Access (SMA) signal form of forward link and reverse link based on the multi-object,choose Large Area Synchronous (LAS) code matching the time delay correction error as the spread spectrum code of the reverse telemetry information,and then proposes a navigation aided terminal delay and frequency pre-correction scheme model,which can eliminate multi-user interference effectively.Simulation results show when Eb/N0 of reverse link is more than 10.5 dB,the bit error rate of telemetry information is less than 1 × 10-6,which is economized 2 dB compared with Gold sequence.It provides an important reference to space-based TT&C for the stable operation of satellites in orbit,manned space rendezvous and docking and subsequent space station construction,etc.
In order to obtain the micro-Doppler information of space targets,the high-speed translational component of radar echoes needs to be compensated accurately.In regard to the problem of space target high-speed motion on the extraction of micro-motion information,the impact of micro-Doppler frequency modulated by space target translation is analyzed.High speed translation of targets,especially translational acceleration,which can directly lead to target Doppler spectral broadening characteristics,will interfere with the conclusion of the micro-Doppler frequency extraction.On the basis of this,a translational motion parameter estimation method based on image quality is proposed.Finally,the multi-scattering center model of space target is used to carry out translational compensation analysis.The simulation results verify the effectiveness of the method.
Gravity deformation of large reflector antennas causes deterioration of antenna performance.To solve the problem,a method of realtime adjustment of subreflector to reduce the influence of gravity deformation is proposed in the paper.The influence of the position translation and rotation of subreflector on antenna gain and pointing is an-alyzed.A mathematical model about the posture change of subreflector with the adjustment of antenna elevation an-gle is built.A set of data about the main reflector deformation of 35 m antenna for different elevation angles was ob-tained through digital photogrammetry.The best fit was conducted.Then,a set of optimum position coordinates of subreflector obtained through best fit were superposed with the measured displacement data of subreflector under the action of gravity with respect to different elevation angles.Next,a set of final adjustment data of subreflector was obtained and substituted into the mathematical model.The best fit was conducted again by using least squares to calculate parameters of the mathematical model.The model was used to adjust subreflector in realtime to reduce the influence of gravity deformation on antenna performance.Simulation results show that the gain of a 35 m antenna in X band and Ka band can be increased by 0.52 dB and 1.95 dB after subreflector position is adjusted in realtime by u-sing the model.
Mars relay technology is becoming more and more mature since Mars Global Surveyor injection and providing data relay service.It is widely used to provide navigation and Tracking,Telemetry and Command (TT&C) for Mars Entry,Descent and Landing (EDL) and to assure telemetry,command and huge volume science data transfer in Mars surface exploration.It has been taken as an important part of Mars exploration by National Aeronautics and Space Administration (NASA) and European Space Agency (ESA).The basic composition and working state together with the successful experience and achievements of NASA and ESA are introduced.The focuses are shown on the specifications of Mars relay radio equipments on Mars orbiter and lander.The follow-up of this technology is introduced to provide reference to further research in China Mars exploration.
时间同步在通信、计算机、测控等网络中是一项重要技术.针对目标时钟在多同步源时的时间同步问题,从统计学中参数估计的角度建模,提出了一种基于WMLR(Weighted Multiple Linear Regression,加权多元线性回归)的两步式时间同步算法.此算法分为粗同步和精同步2个阶段,通过给不同的时间信息加权的方式提高同步精度,并且可以计算不同同步源之间存在的系统误差.结果 表明,这一算法通过合理应用来自不同同步源的时间信息,可以提高时间同步的精度及稳定性.由于模型的普遍性,这一基于WMLR的算法也可以应用于其他类似的多源参数估计的场景中.
Non-Orthogonal Multiple Access (NOMA)has broad application prospects in space information transmis-sion as it increases system throughput and spectral efficiency. Synchronization issues and mutual interference be-tween different users are main problems for NOMA receivers. To solve the problems,we propose an asynchronous interference cancellation method for NOMA. First,an oversampling method that brings independent noise samples is presented. Then,by taking advantage of the good structure between the oversampling output sequences,we re-spectively implemented Successive Interference Cancellation (SIC ), Belief Propagation (BP ) detection and Maximum-Likelihood Sequence Detection (MLSD). Simulation results show that symbol asynchronous NOMA outperforms synchronous NOMA.
A phase-coherent Direct Sequence and Frequency Hopping (DS/FH) spread-spectrum signal has a much wider bandwidth than simple DS spread spectrum signals.Due to the non-linearity of ionosphere and frequency hopping scheme of the signal,Binary Phase Shift Keying (BPSK) Bit Error Rate (BER) deteriorates.Under the assumption of pure background ionospheric dispersion and a uniformly-distributed FH pattern,the BER of both the pilot signal and the long term signal in a specific DS/FH satellite link are acquired through using mathematical tools concerning the probability density functions of Random Variables (RVs).Simulations under constant ionospheric dispersion and uniformly-distributed FH pattern scintillation conditions are carried out to verify BER results.
According to the experimental design of naval gun weapon system for qualitative target,low altitude flight speed does not drop down and small route short-cut for target is difficult to achieve high risk,so the evaluation standard is low,it is difficult to carry out effective full assessment and other issues of naval gun weapon system.The factors affecting the target damage probability analysis from the test target for shipborne weapon system for target speed,height,route shortcut,calculation model of damage probability is established,through the actual calculation demonstrates the close in antimissile shipborne antiship missile intercept target,if the target of low speed,high altitude,large shortcut for this target,the probability of damage will obviously increase,which leads to the decrease of the weapon system evaluation standard.In order to combat effectiveness assessment of real weapons,using high speed,flying over the sea,a small target route shortcut target intercept test,to fully,solve the boundary condition test,to achieve the purpose of strict examination.
In realtime traj ectory estimation based on Unscented Kalman Filter (UKF),the influence of unstable ex-ternal environment and existence of outliers made filtering results inaccurate or even divergent. Therefore,it was necessary to adj ust and determine values of filter parameters properly to overcome the problem before a missile launch. A robust design of filter parameters based on theoretical traj ectory as prior information was proposed to pre-dict the optimal value of parameters. Starting from the perspective of filter framework,this paper selected relevant parameters,adopted the idea of robust design,constructed a ballistic measurement model through simulating trajec-tory feature points based on theoretical traj ectory in outer design;and carried out orthogonal experimental design by reversing measurement data from constructed model,then j udged the significance of the parameters and determined its optimal value,so as to give guidance to parameter setting of realtime traj ectory estimation. Examples show that this method is of high validity,and can improve the robustness and convergence performance of the filter.
A lot of research at home and abroad used genetic algorithm on the problem of space Tracking,Telemetry and Command (TT&C) resource scheduling,which is a kind of time window limited constraint satisfaction problem,and good effects are achieved.But most proiects focused on Low Earth Orbit (LEO) spacecraft which has a short visible pass and the total pass is tracked usually,without considering High Earth Orbit (HEO),which has long visible pass and usually only part of it is tracked.Aiming at the characteristics of spacecraft TT&C resources unified allocation for HEO and LEO spacecraft,a multi-dimension genetic encoding method is promoted to describe this problem.The corresponding elements of the algorithm including crossover operator and mutation operator are defined as well so that a multi-dimension genetic algorithm is built to solve the resources allocation problem.Simulation results show that this algorithm effectively solves the problem of TT&C resources management and unified allocation for LEO and HEO spacecraft,as required by the current domestic managing mode of "one net for multi-spacecraft".
Aiming at the problem of heavy equipment and slow tracking in Unmanned Aerial Vehicle (UAV)Track-ing,Telemetry and Command (TT&C)and information transmission system,the method of smart antenna is pro-posed for ground antenna. The Directional Arrival (DOA)estimation of the airborne terminal is realized by the Multiple Signal Classification (MUSIC)algorithm,and the decorrelation is added to against multipath. Compared with the traditional mechanical tracking mode,it has the advantages of light weight,low cost,high maneuverability and fast tracking. Simulation and actual test results show that the smart antenna with DOA estimation and beam-forming algorithm can accurately estimate the direction of the incoming signal of the desired signal and multipath signal in real time while ensuring the high gain,and accomplish the beam pointing correctly. It has a high value of engineering applications.
This paper proposes a new realtime classification algorithm for multi-velocity measurement data under response mode to improve target trajectory stability.First,this paper analyses the defects of the existing method.Second,it designs a new classification algorithm which can classify response data,beacon data and abnormal data.The key of the new algorithm is selection of suitable classification references.Theoretical trajectory and classified real measurement data at historical moments are used as classification references in different situations.Finally,the new algorithm is validated with two kinds of typical real measurement data corresponding to two kinds of master stations configuration mode,and the results show that the algorithm can classify three kinds of data correctly.On this basis,the realtime trajectory calculated is smooth and continuous and data utilization is evidently increased.Therefore,the new classification algorithm of this paper is better than the existing method and it has guiding significance for improving realtime data classification in different measurement systems.
Based on study of the principles and development of network coding,the survey analyzes its applicable techniques in the physical-layer of wireless communication systems and focuses on Physical-layer Network Coding (PNC)and the joint design of channel coding and network coding techniques. On one hand,the survey firstly intro-duces the mechanism of PNC and then summarizes the current results and future directions of the following classi-fied hot topics:coding and decoding design,synchronization problem,combination with other transmission tech-niques,PNC capacity and application scenario extensions of PNC. On the other hand,the survey reviews the joint design techniques of channel coding and network coding in accordance with different starting points which are induc-ted as basing on the type of channel coding,modifying the mode of handling soft information,utilizing of PNC and considering various system scenarios.
A three-layer "data pool"- "data table"- "data channel"transfer software frame with highly abstract data,high generalization degree disposal process and strong adaptability was proposed in this paper to meet challen-ges of multiple data kinds,flexible data receiving and sending modes,frequent techno-state changes and high stand-ard software maintenance.The telemetry data transfer software has already been implemented in Kylin operating system based on this frame.All kinds of aerospace measurement task demands can be met through quick and visual configuration.Applications show that the frame is an ideal and efficient general solution of data transfer software and can be migrated to radar,optical and other measurement equipment.
