China's Deep-space Exploration to 2030

Focusing on the key scientific questions of deep space exploration which include the origin and evolution of the solar system and its planets, disastrous impact on the Earth by the solar activities and small bodies, extraterrestrial life, this paper put forward a propose about the roadmap and scientific objectives of China's Deep-space Exploration before 2030.

Network Evaluation and Protocol Deployment for Complex Deep-Space Networks Based on DTN

Previous research on deep-space networks based on delay-tolerant networking(DTN)has mainly focused on the performance of DTN protocols in simple networks;hence,research on complex networks is lacking.In this paper,we focus on network evaluation and protocol deployment for complex DTNbased deep-space networks and apply the results to a novel complex deep-space network based on the Universal Interplanetary Communication Network(UNICON-CDSN)proposed by the National Space Science Center(NSSC)for simulation and verification.A network evaluation method based on network capacity and memory analysis is proposed.Based on a performance comparison between the Licklider Transmission Protocol(LTP)and the Transmission Control Protocol(TCP)with the Bundle Protocol(BP)in various communication scenarios,a transport protocol configuration proposal is developed and used to construct an LTP deployment scheme for UNICON-CDSN.For the LTP deployment scheme,a theoretical model of file delivery time over complex deep-space networks is built.A network evaluation with the method proposed in this paper proves that UNICONCDSN satisfies the requirements for the 2020 Mars exploration mission Curiosity.Moreover,simulation results from a universal space communication network testbed(USCNT)designed by us show that the LTP deployment scheme is suitable for UNICON-CDSN.

Smart Communications and Networking for Future Deep-space Exploration

eight planets,various asteroids and comets in the solar system.Amount of deep-space scientific experiments promoted people to understand about the origin and evolution of the universe.With the rapid developments of equipment and spacecraft with high-accuracy detector and long-term energy,more and more ambitious deep-space exploration plans have also been scheduled or under discussion about space resources utilization and space migration,e.g.,manned landing on the Mars,guard infrastructures on the Moon and human-flight to the edge of the solar system(>100 AU),etc.

Application of the sun line-of-sight vector in the optimal attitude estimation of deep-space probe

This paper proposed an optimal algorithm using the sun line-of-sight vector to improve the probe attitude estimation accuracy in deep-space mission.Firstly,the elaborate analysis of the attitude estimation error from vector observations was done to demonstrate that the geometric relation between the reference vectors is an important factor which influences the accuracy of attitude estimation.Then,with introduction of the sun line-of-sight vector,the attitude quaternion obtained from the star-sensor was converted into a pair of mutually perpendicular reference vectors perpendicular to the sun vector.The normalized weights were calculated according to the accuracy of the sensors.Furthermore,the optimal attitude estimation in the least squares sense was achieved with the quaternion estimation method.Finally,the results of simulation demonstrated the validity of the proposed optimal algorithm based on the practical data of the Deep Impact mission.

基于数字信道化的极微弱信号载波频率引导模块设计与实现

针对深空探测中常规点数的FFT无法对极微弱信号进行精确的频率引导,而超长点数的FFT无法用现有器件实现,提出一种基于数字信道化的并行FFT频率引导方法。接收信号先经过数字信道化处理,均匀划分为若干窄带信号,然后分别对各子带信号进行FFT运算,最后通过对各子带有效谱线的联合检测完成载波频率的精确估计。在等效219点FFT的频率引导模块FPGA实现中,通过FFT模块的复用节约了硬件资源开销。测试结果表明:在8MHz采样率下该模块的测频精度小于10Hz。

文学“内、外”理论及其重释

文学“内、外”理论是指俄国形式主义理论家什克洛夫斯基和美国新批评理论家韦勒克缔造的关于文学的“内部规律/外部规律”、“内部研究/外部研究”的理论。以一种非本质主义的、整体主义的思维方式审视文学的存在整体,以现象学的方法建构文学的存在方式,在此基础上阐释文学“内、外”理论,更具科学性、合理性。

Recent Advances in Space-Deployable Structures in China

Deployable space structure technology is an approach used in building spacecraft,especially when realizing deployment and folding functions.Once in orbit,the structures are released from the fairing,deployed,and positioned.With the development of communication,remote-sensing,and navigation satellites,space-deployable structures have become cutting-edge research topics in space science and technology.This paper summarizes the current research status and development trend of spacedeployable structures in China,including large space mesh antennas,space solar arrays,and deployable structures and mechanisms for deep-space exploration.Critical technologies of space-deployable structures are addressed from the perspectives of deployable mechanisms,cable-membrane form-finding,dynamic analysis,reliable environmental adaptability analysis,and validation.Finally,future technology developments and trends are elucidated in the fields of mesh antennas,solar arrays,deployable mechanisms,and on-orbit adjustment,assembly,and construction.

Hyperbolic orbit and its variation of deep-space probe

While approaching the target body, the deep-space probe is orbiting hyperbolically before the maneuver. We discuss the variation of perturbed hyperbolic orbit using the method similar to that used in elliptic orbit. Ephemeris calculating and orbit control will benefit from the given analytical solution.

Modeling the RTT of bundle protocol over asymmetric deep-space channels

Delay/disruption-tolerant networking communications rely heavily on BP(Bundle Protocol),which uses the well-known approach of store-and-forward with optional custody transfer to deal with stressed communication environments.The use of BP and its performance in deep-space communication has been the subject of debate.The accurate estimate of file delivery latency(i.e.,RTT(Round Trip Time))is essential for efficient transmission control,reliable delivery,and bandwidth usage optimization of a protocol.In this paper,we present a performance analysis of BP running over UDPCL/UDP over deep-space channels,focusing on the RTT estimate,in the presence of highly asymmetric channel rates.Analytical models are built for the RTT estimate of the BP/UDPCL transmissions considering the effect of delay caused by space channel-rate asymmetry,and,channel impairment.The models are validated by file transfer experiments using a PC-based testbed.It is found that a smaller bundle size(if smaller than a calculated threshold)results in a longer delay in custody acknowledgment transmission,and thus,a longer RTT.

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New high-accuracy spacecraft VLBI tracking using high data-rate signal:A demonstration with Chang'E-3

As the scientific data volume in deep-space exploration rapidly grows,spacecraft heavily relies on high data-rate signals that span several megahertz to transmit data back to Earth.Employing high data-rate signals for high-accuracy radiometric interferometry can simultaneously deal with data transmission and spacecraft navigation.We demonstrate very long baseline interferometry(VLBI)tracking of the Chang’E-3 lander and rover to determine their relative lunar-surface position using downlink high data-rate signals.A new method based on the VLBI phase-referencing technique is proposed to obtain the differential phase delay,which is much more accurate than the differential group delay acquired by conventional VLBI approaches.The systemic errors among different signal channels have been well calibrated using the new method.The data from the Chang’E-3mission were then processed,and meter-level accuracy positions of the rover with respect to the lander have been obtained.This demonstration shows the feasibility of high-accuracy radiometric interferometry using high data-rate signals.The method proposed in this paper can also be applied to future deep-space navigation.

Concept of the Solar Ring mission: Preliminary design and mission profile

The Solar Ring mission, a concept to monitor the Sun and inner heliosphere from multiple perspectives, has been funded for prephase study by the Strategic Priority Program of Chinese Academy of Sciences in space sciences. The Solar Ring is comprised of 6 spacecraft, grouped in three pairs, moving around the Sun in an elliptical orbit in the ecliptic plane. The mission costs,including launch fee, deep-space maneuvers, and deployment time of the ring, are highly relevant to the working orbit, deepspace transfer, and phase angle within a group. The preliminary mission profile is analyzed and designed in this paper. The launch way, two spacecraft with one rocket, is adopted. The deployment time, phasing maneuvers, and C_(3) of launch energy are evaluated for the elliptical orbits with the perihelion between 0.7 and 0.9 AU using the rockets of Long March(LM) 3A and 3B.Numerical simulations show two candidate trajectories: fast deployment within 4 years by LM-3B, medium deployment more than 6 years by cheaper rocket of LM-3A. In order to obtain both fast deployment and low launch cost, another orbit profile is proposed by shortening the phase angle within a group. The suggested working orbits and the corresponding costs of launch,deployment time, and phasing maneuvers will strongly support the science objectives.