Vibrations of circular sandwich plates connected with an elastic foundation

The results of analyzing axisymmetric forced vibrations of an elastic circular sandwich plate connected with an elastic foundation under different surface loads are presented. The hypotheses of a broken normal are accepted to describe the kinematics of a package that is nonsymmetrical over the thickness. The analytical solutions of a problem for plates with a light filler are obtained and numerical analysis is carried out.     

Autonomous navigation of formation flying spacecrafts in deep space exploration and communication by hybrid navigation utilizing neural network filter

Autonomous navigation of spacecrafts is a difficult task, however, which is a must in future deep space exploration. With multiple spacecrafts flying in space, this aim can be achieved by formation flying spacecraft (FFS) utilizing inverse time difference of arrival (ITDOA) and inverse difference Doppler (IDD) methods, which can locate the position of earth-station from one-way uplink signals in the FFS coordinate, and by way of conversion of coordinates, the position of FFS is achieved in earth-centered earth-fixed (ECEF) coordinate. The ability of neural network (NN) filter in navigation to extract position of spacecrafts from random measuring noise of signal arrival time and Doppler shift is studied with different radius of FFS and surveying parameters. The NN filter used by spacecraft group is new way of unidirectional autonomous navigation and is of high precision of hybrid navigation.     

Piloted operations at a near-Earth object (NEO)

In late 2006, NASA's Constellation Program sponsored a study to examine the feasibility of sending a piloted Orion spacecraft to a near-Earth object. NEOs are asteroids or comets that have perihelion distances less than or equal to 1.3 astronomical units, and can have orbits that cross that of the Earth. Therefore, the most suitable targets for the Orion Crew Exploration Vehicle (CEV) are those NEOs in heliocentric orbits similar to Earth's (i.e. low inclination and low eccentricity). One of the significant advantages of this type of mission is that it strengthens and validates the foundational infrastructure of the United States Space Exploration Policy and is highly complementary to NASA's planned lunar sortie and outpost missions circa 2020. A human expedition to a NEO would not only underline the broad utility of the Orion CEV and Ares launch systems, but would also be the first human expedition to an interplanetary body beyond the Earth–Moon system. These deep space operations will present unique challenges not present in lunar missions for the onboard crew, spacecraft systems, and mission control team. Executing several piloted NEO missions will enable NASA to gain crucial deep space operational experience, which will be necessary prerequisites for the eventual human missions to Mars.Our NEO team will present and discuss the following:

• new mission trajectories and concepts;

• operational command and control considerations;

• expected science, operational, resource utilization, and impact mitigation returns; and

• continued exploration momentum and future Mars exploration benefits.

基于X射线脉冲星的深空探测器自主导航方案

X射线脉冲星自主导航系统可以为深空探测器提供位置、速度、时间和姿态等丰富且自主的导航信息,以X射线脉冲星测得的信息作为量测量,结合轨道动力学方程,对航天器的轨道进行自主估计确定。论文阐述了该方案的导航原理,在借鉴现有航天器导航系统的基础上,提出了基于X射线脉冲星导航的方案,介绍了方案的硬件组成、系统结构,并针对方案中导航敏感器多冗余的特征,给出了基于多传感器组合导航技术的结构,最后用仿真资料对方案做了性能概算和精度估计。     

基于深度强化学习的无人机栖落机动控制策略设计

无人机栖落机动飞行是一种无需跑道的降落方法,能够提升无人机在复杂环境下执行任务的适应能力。针对具有高非线性、多约束特性的无人机栖落机动过程,提出了一种基于模仿深度强化学习的控制策略设计方法。首先,建立了固定翼无人机栖落机动的纵向非线性动力学模型,并设计了无人机栖落机动的强化学习环境。其次,针对栖落机动状态动作空间大的特点,为了提高探索效率,通过模仿专家经验的方法对系统进行预训练。然后,以模仿学习得到的权重为基础,采用近端策略优化方法学习构建无人机栖落机动的神经网络控制器。最后,通过仿真验证了上述控制策略设计方法的有效性。     

月球与深空探测频率规划研究

介绍国际电（ITU）和空间频率协调组（SFGC）关于月球与深空探测频率使用的一些规定和建议,研究国外月球与深空探测频率使用规划和发展趋势,探讨我国月球与深空探测频率使用需求,提出我国月球与深空探测频率建议和发展方向。     

天线组阵技术研究及其在我国深空测控通信系统中的应用

研究深空通信系统中天线组阵技术实现方案,并通过数值仿真对几种基本的天线组阵方案和算法的性能进行比较分析。仿真结果表明,采用SUMPLE算法的全频谱合成技术能够获得很好的合成效率,是适合我国深空探测工程测控通信系统设计的有效方案,有望在我国后续的深空探测工程中得到应用。     

航天器深空飞行中的遥控问题

分析了航天器深空飞行中与遥控工作密切相关的信息传输时延,分析了遥控工作面对的控制实时性、控制精度、控制验证等方面的问题;从遥控工作的控制方式、发令工作模式、遥控工作机制、发令时间补偿等方面提出了解决思路。     

Vision and Voyages for Deep Space Exploration

More than 50 years of space exploration has not only satisfied human curiosity and built up international cooperation, but also improved life on Earth. Space exploration is an open-ended process which started 50 years ago. It enables access to unknown terrains with robots and humans, thereby opening new frontiers. Progress of goal deep space exploration was reviewed. China's current deep space missions are also briefly introduced. Focused on the vision and voyages for China's deep space exploration in 5 or 10 years. Like the Chinese Lunar Exploration Program (CLEP), we embark on a journey to Mars. We will spend few decades on Mars with the robotic explorers. Unlike CLEP, scientists proposed to build Moon research station by 2030.     

深空通信中高性能低复杂度的QC-LDPC码构造方法

LDPC码字具有优异的性能, 在空间通信中得到广泛应用. 为进一步降低LDPC码构造及编码的复杂度, 给出了一种高性能、低复杂度的QC-LDPC码构造方法. 设计了扩展近似下三角阵(extern Approximate Lower Triangular, eALT)结构的全局矩阵, 通过增加双对角阵结构全局矩阵的列重, 降低差错平底(error floor). 为降低传统循环移位系数选择的复杂度, 提出了一种基于Zig-Zag的移位系数设计方法, 采用数学公式计算循环移位系数, 无需计算机搜索即可完全消除长度为4的短环. 给出了所构造码字线性编码的实现过程. 仿真结果表明, 所提构造方法在保证线性编码复杂度的前提下, 增大了码字间最小距离, 降低了差错平底, 提高了码字性能; 采用结构化的方法设计循环移位系数, 无需计算机搜索即可消除4环, 所构造的码字与CCSDS标准中的码字在性能相近的情况下, 降低了实现的复杂度.