Chang'E-1 Lunar Mission:An Overview and Primary Science Results

Chang'E-1 is the first lunar mission in China, which was successfully launched on Oct. 24th, 2007. It was guided to crash on the Moon on March 1, 2009, at 52.36oE, 1.50oS, in the north of Mare Fecunditatis. The total mission lasted 495 days, exceeding the designed life-span about four months. 1.37 Terabytes raw data was received from Chang'E-1. It was then processed into 4 Terabytes science data at different levels. A series of science results have been achieved by analyzing and applicating these data, especially "global image of the Moon of China's first lunar exploration mission'. Four scientific goals of Chang'E-1 have been achieved. It provides abundant materials for the research of lunar sciences and cosmochemistry. Meanwhile these results will serve for China's future lunar missions.      

新的GPS单频单历元定姿算法

LAMBDA算法依赖于初始的模糊度浮点解,但仅用载波相位观测方程需要多个历元才能获得浮点解,将导致初始化时间过长.针对这一问题,对GPS(Global Positioning System)单历元的载波相位单差方程进行特殊变换,将未知的整周模糊度看成噪声,从而构造出新的观测方程,和原始的观测方程进行组合求解,克服了仅用载波相位双差观测方程因为亏秩而无法在单历元获得浮点解的缺点,解决了初始化时间的问题.通过深入研究浮点解和固定解之间的关系,提出一种将低精度浮点解映射到固定解的方法,降低了LAMBDA算法对高精度浮点解的依赖性,避免了用多个历元获取浮点解的高精度,从而实现了单频、单历元的整周模糊度估计.通过实际测试,该算法成功率高于97%,能够有效地用于实时动态姿态解算.      

增益对星载微波辐射计系统线性度的影响分析

针对星载微波辐射计中检波器的工作特性进行分析. 观测固定目标时, 通过调节AGC (Automatic Gain Control)的大小, 定量分析系统伏安特性曲线, 对星载微波辐射计系统线性度进行定性分析. 结果表明, 通过调节AGC大小, 系统增益发生变化, 导致检波器工作区间发生微弱变化, 通过两点定标不能完全消除由于增益引起的非线性误差. 对一定亮温范围的观测目标进行分析, 结果证明, AGC变化时反算亮温与实际目标亮温差值随观测亮温的变化而成非线性变化. 从而证明, 系统增益变化导致的亮温变化通过两点线性定标并不能完全消除. 在系统正常工作或实时定标过程中, 要尽量避免调节AGC值, 保证微波辐射计系统工作在线性区间.      

考虑互相关干扰的GPS信号捕获门限设定方法

传统GPS卫星信号捕获门限设定方法在互相关干扰情况下存在较大虚警概率,所以无法捕获弱信号.针对该问题进行分析,在此基础上提出一种针对多颗能量不同卫星同时存在情况下的信号检测模型和概率模型.信号检测模型在相关积分非相干累加基础上引入双门限多次检测,由于在考虑噪声的同时也考虑了互相关干扰对弱信号捕获的影响,其概率模型为非中心χ2分布.在原有的恒虚警门限检测方法基础上,提出考虑强信号互相关干扰对微弱信号检测影响情况下的门限计算方法作为新的门限上限,而将原有的门限计算方法作为门限的下限.在此基础上提出强、弱卫星信号共存时的检测思路,即先用门限上限检测强信号并进行互相关干扰消除处理,再用门限下限判断是否有弱信号存在.采用仿真数据和实际数据针对考虑互相关干扰的门限上限进行实验,并和原有门限方法进行比较,证明在强、弱信号共存情况下原有门限无法检测出卫星信号,而新的门限设定方法可以正常工作,并具有较高的检测概率和较低的虚警概率.      

基于RLV飞行过程的氢氧发动机参数设计模型

为了考察氢氧发动机参数选择对可重复使用运载器性能的影响,基于氢氧发动机参数建立了可重复使用运载器入轨飞行过程的计算模型,包括运载器运动方程、飞行控制条件和质量模型,研究了发动机混合比对运载器飞行参数和运载器质量的影响规律.在运载器总质量恒定的情况下,随着发动机混合比由4增大到14,推进剂质量和发动机质量先减小后增大,储箱质量减小,三者的综合效果使得有效载荷质量先增大后减小.      

Remote sensing using GNSS signals: Current status and future directions

The refracted, reflected and scattered signals of global navigation satellite systems (GNSS) have been successfully used to remotely sense the Earth’s surface and atmosphere. It has demonstrated its potential to sense the atmosphere and ionosphere, ocean, land surfaces (including soil moisture) and the cryosphere. These new measurements, although in need of refinement and further validation in many cases, can be used to complement existing techniques and sensors, e.g., radiosonde, ionosonde, radar altimetry and synthetic aperture radar (SAR). This paper presents the current status and new developments of remote sensing using GNSS signals as well as its future directions and applications. Some notable emerging applications include monitoring sea ice, dangerous sea states, ocean eddy and storm surges. With the further improvement of the next generation multi-frequency GNSS systems and receivers and new space-based instruments utilizing GNSS reflections and refractions, new scientific applications of GNSS are expected in various environment remote sensing fields in the near future.     

Theoretical modeling for the stereo mission

We summarize the theory and modeling efforts for the STEREO mission, which will be used to interpret the data of both the remote-sensing (SECCHI, SWAVES) and in-situ instruments (IMPACT, PLASTIC). The modeling includes the coronal plasma, in both open and closed magnetic structures, and the solar wind and its expansion outwards from the Sun, which defines the heliosphere. Particular emphasis is given to modeling of dynamic phenomena associated with the initiation and propagation of coronal mass ejections (CMEs). The modeling of the CME initiation includes magnetic shearing, kink instability, filament eruption, and magnetic reconnection in the flaring lower corona. The modeling of CME propagation entails interplanetary shocks, interplanetary particle beams, solar energetic particles (SEPs), geoeffective connections, and space weather. This review describes mostly existing models of groups that have committed their work to the STEREO mission, but is by no means exhaustive or comprehensive regarding alternative theoretical approaches.     

航空军工企业实行先进制造技术的必然性探讨

航空军工企业要提高研制和生产水平，必须实现制造业信息化，必须发展以信息技术为核心的先进制造技术。积极应用先进制造技术是航空装备战斗力的生成因素，是装备委托方关注的焦点，是国力和国防的后盾。航空军工企业应用先进制造技术，应结合我国国情落实“六坚持”的发展原则。     

“嫦娥4号”中继星中继通信方案研究与分析

中继通信系统是"嫦娥4号"中继星的主载荷和完成任务的关键,须采用合理可行的技术方案,对"嫦娥4号"中继星中继通信系统的方案进行了研究和分析,并给出了设计难点和解决方案,通过Matlab进行了仿真验证,仿真结果表明:提出的解决方案能满足中继星通信要求。     

尾坐式飞行器增益调度控制器设计和比较

针对尾坐式飞行器的动力学模型进行分析,考虑螺旋桨尾流对飞行器的控制作用,建立其数学模型,并针对尾坐式飞行器的纵向转换过渡过程设计了一种基于航迹倾斜角变化的增益调度控制器,分别使用LQR和H_∞两种反馈控制方法经历其增益调度控制器。分别以斜坡和多级阶跃信号为指令,通过以航迹角跟踪的方式进行纵向模型的过渡仿真验证控制器的性能,仿真结果表明,两种控制器均能保证飞行器的稳定过渡转换飞行,且在稳定性方面增益调度LQR控制器具有更好的性能,在快速性和准确性上增益调度H_∞控制器具有更大优势。