Analysis of the Micrometeoroid and Debris Hazard Posed to an Orbiting Parabolic Mirror

Many concepts of future space systems involve the use of parabolic mirrors for optical applications. The need for a highly reflective finish means that performance of such systems will be particularly vulnerable to space debris and micrometeoroids. A case study was performed to examine the micrometeoroid and debris hazard posed to an orbiting parabolic mirror. The mirror considered was nominally Earth-pointed in a circular orbit with two candidate altitudes in low Earth orbit (LEO), well within the region inhabited by man-made debris. The timeframes of interest for the two missions were 2002–2004 and 2005–2015. Microgram and larger particles were considered.To perform this study, it was necessary to determine the debris and meteoroid flux across the parabolic surface. To assess sensitivity of results to uncertainity in available data, two approaches were taken. The first approach was an analytical procedure based on use of long duration exposure facility (LDEF) data and published theoretical results. The second approach used two readily available computer models: the ESA MASTER model and NASA's ORDEM96. In addition, an in-house implementation of the Grün meteoroid model was used. While multiple results were available for the total flux and flux distributed over azimuth, only the MASTER model was available for generating the desired elevation data to obtain the flux distribution over the parabolic mirror. In an attempt to bound the uncertainty in the knowledge of the elevation distribution, the results from both the MASTER and ORDEM96 models were processed together to form a separate, hybrid prediction. In addition, results were used in the preliminary design of a protective skirt.This case study elucidated the practical obstacles and considerations in performing a sufficiently accurate debris and meteoroid analysis using data and tools that are readily available to the broad space sector. The resulting procedures are useful in the assessment of the risk posed to optics by the meteoroid and debris environment and in the design of protection.     

联盟TM交会对接的地面远程导引段制导方法分析与研究

就俄罗斯联盟TM 号飞船与和平号轨道空间站交会对接中的远距离接近段所报导的一些数据对其制导方法进行分析与研究。分析与计算结果表明, 采用固定时间燃料最省的四次冲量方法所获得的冲量大小、方向及冲量施加的时间与报导极为吻合     

载人飞船再入大气层航程控制的模糊控制器设计方法

将模糊控制理论应用于载人飞船再入大气层的落点航程控制问题 ,以纵程误差ΔDR、横程误差ΔCR、剩余时间tcf为输入变量 ,滚动角γv为输出变量 ,得到一个三输入单输出系统的模糊控制器并给出了便于工程应用的设计方法及仿真结果     

1991年6月地磁扰动—地面和同步高度特征

给出了1991年6月地磁扰动的地面和同步高度特征及引起这些扰动的可能的源.在长达近对天的扰动过程中，出现四次主相强度不同的磁暴和多次强急始，有的磁暴由多次扰动迭加而形成形态复杂的复合型磁暴·同步高度Hq分量多次出现反相.这些特征很可能主要是对广大的行星际空间多个高速度高密度结构的响应，这些结构有时伴随大尺度强南向磁场分量.     

太阳电池阵深空探测适应性设计概论

随着近年来月球探测的推进,深空探测的论证,针对深空探测对太阳电池阵低温度、低光强、强辐射等环境的技术需求,以火星探测和木星探测太阳电池阵设计分析为例,通过任务环境特点分析,给出了特殊服役环境下太阳电池选型方法,方阵设计与验证建议,对国内深空探测太阳电池阵设计具有一定参考意义。     

Banach空间中椭圆方程Dirichlet问题的迭代解

以半序理论为工具，在Ｂａｎａｃｈ空间中用上下解方法研究了椭圆方程Ｄｉｒｉｃｈｌｅｔ问题的迭代解，并证明了存在两个迭代序列分别一致收敛于该问题的最小解和最大解。     

基于实时解空间的三维声源定位

提出了一种基于实时解空间库的快速三维声源定位算法。该算法使用来自四个声传感器 ,一个风速传感器和一个风向传感器的信号能够准确快速地计算出声源的位置。     

靶场偏振成像技术应用

偏振成像技术不仅能获取目标的辐射强度信息,还能获取到偏振信息,有助于复杂环境下目标的探测识别.靶场现有光电设备主要采用强度探测,通过目标-环境差别来区分目标,因此,在复杂环境下,目标容易湮没在背景中难以探测.通过分析偏振成像原理和技术特点,总结归纳国外在偏振成像方面的试验应用,阐述了偏振成像在靶场应用的前景和优势,提出了一种基于偏振成像的光学成像系统,并对现有设备提出了偏振化改造方案.通过利用目标、环境的偏振特性,利用强度+偏振的组合模式,可提升现有设备的目标探测和成像识别能力.最后,对偏振技术应用和发展进行了展望.     

Long term and safe relative orbit design for heterogeneous spacecraft clusters

The problem of obtaining long term relative orbit configurations for spacecraft clusters with realistic operational considerations such as safety, station keeping and inter-spacecraft distances is addressed. Two different approaches are developed for station keeping and safety objectives. In the first approach, relative orbit configurations, or relative TLEs, are found minimizing deviations from reference mean orbit which would maximize the station-keeping objective. In second one, relative configurations are found from a reference initial condition by minimizing probability of collision, hence maximizing the safety objective, between the spacecraft in the cluster which are propagated numerically through a high precision orbit propagator. For the design optimization, a derivative free algorithm is proposed. Effectiveness of the approaches is demonstrated through simulations. Using this design framework, several configurations can be found by exploring the limits of the clusters in terms of spacecraft number, distance bounds and probabilities of collision for long time intervals.     

扫描线校正器校正量的实验室测试方法

扫描线校正器（Scan Line Corrector, SLC）是摆扫式成像相机中的重要组成部分，SLC以一定规律转动，使相邻的正、反扫描条带间实现不漏扫和小重叠。为了测试SLC的校正量是否准确，传统的方法是通过外景成像试验实测，但这种方法成本高、周期长，对环境要求也较高。针对此问题，文章研究了在实验室下基于靶标的SLC校正量测试方法。该方法以正、反扫校正量差为中间量，通过建立合适的匹配函数计算出 SLC 校正量曲线的线性起始点，得到 SLC在不同扫描视场的校正量，并通过外景试验验证该方法的正确性。