Long-term photometric signature study of two GEO satellites

Geostationary earth orbit satellites have been extensively used for unique high-orbit stationary characteristics. Long-term precise investigation is an important issue in the observation of GEO satellites, since it can provide valuable information on the satellites’ operation state, discrimination and early warning analysis. Ground-based optical-electronic devices play a significant role in the observation. 4-month photometric signature variation of two satellites is presented based on the successive observations using the 1.56-meter telescope of Shanghai Astronomical Observatory (SHAO). It can be concluded that the long-term brightness change mainly results from the sun declination angle and regular orbit maneuver. Moreover, the solar panel offsets of the two satellites are analyzed and found to be approximately 4 degrees. Estimation of photometric accuracy reaches 0.15 mag for the application of CCD drift-scan optical-electronic technique.     

空间碎片环境工程模式参数分析

为了评估空间碎片对航天器造成的危害 ,必须建立空间碎片环境工程模式。文章介绍了空间碎片环境的特点及其工程模式表征方法 ,并比较、分析了几种主要空间碎片环境工程模式的参数 ;从数学建模及风险评估应用的需求出发 ,提出了空间碎片环境工程模式参数的建议方案     

一种面向产品规划过程的组合质量屋

针对现代产品设计规划过程中对规划信息的集成性、准确性和完备性的要求,提出了一种面向产品规划过程的组合质量屋,并给出了构建组合质量屋的过程和方法.该组合质量屋包括用户需求质量屋、产品技术特性质量屋和综合质量屋.在构建组合质量屋的过程中,采用网络分析法确定产品技术特性的相对重要度,该方法能综合考虑用户需求间、产品技术特性间以及用户需求层和产品技术特性层之间的相互协作和相互冲突的关系,使得规划结果更加准确可靠.此外,还综合考虑了产品全生命周期各阶段定性和定量约束对规划结果的影响.最后,通过实例研究了运用组合质量屋进行产品规划的步骤和方法,并验证了其有效性.      

有限推力轨迹优化问题的直接打靶法研究

研究了求解有限推力轨迹优化问题的直接打靶方法。说明了利用直接打靶法将最优轨迹问题转化为参数优化问题的基本转换方法 ;给出了状态和控制变量的等式 (或不等式 )约束的转化方法 ;从插值和数值积分两个方面对转换过程中产生的误差进行了深入分析。最后 ,以最优交会问题为例 ,说明了不同节点数目和积分步数对计算结果的影响     

双框架控制力矩陀螺群的建模与分析

 研究采用双框架控制力矩陀螺群在卫星高精度姿态控制中的建模问题。对于中心刚体带有多个双框架控制力矩陀螺,构造了该系统的拉格朗日函数。采用拟拉格朗日方程建立了卫星姿态动力学模型。在建模中,陀螺的内、外框架未进行无惯量的假设,使得双框架运动带来的动力学特性得到了准确的反映;设计了适宜的标记,使得方程形式简洁并且统一。该模型为高精度的数学仿真和分析提供了基础。基于系统的拉格朗日函数,应用拉格朗日方程,分别建立了沿内、外框架轴和转子轴的轴向动力学方程,为执行机构伺服系统的动力学特性分析和控制器设计提供模型的依据。     

飞机数字化装配工艺仿真技术

利用产品的三维数字样机,对产品的装配过程统一建模,在计算机上实现产品从零件、组件装配成产品的整个过程的模拟和仿真.这样,在建立了产品和资源数字模型的基础上,就可以在产品的设计阶段模拟出产品的实际装配过程,而无需实物样机.     

面向开发过程的产品结构形式化建模

为满足开发过程产品结构数据的动态结构配置、动态任务协作、动态目标求解、动态状态跟踪等应用需要,在对开发过程产品结构属性及其相互关系进行分析的基础上,提出了一种面向开发过程应用的产品结构形式化模型.结合产品开发活动的时域行为特征,给出了产品结构的时域定义,并以此为基础构建了产品结构模型的时域扩展定义.通过分析产品状态与开发任务时域行为的映射关系,在产品结构时域扩展定义的基础上,提出了基于时间截面的开发过程产品结构状态追踪方案及算法,并通过模拟产品对象在开发过程中的状态变迁过程,验证了模型及相关应用方案的实用性和有效性.      

A reappraisal of the habitability of planets around M dwarf stars

Stable, hydrogen-burning, M dwarf stars make up about 75% of all stars in the Galaxy. They are extremely long-lived, and because they are much smaller in mass than the Sun (between 0.5 and 0.08 M(Sun)), their temperature and stellar luminosity are low and peaked in the red. We have re-examined what is known at present about the potential for a terrestrial planet forming within, or migrating into, the classic liquid-surface-water habitable zone close to an M dwarf star. Observations of protoplanetary disks suggest that planet-building materials are common around M dwarfs, but N-body simulations differ in their estimations of the likelihood of potentially habitable, wet planets that reside within their habitable zones, which are only about one-fifth to 1/50th of the width of that for a G star. Particularly in light of the claimed detection of the planets with masses as small as 5.5 and 7.5 M(Earth) orbiting M stars, there seems no reason to exclude the possibility of terrestrial planets. Tidally locked synchronous rotation within the narrow habitable zone does not necessarily lead to atmospheric collapse, and active stellar flaring may not be as much of an evolutionarily disadvantageous factor as has previously been supposed. We conclude that M dwarf stars may indeed be viable hosts for planets on which the origin and evolution of life can occur. A number of planetary processes such as cessation of geothermal activity or thermal and nonthermal atmospheric loss processes may limit the duration of planetary habitability to periods far shorter than the extreme lifetime of the M dwarf star. Nevertheless, it makes sense to include M dwarf stars in programs that seek to find habitable worlds and evidence of life. This paper presents the summary conclusions of an interdisciplinary workshop (http://mstars.seti.org) sponsored by the NASA Astrobiology Institute and convened at the SETI Institute.     

电推进航天器的特殊环境及其影响

文章介绍了应用离子和霍耳电推进系统在航天器周围产生的等离子体和电磁场等特殊环境,讨论了这些特殊环境对航天器各分系统或部件产生的溅射腐蚀、沉积污染、充放电、等离子体干扰、碰撞动力学扰动等影响效应,探讨了研究电推进与航天器相互作用效应的地面试验技术、空间飞行试验技术和模型分析技术,介绍了离子电推进系统与航天器相容性分析评价的技术要点。     

动力增升飞行LQG/LTR鲁棒控制器设计

研究线性高斯二次型回路传输恢复(LQG/LTR)鲁棒设计方法在动力增升阶段飞行/推进综合控制器设计中的应用问题,以带宽和Gibson准则作为基本的飞行品质指标,以奇异值作为鲁棒性指标,深入分析了基于LQG/LTR鲁棒控制的参数选择规律,包括姿态和速率指令的分配、前置滤波器的影响、扰动水平的预设、高频环节对系统鲁棒性和飞行品质的影响等问题.示例飞机构形的控制器设计结果表明:在LQG/LTR鲁棒飞行控制器设计过程中,适当选取响应类型参数和扰动水平因子,可以折衷飞机的飞行品质和鲁棒性能.