The enigma of small satellites for earth observation

Small satellites have captured a continuously increasing share of the market in the fields of science, technology and recently also in the telecommunications and Earth observation areas. User requirements and market opportunities for space based satellite systems for Earth observation products have grown substantially in the past decade. Criteria for the utilization of different classes of satellite systems (small and large) and analogies to developments in other areas, e.g. the telecommunications field are discussed. The end to end character of service and product oriented systems as key criteria for market success in the scientific, applications and commercial areas is underlined. Recent developments in the global change, the Earth observation applications and commercial sectors are reviewed and compared. Opportunities for small satellites in the field are related to technology advancements, cost reduction options, and progress in the state of the art in system design.     

卫星巡天扫描运控模式方法的研究

巡天扫描是天文卫星进行天体观测的基础，但是使用传统方法很难实现全天球覆盖，并且会遇到能源输出瓶颈。因此，针对天文卫星巡天扫描所遇到的问题，提出了使用Pareto遗传算法对卫星飞行任务进行智能规划的方法。该算法引入小生境方法来保证群体多样性，并使用基于排序的适应度分配方法来克服早熟收敛。该算法智能规划飞行任务，与仅依靠被动的分段式扫描方法相比，在扫描全天球的基础上，很好解决了能源输出的问题，还大大缩短了巡天扫描的时间。从仿真结果来看，该模型是十分有效的。     

实现给定传递函数的模拟电路中的静态问题

实现给定传递函数的模拟电路一般包含若干个运算放大器及电阻、电容等元器件。为了使电路正常工作,就要使运算放大器在输入信号的整个变化范围内,始终处于线性状态。本文从理论上对这一问题进行了分析,经实验证实是正确的,这一方法对于工程设计具有指导意义。     

Survey of mission evolution and flexibility in the Space Shuttle program

Given the diversity of missions it has accomplished and the myriad of adaptations it has undergone, the US Space Shuttle is widely regarded as a highly flexible space vehicle. With the Shuttle’s upcoming 2011 retirement, it is instructive to survey the history of this vehicle’s flexibility for the insights it can provide to the design and characterization of flexibility in future space systems. Data are presented on the evolution of mission requirements over time for 120 missions performed by the Space Shuttle over a period of some 27 years. Distinct trends in the time domain – as well as their causes – are identified and discussed, and early manifest plans from 1982 serve as a confirmation that these trends were not originally anticipated. Eight examples are then presented of engineering modifications that allowed the Shuttle to adapt and accommodate these requirement changes. Several additional instances of Shuttle flexibility are explored, such as post-Columbia disaster modification, upgrade programs and derived vehicles, and one case in which flexibility was inhibited by an early design decision.     

Gamma Astrometric Measurement Experiment (GAME) – Implementation and performance

The GAME mission concept is aimed at testing the General Relativity, through precise measurement of the gravitational deflection of light by the Sun, by means of an optimised telescope operating in the visible and launched in orbit on a small class satellite. We describe the proposed mission profile, the preliminary payload design and the expected performance. The targeted precision on the γ parameter of the PPN formulation of General Relativity is in the range 10⁻⁶ to 10⁻⁷. The measurement principle relies on the differential astrometric signature on the stellar positions. The instrument concept is based on a dual field, multiple aperture Fizeau interferometer, observing simultaneously two sky regions close to the solar limb. A beam combiner folds the telescope line of sight on two different directions on the sky, separated by a base angle of 4°. The diluted optics approach achieves an efficient rejection of the scattered solar radiation, while retaining an acceptable angular resolution on the science targets.     

多种示漏气体分析仪的研制

借鉴欧洲空间中心所用检漏仪的原理及主要技术措施，采用分子泵和机械泵的真空获得系统、钛升华泵和旁通阀真空维持系统、高灵敏的质谱分析系统，研制出了一次能检测出多个系统的高灵敏的多种示漏气体分析仪。文章介绍该分析仪的原理、设计方案、设计特点、设计计算。进行了性能测试，结果表明：该分析仪在大气环境条件下，最小可检测Ｈｅ，ＣＦ４的浓度小于５×１０－８，对Ｎｅ小于５×１０－７。     

一种多任务导航星座设计方法

在分析多任务导航星座中心任务和附加任务的基础上,用n 1重覆盖率评价星座对地面的覆盖性能,基于运筹图论对多任务星座设计及选星方案进行了研究。仿真结果表明,由该法确定的选星方案可满足多任务星座的使命要求。     

国外思想政治教育方法借鉴

国外思想政治教育的许多做法和经验值得我们学习和借鉴。通过对国外思想政治教育的研究,概述了渗透式和隐蔽式的教育方法、以活动为教育载体的方法、环境熏陶法、寓德于教,学科协调法、道德认知发展法、＂七结合＂和＂六顺＂的德育方法以及心理咨询法等方法,并对我国学校思想政治教育的经验与教训进行了宏观的理性思考。     

0—10V高稳定直流电压基准的研究

介绍一种0～10V可调直流电压基准的设计。该电压基准通过对电压平均技术和双通道脉宽调制分压技术的研究与应用，既可使用内部高稳定直流电压基准，也可外接高稳电压基准实现0V～10V直流电压的连续输出，保障了直流电压基准输出的连续性与稳定性，其10V输出稳定度指标优于2·10^-6／y（恒温条件下），可广泛用于高水平电压标准器的研制。     

一种分布式电动飞机螺旋桨滑流影响机理

提出了一种分布式电推进螺旋桨飞机，采用二阶精度求解RANS方程的k-ω SST （Shear-Stress-Transport）湍流模型，基于多参考系（MRF）方法，针对低速特性进行数值模拟，得到了分布式螺旋桨滑流效应对全机气动特性的影响规律，重点对螺旋桨后方速度场及机翼表面压力分布进行分析。结果表明有滑流状态增加了全机升力和阻力，升力系数最大增量超过65%，且升力增量随迎角的增加而增大，改善了失速性能，增加了低头力矩；螺旋桨旋转增加了周向速度，改变了径向速度分布，增加轴向速度，高能量螺旋桨滑流改变了机翼当地升阻力特性；螺旋桨桨叶向上旋转一侧气流受上洗影响而局部迎角增加，另一侧局部迎角降低，越靠近桨盘位置，受螺旋桨洗流带来的影响越大；螺旋桨的旋转方向对螺旋桨两侧的机翼表面压力分布有较大影响，尤其是翼尖螺旋桨对全机气动性能影响较大。