Strategy to search fragments from breakups in GEO

This paper proposes a strategy to search fragments from breakups in the Geosynchronous Earth Orbit (GEO) region based upon population prediction and motion prediction by means of ground-based optical observations. Breakup fragments have uncertainties in the states such as their position and motion, or even in their existence. Population prediction and motion prediction resolve those uncertainties. Population prediction evaluates the time-averaged distribution of fragments, whose position at a given time is unknown, in the celestial sphere. Motion prediction evaluates the expected motion of fragments appeared in image series acquired by a telescope’s CCD camera. This paper logically describes procedures of the search strategy, and provides mathematical expressions of population prediction and motion prediction. This paper also validates the search strategy via actual observations, in which a confirmed breakup in the GEO region is selected as a target. It is concluded that the proposed strategy is valid even for searching uncataloged fragments from breakups in the GEO region.     

Shape and motion estimate of LEO debris using light curves

We have derived a tri-axial ellipsoidal model of an LEO object, a Cosmos 2082 rocket body, including its rotational axis direction, rotation period, precession, and a compositional parameter, using only light curve data from an optical telescope. The brightness of the object was monitored for two days and least-squares fitting was used to determine these values. The derived axial ratios are 100:18:18, the coordinates of the rotational axis direction on the celestial sphere are R.A. = 305.8° and Dec. = 2.6°, and its observed average rotation period is 41 s. When precession is considered, its amplitude and precession period are 30.5° and 29.4 min. These results show that optical light curve data are sufficient to determine the shapes and the motions of LEO objects.     

Object image linking of earth orbiting objects in the presence of cosmics

In survey series of unknown Earth orbiting objects, no a priori orbital elements are available. In surveys of wide field telescopes possibly many non-resolved object images are present on the single frames of the series. Reliable methods have to be found to associate the object images stemming from the same object with each other, so-called linking. The presence of cosmic ray events, so-called Cosmics, complicates reliable linking of non-resolved images. The tracklets of object images allow to extract exact positions for a first orbit determination.     

现代酒店客房服务中存在的问题及对策

为有效提高酒店客房的服务质量。通过实地调查研究,发现现代酒店客房服务中存在的主要问题,并分析其原因,提出解决方法。这对酒店的可持续发展至关重要,有助于酒店形成人性化的服务特色,增加其市场竞争力和旅游吸引力。     

飞机价值最大化准则下的工程评估

在分析了航空公司工程评估面临的问题和难点的基础上,提出了飞机价值最大化的工程评估准则,建立了在这一准则下的工程评估体系,同时将实物期权理论引入了基于飞机价值最大化准则的工程评估,以实物期权价值计算方法替代了传统的净现值方法.     

Image Quality assessment for Chang＇E-1 IIM 2C Data

嫦娥一号干涉成像光谱仪（IIM）获取的多波段图像数据对于月表矿物成分反演具有重要意义.从目视质量、客观参数、几何配准精度、图像质量随时间的变化情况等方面对IIM 2C级的多波段图像数据质量进行了评价.结果显示,其两端波段范围的图像质量较差,不能有效识别月表单元,中间波段图像质量较好;自然色图像显示IIM数据存在明显的横向色调不均一性.利用图像的客观评价指标（辐射精度、清晰度、信息量）将干涉成像光谱仪图像数据与美国Clementine UV-VIS多光谱图像数据进行对比分析,结果表明,IIM数据清晰度好于ClementineUV-VIS,而在方差和信息量上弱于Clementine UV-VIS.将IIM图像数据与Clementine多光谱数据统一到相同的空间分辨率,进行配准精度评价,其最大控制点配准误差为0.63 pixel.此外,还对时间跨度两个月覆盖月表同一区域的IIM图像数据从辐射精度、信息量和清晰度方面进行了评价.     

一种行星安全着陆点综合评估方法

随着精确着陆技术的发展,探测器在行星表面可到达的地区形貌状况越来越复杂。为了保障着陆的安全性,在下降过程中探测器需要结合敏感器信息对视野范围内的着陆区形貌进行评估分析,从而选取出最适宜着陆的地区。针对这一问题,本文提出一种行星安全着陆点选取思路,并设计出着陆点选取的参考指标,通过对形貌以及燃耗的评估,实时选取安全着陆点。MATLAB仿真结果表明,针对快速选取过程和遍历选取过程,该方法均能够在两种过程中有效选取出满足要求的着陆点,从而提高了任务的成功率与安全性。     

基于优化信任评估的Ad Hoc安全路由协议

针对Ad Hoc网络中自私节点造成的攻击问题,提出了一种基于信任评估的Ad Hoc安全路由协议TEAR。该协议在节点行为信任评估方案的基础上,通过使用链路信任值和路径信任值表示节点和路径的可信度,同时,在链路信任值计算时,引入了基于公共邻居节点的间接信任评估方法和可变时间窗机制,保证了信任值计算的准确性和实效性;协议中每个节点维护一张信任表,并重新定义了路由请求和路由回复消息格式,实现了安全路径的快速选择。使用NS2进行模拟验证,又与AODV以及基于固定时间窗信任评估的安全路由协议TA-AODV进行性能对比。结果表明,改进的信任评估方案具有更好的性能,采用该方案的安全路由协议能较快地发现自私节点,并准确选择安全路径,提高了Ad Hoc网络性能。      

变速变姿态下飞机燃油体积解算技术

为准确测量飞机不规则油箱内的燃油体积,在传统的查表插值法基础上,提出了基于等效传感器的自适应步长切割法（ASCM）,用于建立燃油质量特性数据库,通过引入等效传感器概念,实现了不同姿态下多传感器的信息融合;该方法根据切片截面积的变化率调整切割步长,从而减小了燃油体积解算时的插值误差;利用多传感器的输出值实现了燃油平面的最小二乘（LMS）拟合,当有效传感器较少时,再结合等效燃油平面姿态角拟合燃油平面,消除了加速度对燃油平面的影响;对传统的三维查表插值法进行改进,减小了由于燃油平面姿态角插值引起的误差。基于UG二次开发,设计了燃油体积解算平台。实际油箱CAD仿真验证结果表明:该方法所建的数据库数据规模小,燃油解算速度快,实现了加速度和姿态误差修正,并减小了差值误差,进一步提高了燃油的测量精度。      

北斗RDSS用户机测试系统关键技术研究

为了实现对北斗RDSS用户机检测的需求,研制了专用测试系统。介绍北斗RDSS用户机测试系统的基本组成和工作原理,分析了测试系统研制涉及到的部分关键技术：系统建模仿真、RDSS出站信号模拟、RDSS入站信号接收、入站信号质量分析等,最后列举了所研制的测试系统到达的主要技术指标。