Submillimeter Wave Astronomy Satellite observations of Comet 9P/Tempel 1 and Deep Impact

On 4 July 2005 at 5:52 UT the Deep Impact mission successfully completed its goal to hit the nucleus of 9P/Tempel 1 with an impactor, forming a crater on the nucleus and ejecting material into the coma of the comet. NASA's Submillimeter Wave Astronomy Satellite (SWAS) observed the ₁₁₀-₁₀₁ ortho-water ground-state rotational transition in Comet 9P/Tempel 1 before, during, and after the impact. No excess emission from the impact was detected by SWAS and we derive an upper limit of 1.8×¹⁰⁷ kg on the water ice evaporated by the impact. However, the water production rate of the comet showed large natural variations of more than a factor of three during the weeks before and after the impact. Episodes of increased activity with alternated with periods with low outgassing (). We estimate that 9P/Tempel 1 vaporized a total of N∼4.5×¹⁰³⁴ water molecules (∼1.3×¹⁰⁹ kg) during June-September 2005. Our observations indicate that only a small fraction of the nucleus of Tempel 1 appears to be covered with active areas. Water vapor is expected to emanate predominantly from topographic features periodically facing the Sun as the comet rotates. We calculate that appreciable asymmetries of these features could lead to a spin-down or spin-up of the nucleus at observable rates.     

Perihelion motion of small irregular dust particles due to radiation forces

Perihelion motion, i.e. a secular change of longitude of perihelion, of interplanetary dust particles is investigated under the action of solar gravity and solar electromagnetic radiation. As for spherical particle [Kla?ka, J., 2004. Electromagnetic radiation and motion of a particle. Cel. Mech. Dynam. Astron. 89, 1-61]: (i) perihelion motion is of the order ( is heliocentric velocity of the meteoroid and c is the speed of light in vacuum), if a component of electromagnetic radiation acceleration is considered as a part of central acceleration; (ii) perihelion motion is of the first order in if the total electromagnetic radiation force is considered as a disturbing force. The new facts presented in this paper concern irregular dust particles. Detailed numerical calculations were performed for the grains ejected at aphelion of comet Encke. Perihelion motion for irregular interplanetary dust particles exists already in the first order in for both cases of central accelerations. Moreover, perihelion motion of irregular particles exhibits both positive and negative directions during the particle orbital motion. Irregularity of the grains causes not only perihelion motion, but also dispersion of the dust in various directions, also normal to the orbital plane of the parent body.     

1：10000地形图航摄成图内业质量控制方法研究

介绍了1∶10 000地形图航摄成图内业生产质量控制的方法,并以实际工作为依据,对该方法进行了详细阐述。同时,还介绍了元数据的生产和质量自动控制方法。     

基于动态阈值的HJ-1B图像云检测算法研究

针对环境与灾害监测预报小卫星星座1B星(HJ-1B)的传感器波段特征,通过对云检测阈值的年度波动性分析,提出了一种基于波谱标准差异常的“动态阈值云检测算法”.该算法的实现主要是采用图像配准、波段运算、线性回归和误差分析等方法,获取云异常区域,进而剔除图像中的云像元.研究结果表明,该算法可以很好地检测出不同时相、不同类型下垫面上空的云像元,为有效利用HJ-1B数据并提高其图像分类精度发挥作用.     

1：50000数据库的更新服务数据库系统设计与实现

1：50000数据库的更新工程数据库服务系统是以1：50000数据库更新成果为基础．建立了一个基于B／S结构的服务系统,满足更新数据快速发布、浏览、应急服务等需求。本文介绍了陔系统的设计思想、系统总体架构、数据库设计与建库、软件功能设计与实现,为其他地理信息数据系统建设提供借豁。     

基于GIS交通网络的室内3维网络模型研究

在2维交通网络逻辑数据模型基础上,讨论了概念化的楼层网络,进行了室内连通的3维网络模型的研究。基于ArcGIS的交通网络模型建立了试验区的室内3维网络模型．并给出分析结果,该方法为室内3维网络模型研究提供了技术支持。     

基于最大似然法和SVM法的太湖流域HJ-1B影像分类

以太湖流域作为研究对象,基于环境减灾卫星HJ-1B影像数据,比较利用最大似然法和支持向量机法进行土地利用/覆盖分类的效果。结果显示,SVM法在总体分类精度和Kappa系数上较传统最大似然法有所提高。SVM分类方法对于有限样本的分类表现出优越的性能,改善了传统分类方法的局限性,具有很大的应用潜力。     

“天绘一号”卫星工程建设与应用

概括“天绘一号”卫星工程的建设历程和卫星系统的使命任务;介绍了卫星系统和相机载荷的能力与技术参数;重点阐述了“天绘一号”卫星无地面控制条件下的摄影测量关键技术, 包括LMCCD相机体制、航天摄影测量相机参数在轨标定技术以及无地面控制点条件的三线阵EFP影像平差技术等的运用, 通过工程实践, 达到了工程技术指标要求;最后介绍数据应用情况, 提出“天绘一号”卫星的发展设想, 为了解“天绘一号”卫星工程提供了基本参考。     

“天绘一号”01星立体影像定位精度检测

利用多个测区的样本数据和大量的野外实测GPS控制点, 进行“天绘一号”01星立体影像无控制点、不同控制条件下的定位精度检测, 结果表明在无控制点定位时平面精度优于10 m, 高程精度优于6 m, 控制点定向时的检查点平面精度优于9 m, 高程精度优于3 m, 完全满足1:50000比例尺成图精度要求。     

“天绘一号”卫星在轨辐射定标方法

在轨辐射定标包括相对辐射定标和绝对辐射定标, 它是提高遥感数据定量化精度的关键步骤和重要方法。本文阐述了基于均匀场地分区综合的相对辐射定标方法、基于反照率的绝对辐射定标方法及其基本原理, 并首次将其应用于“天绘一号”卫星上的高分辨、多光谱和三线阵相机的辐射定标中。研究结果表明, 相对辐射定标过程去除了卫星图像的条带噪声, 且保存了图像细节;然后, 使用反照率基法, 通过在敦煌场地铺设灰阶靶标, 测量卫星过顶时的地物目标反射率光谱和大气信息, 对“天绘一号”卫星传感器进行了绝对辐射定标;最后, 使用辐射定标结果来反演地物反射率, 与实测的地物反射率相比误差小于5%, 验证了在轨辐射定标系数的有效性。