Integrating BDS and GPS for precise relative orbit determination of LEO formation flying

Low-Earth-Orbit(LEO) formation-flying satellites have been widely applied in many kinds of space geodesy. Precise Relative Orbit Determination(PROD) is an essential prerequisite for the LEO formation-flying satellites to complete their mission in space. The contribution of the BeiDou Navigation Satellite System(BDS) to the accuracy and reliability of PROD of LEO formation-flying satellites based on a Global Positioning System(GPS) is studied using a simulation method. Firstly, when BDS is added to GPS, the mean number of visible satellites increases from9.71 to 21.58. Secondly, the results show that the 3-Dimensional(3 D) accuracy of PROD, based on BDS-only, GPS-only and BDS + GPS, is 0.74 mm, 0.66 mm and 0.52 mm, respectively. When BDS co-works with GPS, the accuracy increases by 29.73%. Geostationary-Earth-Orbit(GEO) satellites and Inclined Geosynchronous-Orbit(IGSO) satellites are only distributed over the Asia-Pacific region; however, they could provide a global improvement to PROD. The difference in PROD results between the Asia-Pacific region and the non-Asia-Pacific region is not apparent. Furthermore, the value of the Ambiguity Dilution Of Precision(ADOP), based on BDS + GPS, decreases by 7.50% and 8.26%, respectively, compared with BDS-only and GPS-only. Finally, if the relative position between satellites is only a few kilometres, the effect of ephemeris errors on PROD could be ignored. However, for a several-hundred-kilometre separation of the LEO satellites, the SingleDifference(SD) ephemeris errors of GEO satellites would be on the order of centimetres. The experimental results show that when IGSO satellites and Medium-Earth-Orbit(MEO) satellites co-work with GEO satellites, the accuracy decreases by 17.02%.     

调温热沉换热系统仿真设计与应用

调温热沉具有操作简单,经济性好,降温速率快,对试验件无遮挡等优点,因此,在部组件级热真空试验中具有越来越重要的地位和意义。对于调温热沉的设计,本文中通过采用基于M文件表述的S函数程序和状态空间描述的分布参数模型用于系统仿真,从而得出载冷剂、试验件、热沉三者之间的温度动态关系。继而得到热沉温度控制方案中控制参数的影响条件以及调温热沉设计方案中载冷剂的温度和流量的数据。     

“九树十行”问题的几种栽法

本文从高等几何的Ｐａｐｐｕｓ定量入手，探讨了“把九棵树栽成十行，并使每行拾有三棵树”这样一个趣味问题的几种栽法。     

飞机结构的动强度问题研究与分析

首先分析了飞机在使用过程中遇到的振动和冲击及其对飞机结构可能造成的危害,再介绍了结构动强度设计的必要性,然后阐述了结构动强度的设计内容和设计方法.最后,结合实例分析了动强度设计的一般流程,并进行了小结.     

虹桥机场近距平行跑道仪表运行方式研究

针对虹桥机场近距平行跑道,以实现跑道系统最大容量为目标,综合考虑两个航站楼的布局情况,依据民航局有关运行规则,系统研究近距平行跑道的仪表运行方式,分析不同跑道运行方式下航站楼航班流量分布比例与近距平行跑道理论容量之间的函数关系,提出具有实际可操作性且适合虹桥机场近距平行跑道的最佳运行方式。     

Z连续偏序集P上σ~Z(P)的Soberity

Sober空间是介于T0 空间与T2 空间之间又完全独立于T1 空间的一类拓扑空间 ,本文基于拓扑σZ(P) ,证明了Z 连续偏序集P上的拓扑σZ(P)当σD(P)≤σ(P)时是Sober空间     

直流电压比率信号变换ARINC429数据信号的方案研究

研制适配器是实现机载设备之间信号交联的一种有效途径。在某大型系统中需要将直流电压比率信号变换为ARINC429数据信号,本文在简单分析输入输出信号特性的基础上,对信号变换的组成模块以及各功能模块的实现方案进行了论述。     

The morphology and velocity field of the large flare on the solar disc on July 14, 1980

The active region morphology and the features of solar radio bursts and sight-line velocity distribution of a flare of Importance 3B on the solar disc (AR 2562) on 1980 July 14 are introduced in this article.