低轨导航星座增强BDS精密单点定位技术验证CSCD

首先介绍了低轨增强北斗精密单点定位(PPP)的观测模型、参数估计与数据处理策略。然后对低轨导航增强仿真验证系统及误差仿真配置进行了说明,基于验证系统仿真了全球20个监测站的北斗及低轨导航数据,并通过单北斗及低轨增强北斗静态PPP试验,给出了低轨增强北斗的高精度定位测试评估结果。结果表明,加入150颗低轨卫星观测量后,20个测站PPP精度收敛到10cm之内只需约1min;低轨增强北斗实现静态收敛后,定位精度东方向均值为1.5cm,北方向均值为0.3cm,高程方向均值为2.2cm。相较于北斗单独精密定位,20个监测站收敛后组合定位精度从5cm左右提升到3cm左右。加入低轨卫星可大大加快PPP收敛速度,提升定位精度,验证了低轨卫星在增强PPP精度和收敛速度上的优越性,同时仿真验证系统可支持全链路闭环仿真验证。     

低轨星座传感器资源实时调度方法

针对低轨星座传感器资源调度问题,提出了一种基于几何精度衰减因子（GDOP）和目标位置估计误差椭球的调度方法,该方法综合考虑了目标的静态、动态定位因素,优先选择卫星目标视线垂直于误差椭球长轴的传感器资源对目标进行跟踪。仿真结果表明,与已有的仅考虑GDOP的调度方法相比,该方法既节省了传感器资源,又提高了目标的跟踪精度。     

区域覆盖低轨卫星移动通信系统星座优化设计

针对区域覆盖低轨卫星移动通信系统星座,提出了一种改进遗传算法(GA)的优化设计。根据改进的区域覆盖星座模型,采用可变维数优化的整数与实数混合的染色体编码。给出了算法步骤。某区域覆盖低轨卫星移动通信系统星座优化设计算例结果显示了该算法的有效性。     

低轨对地观测卫星凝视成像仪探讨

文章介绍了典型空间信息获取方式及特点，阐述了低轨对地观测卫星凝视成像面临的问题及解决对策，对两种低轨对地观测卫星凝视成像仪及其应用进行了探讨。     

Comparison of the CHAMP radio occultation data with the Canadian advanced digital ionosonde in the Polar Regions

In this paper we present the results of the comparison of the retrieved electron density profiles of the Ionospheric Radio Occultation (IRO) experiment on board CHAMP (CHAllenging Minisatellite Payload), with the ground ionosonde profiles for the Polar Regions. IRO retrieved electron density profiles from CHAMP are compared with Canadian Advanced Digital Ionosonde (CADI) measurements at two vertical sounding stations well within the Polar Cap, Eureka (geog. 80°13′ N; 86°11′ W) and Resolute Bay (geog. 74°41′ N; 94°54′ W). We compared the ionospheric parameters such as the peak electron density of the F-layer (NmF₂) and the peak height of the F-layer (h_mF₂) for a 3-year period, 2004–2006. CHAMP derived NmF₂ shows reasonable agreement with the ionosonde retrieved NmF₂ for both the stations (0.76 and 0.71 correlation coefficient, for Eureka and Resolute Bay, respectively) whereas the h_mF₂ agreement is not that acceptable (0.25 and 0.37 correlation coefficient, respectively). The h_mF₂ from vertical sounding showed less spread than the CHAMP h_mF₂.     

基于低轨移动星座的高速星载路由器设计

随着地面网络流量不断增长,实现星地一体化要求星间网络能够提供基于IP的大流量数据传输。而星载路由器作为连通星间网络的关键设备,其转发速率和服务质量等指标决定了整个星间网络的吞吐量和时效性。考虑到现有星载路由器吞吐量低的现状,提出一种适用于低轨移动通信星座的高速星载路由器设计方案,在基于拓扑快照的路由基础上补充3层动态路由,在保证交换速率的同时减少网络故障导致的丢包,实现“一次路由,多次交换”。采用共享内存式的交换存储单元,利用Spacewire和Serdes高速接口单元,理论上星间数据吞吐量能够达到最高51Gbit/s,且支持IP数据传输,为与地面网络的融合奠定基础。     

一种基于反向探测的低轨星座路由算法

针对低轨卫星星座通信系统动态拓扑结构的特点,提出了一种基于反向探测的路由算法（Reverse Detection Based Routing,RDBR）,采用分布式实现且具有极低的运算复杂度,适合于星上实时计算,对于提高星座网络的自主运行能力具有重要意义。与快照序列（Sequent Snap Shots,SSS）算法的对比分析和仿真表明,RDBR算法以有限的信令开销取得的路由性能优于60s快照序列算法。
     

Simulation study for the determination of the lunar gravity field from PRARE-L tracking onboard the German LEO mission

A simulation study has been performed at GFZ Potsdam, which shows the anticipated improvement of the lunar gravity field model with respect to current (LP150Q model) or near-future (SELENE) knowledge in the framework of the planned German Lunar Explorations Orbiter (LEO) mission, based on PRARE-L (Precise Range And Range-rate Equipment – Lunar version) Satellite-to-Satellite (SST) and Satellite-Earth-Satellite (SEST) tracking observations. It is shown that the global mean error of the lunar gravity field can be reduced to less than 0.1 mGal at a spatial resolution of 50 km. In the spectral domain, this means a factor of 10 (long wavelengths) and some 100 (mid to short wavelengths) improvement as compared to predictions for SELENE or a factor of 1000 with respect to LP150Q. Furthermore, a higher spatial resolution of up to 28 km seems feasible and would correspond to a factor of 2–3 improvement of SELENE results. Moreover, PRARE-L is expected to derive the low-degree coefficients of the lunar gravity field with unprecedented accuracy. Considering long mission duration (at least 1 year is planned) this would allow for the first time a precise direct determination of the low-degree tidal Love numbers of the Moon and, in combination with high precision SEST, would provide an experimental basis to study relativistic effects such as the periselenium advance in the Earth–Moon system.     

一种低轨道卫星服务区域分配的优化算法

在提供Internet和其他通信服务方面,能够覆盖全球的低轨道卫星网络正变得愈加重要。如何根据地面业务的时空分布不均来设计合理、高效的卫星服务区域分配机制是一个重要的挑战。文章分析了传统机制下卫星网络承载能力和业务分布之间的失配问题,提出了服务区域分配优化问题的数学模型,并据此设计了一种星上实时算法。仿真结果表明,采用该算法后卫星网络业务分配不均衡程度有所减轻,阻塞概率大大降低,网络性能和容量得到了明显改善。     

基于信道特性的低轨卫星切换性能研究

在卫星与地面终端之间的星地链路中,存在复杂多变的信道环境,这些因素对系统的切换性能有着重要影响。文章首先建立星地信道模型,并将此模型应用于切换过程,通过仿真得到信道特性对于切换性能的具体影响。