卫星天线热真空变形测量

针对在真空环境中进行高低温测量的难点和特点,提出了采用数字近景摄影测量技术在热真空中对卫星天线面板的高低温变形进行测量。成功地利用2台经过保护的专业像机组成双相机摄影测量系统,完成了天线热真空变形测量,解决了传统的测量手段无法在真空中进行测量的难题,型面变形测量精度达到0.1mm,满足了试验要求。     

Monitoring of the space system

We have performed monitoring of the space system that includes the Earth, the Moon, the Sun, and the GPS satellite group. We have discovered semi-diurnal and diurnal periodicities in the number of satellites detected as well as in the altitude, latitude and longitude by a GPS receiver. We have revealed tidal deformations related to changes in the Earth?s orientation with respect to the Moon and the Sun.     

Achievable debris orbit prediction accuracy using laser ranging data from a single station

Earlier studies have shown that an orbit prediction accuracy of 20 arc sec ground station pointing error for 1–2 day predictions was achievable for low Earth orbit (LEO) debris using two passes of debris laser ranging (DLR) data from a single station, separated by about 24 h. The accuracy was determined by comparing the predicted orbits with subsequent tracking data from the same station. This accuracy statement might be over-optimistic for other parts of orbit far away from the station. This paper presents the achievable orbit prediction accuracy using satellite laser ranging (SLR) data of Starlette and Larets under a similar data scenario as that of DLR. The SLR data is corrupted with random errors of 1 m standard deviation so that its accuracy is similar to that of DLR data. The accurate ILRS Consolidated Prediction Format orbits are used as reference to compute the orbit prediction errors. The study demonstrates that accuracy of 20 arc sec for 1–2 day predictions is achievable.     

Evaluation of three high-resolution satellite precipitation estimates: Potential for monsoon monitoring over Pakistan

Multi-sensor precipitation datasets including two products from the Tropical Rainfall Measuring Mission (TRMM) Multi-satellite Precipitation Analysis (TMPA) and estimates from Climate Prediction Center Morphing Technique (CMORPH) product were quantitatively evaluated to study the monsoon variability over Pakistan. Several statistical and graphical techniques are applied to illustrate the nonconformity of the three satellite products from the gauge observations. During the monsoon season (JAS), the three satellite precipitation products captures the intense precipitation well, all showing high correlation for high rain rates (>30 mm/day). The spatial and temporal satellite rainfall error variability shows a significant geo-topography dependent distribution, as all the three products overestimate over mountain ranges in the north and coastal region in the south parts of Indus basin. The TMPA-RT product tends to overestimate light rain rates (approximately 100%) and the bias is low for high rain rates (about ±20%). In general, daily comparisons from 2005 to 2010 show the best agreement between the TMPA-V7 research product and gauge observations with correlation coefficient values ranging from moderate (0.4) to high (0.8) over the spatial domain of Pakistan. The seasonal variation of rainfall frequency has large biases (100–140%) over high latitudes (36N) with complex terrain for daily, monsoon, and pre-monsoon comparisons. Relatively low uncertainties and errors (Bias ±25% and MAE 1–10 mm) were associated with the TMPA-RT product during the monsoon-dominated region (32–35N), thus demonstrating their potential use for developing an operational hydrological application of the satellite-based near real-time products in Pakistan for flood monitoring.     

基于人工神经网络的反射器型面精度预测

基于人工神经网络的预测方法,利用数量适当的有限元计算结果,建立人工神经网络模型,对反射器型面进行精度预测分析,得到在最小型面精度结果下的结构设计参数。计算结果显示训练好的神经网络模型能够较精确地预测格栅反射器的型面精度,节省计算时间,并且以型面精度最小为准则进行参数分析,能够指导反射器的结构设计。     

卫星与地面测控系统协调设计研究

卫星运行需要地面测控系统的支持.通过对某些卫星运行与地面测控系统支持方面的实际分析,总结其设计研制和协调中不足,研究卫星系统与地面测控系统的协调设计,并提出相应建议,为我国的卫星发展作一些借鉴.     

微波能量传输系统设计及试验

面向空间太阳能电站应用,进行了固态体制微波能量传输技术研究。针对能量传输波束扩散导致收集效率低的问题,研究了基于人工媒质理论设计的完美匹配层的能量接收整流表面,通过调节人工媒质单元的结构参数实现天线输出阻抗与整流电路输入阻抗的共轭匹配,同时抑制整流电路高次谐波,省去原有匹配及低通滤波器,简化电路结构、实现高效微波能量吸收与转换。以空间太阳能电站规定的波束中心传输微波功率密度限制作为能量接收整流表面设计的约束条件,设计能量接收整流表面,结合固态体制微波能量发射端,搭建5.8GHz小规模微波能量传输系统开展了地面试验验证,实测结果显示整流表面能量转换效率最高为57.7%。此次试验验证了先进的固态能量传输试验系统,为空间太阳能地面缩比试验及未来空间太阳能电站的建设提供了技术支撑。     

Yarkovsky-Schach effect on space debris motion

The Yarkovsky-Schach effect is a small perturbation affecting Earth satellites and space debris illuminated by the Sun. It was first applied to the orbit of LAGEOS satellites as an explanation of the residuals in orbital elements. In this work, we carry out several numerical integration tests taking into consideration various orbit and rotation parameters, in order to analyse this effect in a broader context. The semi-major axis variations remain small and depend on the spin axis attitude with respect to the Sun. We show that the force amplitude is maximised for orbits inclined with $i\approx$?20–30°. We also observe the influence on other orbital elements, notably on the orbit inclination. However, these effects are clearly observed only on long timescales; in our simulations, we propagated the orbits for 200?y. The Yarkovsky-Schach effect is thus confirmed to have a minuscule magnitude. It should be taken into account in studies requiring high-precision orbit determination, or on expanded timescales.     

卫星地面测控站的防雷技术

雷电是大气中带有大量电荷的雷云放电的结果,落地雷强大的雷电流可达数十至数百千安培。由于卫星测控站的天线通常是附近最高的建筑物,在雷雨季节容易招引雷电。文章在对卫星地面测控站的多起雷击事故进行调研统计的基础上,分析得出测控设备遭受雷击的原因,讨论了卫星地面测控站的防雷击理论和接地技术,提出测控站防雷击措施,主要包括等电位接地、等电位连接、机房电磁屏蔽、合理布线等。     

美国转型通信体系研究

2002年初,美国国防部发起了针对政府通信卫星的转型通信研究（TCS）,以加快具有先进技术水平的高级通信能力交付到战场的过程。同年年底成立了转型通信办公室（TCO）,同步、协调和指导美国转型通信体系（TCA）的开发。转型通信体系涉及美国众多政府机构,主要包括国防部、情报界和国家航空航天局。其目标是消除通信的限制,通过协调、有效地开发和部署空间和地面独立、兼容、互操作系统,构建未来20年政府空间通信体系。TCA文件至今已经发展了3个版本,经历了多次变动和改进。文章介绍了TCA的定义、目的、范围和组成,分析其发展演进过程,总结其经验教训,最后给出几点结论与启示。