基于STK的卫星系统设计优化研究

随着小卫星技术的发展,卫星系统的结构和功能也越来越复杂。为了降低卫星系统的造价,提高卫星系统的性能,需要对卫星系统进行设计优化。该文针对目前通用设计软件的不足,提出在STK和ModelCenter的基础上。开发卫星系统设计优化平台,详细阐述了基于STK仿真环境的卫星系统设计优化过程。为实现卫星系统的设计优化,应在任务分析的基础上定义STK场景,确定卫星系统的性能评价指标和设计变量,对设计变量进行敏感性分析,选择关键的设计变最,确定优化目标函数和约束条件并进行优化求解。最后给出了一个卫星系统设计优化的应用实例。     

卫星通信网的建模与仿真

卫星通信网是一个规模大、造价高的复杂通信系统,计算机仿真技术作为一种辅助手段具有非常重要的作用。通过仿真,可以简化设计过程,缩短设计周期,避免设计的盲目性,从而节省大量的人力物力。着重介绍了在网络仿真软件OPNET上如何建立一个基于话音业务的ALOHA接入方式的卫星通信网模型,并对该模型进行了仿真。     

CFOSAT散射计几何定位验证与精度初步评估

采用STK软件对中法海洋卫星（CFOSAT）散射计几何定位算法进行了验证。针对CFOSAT散射计扇形波束扫描观测体制,分别就扇形波束扫描散射计几何定位原型算法、包含天线安装误差的完整几何定位算法利用STK进行了详细验证。结果表明了CFOSAT扇形波束散射计几何定位算法的准确性,与STK几何定位结果偏差在100 m以内。在此基础上,结合有源定标器实验数据,对CFOSAT实际观测数据几何定位参数进行了校正,给出了CFOSAT散射计几何定位精度的初步评估。     

真实自然地表的红外辐射特性研究

采用特定算法从全球遥感卫星数据库中提取局部地区自然地表的高度信息和地表覆盖类型,结合地表几何结构生成技术和地面红外辐射理论模型,充分利用先验知识研究了国内的喀什、嫩江和衢州三地的地表组分温度及其红外辐射特征。给出的方案为地表组分温度的反演提供了参考依据,同时也大大提高了遥感信息的利用率。     

碳纤维复合材料卫星天线的研制

通过对不同模量碳纤维的选择，研制了碳纤维复合材料卫星天线，经过机械性能、电性能和空间环境等试验考核，表明：这种新型复合材料卫星天线在卫星减重方面与传统铝合金天线相比具有很大的优势。     

Contributions of meteorology to the phenology of cyanobacterial blooms: implications for future climate change

Cyanobacterial blooms are often a result of eutrophication. Recently, however, their expansion has also been found to be associated with changes in climate. To elucidate the effects of climatic variables on the expansion of cyanobacterial blooms in Taihu, China, we analyzed the relationships between climatic variables and bloom events which were retrieved by satellite images. We then assessed the contribution of each climate variable to the phenology of blooms using multiple regression models. Our study demonstrates that retrieving ecological information from satellite images is meritorious for large-scale and long-term ecological research in freshwater ecosystems. Our results show that the phenological changes of blooms at an inter-annual scale are strongly linked to climate in Taihu during the past 23 yr. Cyanobacterial blooms occur earlier and last longer with the increase of temperature, sunshine hours, and global radiation and the decrease of wind speed. Furthermore, the duration increases when the daily averages of maximum, mean, and minimum temperature each exceed 20.3 °C, 16.7 °C, and 13.7 °C, respectively. Among these factors, sunshine hours and wind speed are the primary contributors to the onset of the blooms, explaining 84.6% of their variability over the past 23 yr. These factors are also good predictors of the variability in the duration of annual blooms and determined 58.9% of the variability in this parameter. Our results indicate that when nutrients are in sufficiently high quantities to sustain the formation of cyanobacterial blooms, climatic variables become crucial in predicting cyanobacterial bloom events. Climate changes should be considered when we evaluate how much the amount of nutrients should be reduced in Taihu for lake management.     

分布式天基空间监视雷达编队构形

为克服地基观测系统时空监视能力的限制,提出分布式天基空间监视雷达编队的定位原理,并在平均定位误差最小的意义下对三星编队构形进行设计。其主雷达采用收发的工作方式,而2颗辅助雷达只进行接收。三星的几何布局在轨道运行过程中为动态变化,变化过程由三星构形决定。     

不同载噪比条件下误码性能测试分析

基于IDR／IBS体制,从诸多参数的概念入手,分析卫星通信中栽噪比、信噪比与误码率的关系,以及如何利用频谱分析仪准确测量接收卫星信号的载噪比。测试分析结果表明：不能为降低误码率而刻意提高（C0＋N0）／N0,必须经过认真的测试调整,寻求最佳值。     

一种基于GEO/MEO星层组网的卫星网络抗毁路由研究

提出一种新的基于GEO/MEO星层组网的抗毁路由算法（DRRA）,基于分群管理、群首备份、链路冗余、链路修补的星座结构.在基于卫星移动的动态卫星网络中,在数据包路由抗毁、数据包路由最短延时等方面具有优势.这主要在于：①在充分考虑该卫星网络结构特点的基础上采用卫星分群管理和群首备份机制,以减少网络中冗余信息的流动和对特定中心节点的依赖;②在充分考虑卫星网络运行环境复杂与恶劣的基础上采用星间链路冗余、星间链路修补方案,以降低网络中星间链路失效和/或卫星节点失效对整个卫星网络通信性能的影响.     

A band-ratio algorithm for retrieving open-lake chlorophyll values from satellite observations of the Great Lakes

The U.S. Environmental Protection Agency's Great Lakes National Program Office (GLNPO) has collected water quality data from the five Great Lakes annually since 1993. We used the GLNPO observations made since 2002 along with coincident measurements made by the Sea-viewing Wide Field-of-View Sensor (SeaWiFS) and the Moderate-resolution Imaging Spectroradiometer (MODIS) to develop a new band-ratio algorithm for estimating chlorophyll concentrations in the Great Lakes from satellite observations. The new algorithm is based on a third-order polynomial model using the same maximum band ratios employed in the standard NASA algorithms (OC4 for SeaWiFS and OC3M for MODIS). The sensor-specific coefficients for the new algorithm were obtained by fitting the relationship to several hundred matched field and satellite observations. Although there are some seasonal variations in some lakes, the relationship between the observed chlorophyll values and those modeled using the new coefficients is fairly stable from lake to lake and across years. The accuracy of the satellite chlorophyll estimates derived from the new algorithm was improved substantially relative both to the standard NASA retrievals and to previously published algorithms tuned to individual lakes. Monte-Carlo fits to randomly selected subsets of the observations allowed us to estimate the uncertainty associated with the retrievals purely as a function of the satellite data. Our results provide, for the first time, a single simple band ratio method for retrieving chlorophyll concentrations in the offshore “open” waters of the Great Lakes from satellite observations.