通信卫星模拟器通用基础平台设计研究

卫星模拟器主要是对地面测控系统遥测接收和遥控指令发送的工作状态进行检查和验证,验证地面测控系统设备正确性,提高地面测控系统对卫星故障的应急处理能力等。本文从软件系统架构高度对不同卫星各分系统模型共有属性进行抽象提炼和设计研究,提高软件架构及模块的复用性、扩展性和维护性,通信卫星模拟器通用基础平台可同时验证不同卫星对地面测试系统的任务要求,使不同卫星模拟器的建设和地面系统测试支持可以纳入一个规范化、通用化的系统框架中。     

单颗导航卫星的轨道确定

讨论在导航星座只有一颗卫星时,不依赖于时间同步系统的卫星定轨策略和精度分析。采用历元间差分算法,在消除钟差的主项（低频）误差后,将伪距和相位数据转化为等价的积分Doppler数据,并对其建立测量模型。仿真分析表明,此时不需要知道钟差参数而定轨算法收敛。为进一步验证此定轨方案的可行性及其定轨精度,利用实测的GPS数据进行轨道确定计算,计算结果表明,采用历元间差分算法,利用国内观测台站3天弧段的观测资料对单颗GPS卫星进行定轨,其径向精度优于10m,利用其对国内定位用户的用户距离误差URE可达13．8m。     

航天器天基测控中心关键技术分析

天基测控模式是航天器测控发展的必然趋势.天基测控模式与地基测控模式有着本质的区别,如何实现天基测控是我国航天领域目前研究的重点课题之一.本文在分析天基测控技术和我国现有条件的基础上,提出了实现航天器天基测控的方法,分析研究了与航天器天基测控中心相关的关键技术。     

卫星初始轨道确定方法研究

卫星精密轨道确定过程实际上是通过求解轨道动力学微分方程组而对初始轨道不断改进的过程,因此,轨道确定的精度与速度不但依赖于求解微分方程组的具体算法,同样依赖于初始轨道的精度与准确性。针对多站测距/距离和数据,建立了一种轨道初值计算的几何方法,该方法集折射误差修正方法于一体,在进行观测数据折射误差修正的基础上,可以得到卫星在任意时刻的轨道初值。     

基于北斗卫星系统的频率标准源的设计与实现CSCD

在对北斗二代导航定位接收机输出的1PPS信号进行测试、分析、研究的基础上,采用数字滤波器滤波和电压的积分控制相结合的方法,滤除信号传输过程中的干扰,使其输出相对平稳的1PPS信号来驯服铷原子频标。研究北斗接收机驯服铷钟原子频标的模型,采用精密时间间隔测量、高精度数字比相、计算机自动控制等多种先进技术,完成对铷原子频标的跟踪控制,实现与星载铷钟同等精度的时频信号输出。研制了一套北斗接收机驯服铷原子频率标准源,该频率标准携带方便,性价比高,既可以为时统、通讯系统提供现场计量技术保障,又可以实现对原子频率标准的远程校准、核查。     

星间激光输能姿态指向自适应控制器设计

针对同轨道平面两星之间激光能量传输时的姿态指向控制问题,基于反步（Backstepping）法提出了一种自适应控制器设计方法。该方法先基于罗德里格参数（MRP）对卫星进行姿态描述;然后根据星间激光输能任务对姿态指向的特殊要求通过多个姿态矩阵的转换解算出了用户星期望姿态的表达式;之后基于Backstepping法,设计了自适应控制律,该控制律能解决控制输入有限和转动惯量不确定的问题,而且有效克服空间干扰力矩;最后通过Lyapunov稳定性定理证明了控制系统的稳定性。仿真结果显示,在约15s后,用户星的姿态误差和角速度误差收敛到0,并且角速度和控制力矩的值都在约束条件的范围内,说明文章设计的控制器不仅能够使用户星按最短路径调整到期望姿态,而且能够有效地抑制空间干扰力矩和解决转动惯量不确定的问题,并且通过合理地设计控制参数,可以在保证控制精度和速度情况下使控制输入满足约束条件。     

DEMETER and DMSP satellite observations of the disturbed H/O ratio caused by Earth’s seismic activity in the Sumatra area during December 2004

In the present paper, plasma probe data taken from DEMETER and DMSP-F15 satellites were used to study the ion density and temperature disturbances in the morning topside ionosphere, caused by seismic activity at low latitudes. French DEMETER (Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions) micro-satellite mission had been especially designed to provide global scale observations in the topside ionosphere over seismically active regions. Onboard the DEMETER satellite, the thermal plasma instrument called “Instrument Analyser de Plasma” (IAP) provides ion mass and densities, ion temperature, three component ion drift and ion density irregularities measurements. As a part of “Defense Meteorological Satellite Program”, DMSP-F15 satellite is on orbit operation since 1999. It provides ionospheric plasma diagnostics by means of the “Special Sensor-Ion, Electron and Scintillations” (SSIES-2) instrument. We examined few examples of possible seismic effects in the equatorial ionosphere, probably associated with seismic activity during December month in the area of Sumatra Island, including main shock of giant Sumatra event. It is found that the localized topside ionospheric disturbances appear close to the epicenters of certain earthquakes in the Sumatra region. In two cases, ion H⁺/O⁺ ratio rises more than one hour before the main shock, due to the O⁺ density decrease at the winter side of the geomagnetic equator, with longitudinally closest location to the epicenter of the earthquakes. These anomalous depletions in O⁺ density do exist in all cases of SSIES-2 data. Particularly for Sumatra main event, more than one hour after the main shock, we observe large-scale depletion in O⁺ density northward of the geomagnetic equator at winter side hemisphere. Associated with O⁺ depletion, ion temperature latitudinal profile around the geomagnetic equator shows enhanced asymmetry with minimum at the summer side and maximum in positive Ti deviation from mean value at the winter side. This disturbance lasted for more than three hours, later in time observed at the same place by IAP/DEMETER.     

Impact of four dimensional assimilation of satellite data on long-range simulations over the Indian region during monsoon 2006

A number of experiments were conducted to study the impact of updating model basic fields by satellite data (Quick Scatterometer (QSCAT) surface winds and Atmospheric Infrared Sounder (AIRS) temperature and humidity profiles) on long-range simulation during the Indian summer monsoon 2006. The Pennsylvania State University/National Center for Atmospheric Research (PSU/NCAR) mesoscale model version5 (MM5) and its four dimensional data assimilation (FDDA) technique was used for the numerical simulations. The spatial distribution and temporal variation in model simulated basic meteorological parameters and rainfall were verified against the observed fields from National Center for Environmental Prediction (NCEP) analysis and Tropical Rainfall Measuring Mission (TRMM), respectively. The overall analysis of the results from QSCAT surface wind assimilation as compared to control simulation (CNT; without the satellite data assimilation) suggest that a better representation of a single level wind field during model integration fail to make significant improvement in the model simulation both in the basic meteorological parameters and rainfall. The assimilation of temperature and humidity profiles from the AIRS during model integration significantly improved the rainfall prediction during monsoon period. It is found that the improvement in rainfall prediction is attributed to improved thermodynamics structure due to AIRS profile assimilation and the degree of improvement is more in temperature prediction as compared to humidity prediction. It is also found that the prediction over the regions, such as south west part of India and foothills of Himalaya, where a complex orography exists, is not significantly benefited from satellite data assimilation which highlights the need of improvement in the model in addition to a better representation of atmospheric state.     

月球表面粗糙度的分形表征

文中采用"嫦娥一号"卫星探测器返回的激光高程计的数据,从研究月球表面的分形特征出发,选取月球表面的湿海区域进行研究,通过对激光高度计的原始数据进行处理,并利用SPSS统计软件对这两组数据进行拟合得到最佳的拟合模型。结果指出:1)分维可以作为一个独立的表征参量来表征粗糙表面的平缓程度。2)由拟合结果图可知,对于月球表面的湿海区域,分维与粗糙度存在单调递增关系,即分维值越大,区域表面越粗糙,表面起伏变化也越剧烈;并通过分析得出湿海区域的地形起伏较大。3)通过分维值D与粗糙度之间的关系式,对于某区域的任意一段轮廓,可以通过计算分维值D得出该轮廓的粗糙度值。同样的,对任一粗糙度值,可以求出相应的分维值以及该轮廓的具体纬度值位置。4)对于月球表面的其他区域,同样可以得出他们之间的相关性,从而达到研究月表地貌演化过程的目的。     

北斗全球卫星导航系统境外星数据快速回传的路由优化方法

针对北斗全球卫星导航系统存在的全球布站不足问题,提出一种利用星间链路将境外星数据快速回传至境内的路由优化方法。首先描述地面站受限情况下的数据快速回传问题,明确传输路由的优化目标、生成规则、约束条件。然后提出基于遗传算法的时延最小数据传输路由优化策略。最后,对算法进行了验证。结果表明,在2个境内站条件下,北斗系统全星座最多2跳（6s内）完成数据传输,可满足境外数据快速回传的要求。