北斗卫星通信导航信号激励器的方案设计和应用

根据北斗卫星系统工作原理,提出了北斗卫星通信导航信号激励器的方案设计和在直升机型号设计中的应用。该激励器具有模拟北斗卫星通信导航信号的功能,其作用是在航电系统地面综合联试中,为机载北斗接收机和组合导航系统提供激励信号。     

考虑卫星轨道运动和像移影响的星敏感器星图模拟方法

星图模拟技术是星图识别算法和星敏感器性能测试的基础.提出一种新的高精度星图模拟方法.该方法分为三个步骤:首先,利用两行轨道数据(TLE,Two-Line Orbital Element)与简化常规/深空扰动的近似解模型(SGP4/SDP4)计算出卫星在轨运行参数,进而获得卫星姿态矩阵;然后,根据星敏感器的方位和俯仰角度,确定星敏感器视场中的导航星及星敏感器安装矩阵,利用小孔成像模型,获得导航星在星敏感器成像面的投影位置;最后,为更准确模拟实际星像点的灰度扩散,在考虑卫星运动引起的恒星像移的基础上,按照二维高斯分布规律置灰度值来模拟星像点像素.在此基础上,还详细分析了不同曝光时间下,恒星像移对恒星位置测量的影响.     

一种适用于小推力轨控发动机“二次变轨”机动突防方案

针对突防发动机轨控推力较小,难以产生在拦截器末制导段内成功突防所需的机动过载的实际情况,提出避开拦截器机动性能最强的末制导段,而选择在拦截器自由飞行段和末制导结束后实施“二次机动变轨”的突防方案,旨在解决弹道中段机动突防方案的有效性问题.建立了推力方向、推力持续时间等轨控发动机主要控制参数的优化规划模型,提供了基于遗传...     

基于解析法的用户差分距离误差解算方法(英文)

为了进一步增强星基导航系统的完好性性能,提出了一种基于解析法的用户差分距离误差计算方法。文中首先介绍了卫星时钟和星历改正数的计算方法,认为计算用户差分距离误差的关键是查找卫星服务区域内的最差用户位置。通过变换卫星时钟和星历误差协方差矩阵,将查找最差用户位置变换成一个解析几何问题,通过数学推导得出最差用户位置的解析式,进而求解用户差分距离误差。通过计算机仿真对比了解析法和遍历法之间的性能差异,结果表明:解析法的正确性由遍历法得到了验证,解析法可以减少90%的运行时间并且具有更低的计算复杂度,便于工程实现。     

Hyper Heuristic Approach for Design and Optimization of Satellite Launch Vehicle

Satellite launch vehicle lies at the cross-road of multiple challenging technologies and its design and optimization present a typical example of multidisciplinary design and optimization(MDO) process.The complexity of problem demands highly effi-cient and effective algorithm that can optimize the design.Hyper heuristic approach(HHA) based on meta-heuristics is applied to the optimization of air launched satellite launch vehicle(ASLV).A non-learning random function(NLRF) is proposed to con-trol low-level meta-heuristics(LLMHs) that increases certainty of global solution,an essential ingredient required in product conceptual design phase of aerospace systems.Comprehensive empirical study is performed to evaluate the performance advan-tages of proposed approach over popular non-gradient based optimization methods.Design of ASLV encompasses aerodynamics,propulsion,structure,stages layout,mass distribution,and trajectory modules connected by multidisciplinary feasible design approach.This approach formulates explicit system-level goals and then forwards the design optimization process entirely over to optimizer.This distinctive approach for launch vehicle system design relieves engineers from tedious,iterative task and en-ables them to improve their component level models.Mass is an impetus on vehicle performance and cost,and so it is considered as the core of vehicle design process.Therefore,gross launch mass is to be minimized in HHA.     

Impact of covariance information of kinematic positions on orbit reconstruction and gravity field recovery

Gravity missions are equipped with onboard Global Positioning System (GPS) receivers for precise orbit determination (POD) and for the extraction of the long wavelength part of the Earth’s gravity field. As positions of low Earth orbiters (LEOs) may be determined from GPS measurements at each observation epoch by geometric means only, it is attractive to derive such kinematic positions in a first step and to use them in a second step as pseudo-observations for gravity field determination. The drawback of not directly using the original GPS measurements is, however, that kinematic positions are correlated due to the ambiguities in the GPS carrier phase observations, which in principle requires covariance information be taken into account. We use GRACE data to show that dynamic or reduced-dynamic orbit parameters are not optimally reconstructed from kinematic positions when only taking epoch-wise covariance information into account, but that essentially the same orbit quality can be achieved as when directly using the GPS measurements, if correlations in time are taken into account over sufficiently long intervals. For orbit reconstruction covariances have to be considered up to one revolution period to avoid ambiguity-induced variations of kinematic positions being erroneously interpreted as orbital variations. For gravity field recovery the advantage is, however, not very pronounced.     

基于RPC模型区域网平差技术的立体影像DSM提取

研究了利用卫星立体影像中提供的有理多项式系数(RPC)参数,采用基于RPC模型的区域网平差技术提取数字表面模型(DSM)的方法.研究结果表明,该方法提取的DSM效果较好.与Google Earth影像比较,中误差(RMSE)为6.122m,误差在8m以内的占参考点总数的80%,10m以上的占12%,最大误差为15.30...     

卫星遥感数据在城乡规划动态监测中的应用

概述了城乡规划动态监测对卫星遥感数据的要求,说明了卫星遥感影像数据应用于城乡规划动态监测的技术原理、工作流程及工作任务。以相关监测城市为例,阐述了2009-2010年我国36个城市建设用地规模、城市四线强制性内容等变化情况。监测成果说明,应用卫星遥感数据是城乡规划动态监测的有效手段。     

基于最大信噪比的带噪测控信号分离算法

在实际卫星测控信号侦察中,混合副载波信号分离比较困难,且耗时较长.为此,提出一种基于小波变换和最大信噪比的副载波盲分离算法.先利用小波阈值算法对混合带噪信号进行消噪处理,然后采用基于最大信噪比的盲分离算法对消噪后的信号实施分离,最后得到测控副载波信号的估计.MATALAB仿真结果表明,该算法计算复杂度低,耗时短,能够较...     

敏捷遥感卫星工作模式研究

综述了国外商业遥感卫星发展情况,归纳总结了高分辨率商业卫星的主要技术指标和特点。在充分调研国外敏捷遥感卫星的基础上,从成像目标需求、分辨率与幅宽关系、立体成像三方面总结出此类卫星的技术特点,阐述了发展敏捷遥感卫星的重要意义和作用,并深入分析了实现姿态敏捷控制的技术途径。利用姿态的敏捷控制能力,研究提出了多点目标成像、立体成像、宽幅拼接成像、动态扫描成像等4种典型工作模式,完成了敏捷卫星主要工作模式的分析与设计,并基于此工作模式要求,提出了敏捷卫星工程实现的技术途径。