基于嫦娥一号卫星激光测高观测的月球地形模型CLTM-s01

利用中国第一颗探月卫星嫦娥一号第一次正飞阶段获取的约300多万个有效激光测高数据点, 得到了改进的360阶次球谐函数展开月球全球地形模型CLTM-s01(Chang’E-1 Lunar Topography Model s01). 该模型以月球质心为参考球心, 以月球平均半径1738 km正球面为参考基准, 径向高程测量精度约为31 m, 沿赤道区域空间分辨率约为0.25°(7~8 km). 该模型首次利用激光测高数据得到月球极区高精度高分辨率月球地形图, 在空间覆盖、模型精度和空间分辨率上较早期模型均有较大改进. 利用该模型得到的月球平均半径为(1737013±2) m, 月球的赤道半径为(1737646±4) m, 月球的极半径为(1735843±4) m, 月球的形状扁率为1/963.7526, 月球的形状中心和质量中心在月固坐标系下的偏差为(-1.777, -0.730, 0.237) km. CLTM-s01所得到的月球形状基本参数与历史值相当, 但由于有更强的两极观测数据约束, 由该模型计算出的这些参数可信度更高.     

装配体结构有限元分析中的螺钉连接模型

在对螺钉连接进行理论分析计算的基础上,提出了在装配体结构线性动力学有限元分析中分别利用弹簧元和梁元模拟螺钉连接的两种方法,然后分别利用这两种方法在MSC.Patran/Nastran有限元分析软件平台下建立某卫星有效载荷部分结构组件的装配体动力学分析模型.通过对模型的模态分析结果与振动试验测试数据的比较,验证了这两种方法的正确性和有效性.     

多普勒测风激光雷达中马赫-曾德尔干涉仪的视场展宽技术研究

火星大气风速廓线探测对研究火星大气环境具有重要意义,基于马赫-曾德尔干涉仪的多普勒测风激光雷达相对于一般的相干/非相干多普勒测风激光雷达更适合于火星地基探测。为使马赫-曾德尔干涉仪对激光雷达中望远镜接收到的大视场角回波光信号进行频移检测,需要对马赫-曾德尔干涉仪进行视场展宽。对马赫-曾德尔干涉仪中棱镜式视场展宽技术与"猫眼"光学系统的视场展宽技术进行研究后发现,棱镜式视场展宽技术更具优势。设计并搭建了一套光程差为219 mm的马赫-曾德尔干涉仪,使用压电晶体扫描反射镜片的方式测量其对以11 mrad视场角入射的准平行光束的透射谱,得到干涉仪最大的干涉对比度为0.87,满足多普勒测风激光雷达的使用需求。结合地球大气环境分析了干涉仪干涉对比度随高度的变化,结果表明:虽然大光程差马赫-曾德尔干涉仪的干涉对比度在5 km以下低空大气中随高度增加有小幅下降,但仍可使用这种干涉仪进行大气风速探测。     

Laser-induced breakdown spectroscopy based detection of lunar soil simulants for moon exploration

A scientific goal of the moon exploration project is to perform elemental analysis on the moon surface. The assuming of using laser-induced breakdown spectroscopy (LIBS) for this goal has been put forward. The laser plasma used by LIBS is sensitive to the surrounding atmosphere and the moon has very low ambient gas pressure on the surface, so the study of the LIBS capabilities at the low pressure was carried out.     

An airborne pushbroom hyperspectral imager with wide field of view

An airborne pushbroom hyperspectral imager (APHI) with wide field (42?field of view) is presented. It is composed of two 22?field of view (FOV) imagers and can provide 1304 pixels in spatial dimension, 124 bands in spectral dimension in one frame. APHI has a bandwidth ranging from 400 to 900 nm. The spectral resolution is 5 nm and the spatial resolution is 0.6 m at 1000-m height. The implementation of this system is helpful to overcome the restriction of FOV in pushbroom hyperspectral imaging in a more feasible way. The electronic and optical designs are also introduced in detail.     

基于PXI平台的高速数据记录系统

以凌华科技的DAQStreaming系统为例,详细地论述了PXI平台在航空遥感数据记录系统中的应用前景.通过对系统体系结构的深入分析,指出了限制系统记录速度提高的瓶颈所在,结合最新发展的PCI Express总线技术和SATA硬盘存储技术,提出了一套基于PXIe平台和SATA磁盘阵列的高速数据记录方案,实现了记录速度的成倍提高.     

嫦娥一号CLTM-s01模型揭示和证认的月球地形新特征

月球的表面地形、物质成分和月壳厚度在月球正面和背面的分布均具有明显的二分性, 绕月卫星的重力和地形等探测数据实现了人类对月球表面这种差异性的研究. 利用嫦娥一号激光高度计探测数据获得的高精度月球地形模型CLTM-s01, 结合月球全球重力场分布情况, 提议出月球表面4个新的地形特征, 分别是位于背面的类撞击盆地Sternfeld- Lewis, 撞击盆地Fitzgerald-Jackson, 撞击坑Wugang和正面的火山沉积高地Yutu, 同时对以往被提议的一些大尺度撞击盆地的地形特征进行了分析和证认, 并根据盆地特征划分了不同的盆地等级.     

光子计数激光测距技术研究

光子计数激光雷达采用了灵敏度极高的单光子探测器,能够将激光雷达系统的灵敏度提高2—3个数量级,具有极大的发展潜力和技术优势。介绍和分析了光子计数激光测距技术的基本原理和优点。设计了光子计数激光雷达实验系统,采用盖革模式的雪崩二极管(Geiger-mode APD),开展了测距验证实验。实验结果表明,采用光子计数激光测距能够在单光子灵敏度和强噪声背景条件下,获取目标的距离信息,距离测量精度达到6.23 cm。     

啁啾调幅激光雷达对距离和速度的零差探测

构建了一种用线性调频信号去调制激光振幅的激光相干雷达实验系统.系统使用窄线宽激光器、马赫-曾德尔(M-Z)幅度调制器以及光纤零差光路,利用直接数字合成(DDS)技术所生成的啁啾信号对激光振幅进行调制,完成了对目标靶运动速度与距离的同时测量,对速度距离分辨率和误差进行了测试和分析,对信噪比(SNR)与系统探测能力的关系进...     

Optimization of the idler wavelength tunable cascaded optical parametric oscillator based on chirp-assisted aperiodically poled lithium niobate crystal

We present the numerical results for the optimization of the pump-to-idler conversion efficiencies of nanosecond idler wavelength tunable cascaded optical parametric oscillators(OPO) in different wavelength tuning ranges, where the primary signals from the OPO process are recycled to enhance the pump-to-idler conversion efficiencies via the simultaneous difference frequency generation(DFG) process by monolithic aperiodically poled, magnesium oxide doped lithium niobate(APMg LN) crystals. The APMg LN crystals are designed with different chirp parameters for the DFG process to broaden their thermal acceptance bandwidths to different extents. The idler wavelength tuning of the cascaded OPO is realized by changing the temperature of the designed APMg LN crystal and the cascaded oscillation is achieved in a single pump pass singly resonant linear cavity. The pump-to-idler conversion efficiencies with respect to the pump pulse duration and ratio of OPO coefficient to DFG coefficient are calculated by numerically solving the coupled wave equations. The optimal working conditions of the tunable cascaded OPOs pumped by pulses with energies of 350 μJ and 700 μJ are compared to obtain the general rules of optimization. It is concluded that the optimization becomes the interplay between the ratio of OPO coefficient to DFG coefficient and the pump pulse duration when the idler wavelength tuning range and the pump pulse energy are fixed. Besides, higher pump pulse energy is beneficial for reaching higher optimal pump-to-idler conversion efficiency as long as the APMg LN crystal is optimized according to this pump condition. To the best of our knowledge,this is the first numerical analysis of idler wavelength tunable cascaded OPOs based on chirp-assisted APMg LN crystals.