多通道高计数率单光子计数系统的设计与实现

光子计数探测具有极高的探测灵敏度，已成为大气探测激光雷达的主流探测手段。设计了一种基于FPGA的8通道高计数率单光子计数系统，提出了一种基于多相时钟过采样的光子脉冲检测方法，实现了2 ns的光子脉宽分辨率、200 MCPS的光子计数率、无死时间的连续多通道同步计数，具有高计数率、高实时性、高集成度的特点。系统已装备于北京遥测技术研究所研制的多波长拉曼偏振大气探测激光雷达中，在激光雷达大气遥感中发挥了重要作用。     

武汉上空对流层与平流层大气密度和温度探测的初步结果

利用武汉大学Rayleieh/钠荧光散射激光雷达和无线电探空仪进行联合探测的数据,反演出武汉地区上空(30.5°N,114.4°W)0—65km处的密度和温度分布曲线,并简单阐述了激光雷达的工作原理。将测量结果和MSISE-90参考大气模式比较,二者结果基本符合,温度廓线在中层顶附近和模式的差别约为3K。同时利用激光雷达探测到了中层大气中的重力波活动。     

Sodium lidar measurements of mesopause region temperatures at 23° S

A sodium lidar, capable of measuring temperature in the 80–100 km region, has been in operation at São José dos Campos (23° S, 46 W) since March 2007. Good quality data have been obtained for late autumn, winter and spring, but weather conditions make it extremely difficult to make measurements from mid-November to mid- February. We find the temperature structure to be strongly modulated by tides and gravity waves, but average profiles typically show a primary mesopause height close to 100 km with temperatures around 180 K, and a tendency for a secondary minimum of about 185 K to occur close to 90 km. Vertical temperature gradients greater than 50 K/km are sometimes seen even on profiles averaged over several hours. The strongest gradients are always positive and are frequently associated with strong gradients in sodium concentration. On the other hand, we frequently see rapid changes in the temperature profile, suggesting that models and non-local temperature measurements, as made by satellite radiometers, for example, are of little use in applications such as the analysis of gravity wave propagation seen in airglow images.     

青岛上空中层大气密度和温度的激光雷达探测

介绍了中国电波传播研究所瑞利散射激光雷达系统的结构和性能, 阐述了激光雷达探测中层大气密度和温度的工作原理, 给出了青岛地区中层大气密度和温度的初步探测结果. 通过与卫星、探空气球和大气模式数据的结果对比, 验证了激光雷达探测大气温度的可靠性. 基于2008-2009两年的观测, 获得了青岛地区上空中层大气温度的季节变化和平均分布. 激光雷达观测结果表明, 青岛地区平流层温度比CIRA86模式结果高, 且二者偏差呈夏秋季小、冬春季大的特点, 中间层温度则正好相反.      

北京地区重力波活动及其波谱的季节分布特性研究

利用激光雷达对北京地区上空Na层进行持续观测,通过连续三年累积的夜间观测数据对北京地区重力波活动及其波谱进行研究.根据重力波的线性理论计算,得到北京地区上空的大气密度扰动规律、空间功率谱和时间频率谱.通过选择重力波波长在1~8 km,具有特定波长以及特定周期为60,45,25 min的重力波活动辅助研究重力波的季节变化规律,结果表明北京地区重力波大气密度扰动具有夏季大、冬季小的活动规律.结合波源与背景风场的季节性变化规律,分析得出北京上空重力波活动季节性变化的主要原因为青藏高原地形和对流因素与我国北方地区季节性背景风场共同作用的结果.     

基于点云聚类评估的激光雷达鲁棒定位方法CSCD

基于先验地图的激光雷达定位方法在封闭工业场景下得到了广泛应用,然而环境变化、行人和车辆等动态物体的干扰会影响激光雷达与先验地图的匹配精度。提出了一种动态环境下基于点云聚类评估的三维激光雷达鲁棒定位方法:通过设定角度和距离双阈值,对点云深度图像进行分割聚类,相较于传统分割方法,分割结果对点云噪声更为鲁棒;通过对原始点云进行分割聚类,在粗匹配结果下评估聚类的匹配度,剔除误匹配聚类进行二次匹配以提高匹配精度;通过聚类评估的结果判断匹配成功和失败的点对,进而对点云整体匹配结果的正确性进行评估,相较于传统仅基于距离阈值的判断准则,具有更高的准确性;最终,分别通过公开数据集和实际试验验证了该算法的有效性。试验结果表明,相较于传统匹配方法,该方法有效提高了动态场景下的定位精度和匹配结果评估的准确度,定位误差可以维持在10cm以内。     

激光雷达系统仿真软件

从激光雷达约束条件入手 ,研究了通用激光雷达仿真模型 (GL M) ,其中包括大气传输模型、探测器噪声模型、发射与接收模型、目标反射数据库。着重分析、讨论了各种天气和系统条件下 ,对激光雷达性能的影响。根据模型 ,研制了通用仿真软件 ,最后给出了计算机仿真结果。     

无线电掩星和激光雷达观测结果比较

简要阐述了激光雷达和ＧＰＳ掩星探测大气的基本原理，并利用１９９６年１０月１４日１６２５ ＵＴ时 Ｂ本 ＴＭＵ钠和瑞利散射激光雷Ｂ（３９．２３°Ｅ、 ３５．３７°Ｎ）资＃，反演得到 ３０－５５ ｋｍ高度范围内大气密度和温度的观测结果，与此同时通过激光雷达上空的 ＧＰＳ掩星观测到的掩星切点处的观测结果进行了比较．结果表明：两种方法获得测出的密度廓线符合得很好；温度廓线的变化趋势也基本一致，但在某些高度上有较大的偏离．文中最后对比较结果作了简要分析，讨论了重力波对大气密度和温度廓线的影响．     

空间失稳目标线阵雷达成像机理及三维重建

利用线阵激光雷达载荷小、抗干扰能力强等优势，研究空间失稳目标动态测量技术。探究线阵激光雷达成像机理，建立空间失稳目标运动模型，提出基于双切片法的目标可测区域提取机制，实现线阵激光雷达对空间失稳目标的驻留观测扫描；以ICP(Iterative closest point)配准结果为先验信息，提出逆序重建方案，建立重建点云精度以及平均密度评价机制，分析数据冗余对重建精度的影响，采用采样降维的方法进行配准重建计算，提高重建结果精度；最后进行仿真实验检验分析，实验结果表明空间目标可测部位数据提取合理准确，数据输出频率可达 1 Hz ，重建结果满足任务指标要求，重建点云平均密度达到19 mm，重建点云精度达到90 mm，为地面验证及在轨应用提供数据支撑和参考。     

Single photon laser altimeter simulator and statistical signal processing

Spaceborne altimeters are common instruments onboard the deep space rendezvous spacecrafts. They provide range and topographic measurements critical in spacecraft navigation. Simultaneously, the receiver part may be utilized for Earth-to-satellite link, one way time transfer, and precise optical radiometry. The main advantage of single photon counting approach is the ability of processing signals with very low signal-to-noise ratio eliminating the need of large telescopes and high power laser source. Extremely small, rugged and compact microchip lasers can be employed. The major limiting factor, on the other hand, is the acquisition time needed to gather sufficient volume of data in repetitive measurements in order to process and evaluate the data appropriately. Statistical signal processing is adopted to detect signals with average strength much lower than one photon per measurement. A comprehensive simulator design and range signal processing algorithm are presented to identify a mission specific altimeter configuration. Typical mission scenarios (celestial body surface landing and topographical mapping) are simulated and evaluated. The high interest and promising single photon altimeter applications are low-orbit (∼10 km) and low-radial velocity (several m/s) topographical mapping (asteroids, Phobos and Deimos) and landing altimetry (∼10 km) where range evaluation repetition rates of ∼100 Hz and 0.1 m precision may be achieved. Moon landing and asteroid Itokawa topographical mapping scenario simulations are discussed in more detail.