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91.
为实现水平非均匀分布的低层大气气溶胶光学特性的遥感探测,提出一种基于双扫描激光雷达的气溶胶精细探测方法.该方法以扫描激光雷达为遥感探测工具,通过双激光雷达相向交叉扫描工作模式,实现对同一空域近地表气溶胶全视野剖面的交叉探测,从而提供双激光雷达方程组以精确求解气溶胶消光和后向散射系数.在数据反演过程中,通过对交叉扫描区域进行坐标化和网格化处理、网格像素单元的初值预设,以及双扫描激光雷达方程组的数值逼近反演得到气溶胶消光.利用长距离扫描激光雷达的数据对该方法进行验证,结果表明,该方法与多角度方法反演所得到的结果随高度变化的趋势具有高度的一致性;同时双扫描激光雷达可提供交叉扫描区域剖面的气溶胶浓度分布,相比于单条廓线具有较大的优势. 相似文献
92.
GJ 436b is a Neptune-size planet with 23.2 Earth masses in an elliptical orbit of period 2.64 days and eccentricity 0.16.
With a typical tidal dissipation factor (Q′∼106) as that of a giant planet with convective envelope, its orbital circularization timescale under internal tidal dissipation
is around 1 Ga, at least two times less than the stellar age (> 3 Ga). A plausible mechanism is that the eccentricity of GJ
436b is modulated by a planetary companion due to their mutual perturbation. Here we investigate this possibility from the
dynamical viewpoint. A general method is given to predict the possible locations of the dynamically coupled companions, including
nearby/distance non-resonant or mean motion resonance orbits with the first planet. Applying the method to GJ 436 system,
we find it is very unlikely that the eccentricity of GJ 436b is maintained at the present location by a nearby/distance companion
through secular perturbation or mean motion resonance. In fact, in all these simulated cases, GJ 436b will undergo eccentricity
damp and orbital decay, leaving the present location within the stellar age. However, these results do not rule out the possible
existence of planet companions in nearby/distance orbits, although they are not able to maintain the eccentricity of GJ 436b.
Supported by the National Natural Science Foundation of China (Grant Nos. 10833001 and 10778603) and the National Basic Research
Program of China (Grant No. 2007CB4800) 相似文献
93.
基于大气湍流效应的双波长激光传输特性实验研究 总被引:1,自引:0,他引:1
为研究大气湍流作用下不同波长激光信号的传输特性,建立了基于双波长条件下的激光光束传输实验测试系统,在此基础上进行了室外实验测量,得到了双波长光束同信道传输时的光束漂移和光强起伏变化的测试数据。实验结果表明,大气湍流对激光信号的传输具有较大的影响,且光强的闪烁系数与波长有很大的关系,选择波长较长的激光束可减少湍流对光强起伏的影响;光束质心漂移具有很大的随机性,且其质心变化与波长之间无明显的直接联系。实验测试数据结果与大气湍流理论相符合,对空间大气通信具有一定的参考价值。 相似文献
94.
95.
Propagation properties of a decentered general astigmatic partially coherent beam (i.e., decentered twisted anisotropic Gaussian Schell-model beam) in a turbulent atmosphere are investigated. Analytical formulas for the cross-spectral density and decentered parameter of a decentered astigmatic partially coherent beam propagating in a turbulent atmosphere are derived. Irradiance properties of a decentered astigmatic partially coherent beam in a turbulent atmosphere are studied graphically, and are found to be quite different from its properties in free space. 相似文献
96.
Dynamic wind loads, thermal expansion and other mechanical reasons cause optical platform mounts to sway. The sway distorts the alignment between transmitters and receivers, causing random pointing jitter, the outcome of which is the phase fluctuation of optical waves from the transmitter. Furthermore, atmospheric turbulence causes fluctuations in the phase of those optical waves. By using the extended Huygens-Fresnel principle, both phase fluctuations are considered and an analytic formulation for the angle-of-arrival variance of optical waves propagating through turbulent atmosphere in the presence of motion-induced pointing jitter is derived. The result shows that the angle-of-arrival variance of optical waves under the combined impact of motion-induced pointing jitter and atmospheric turbulence is the sum of the angle-of-arrival variances induced by them independently. 相似文献
97.
The scintillation properties of astigmatic annular beams in a weak turbulent atmosphere are investigated. Expression for the on-axis scintillation index of an astigmatic annular beam is derived. It is found that the scintillation index of an astigmatic annular beam can be smaller than that of a Gaussian beam, an elliptical Gaussian beam and a stigmatic annular beam in a weak turbulent atmosphere under certain conditions. The scintillation properties of astigmatic annular beams are closely controlled by its beam parameters. 相似文献
98.
99.
A. Doicu T. Trautmann 《Journal of Quantitative Spectroscopy & Radiative Transfer》2009,110(17):1851-1863
Several methods for solving the radiative transfer equation in a spherical atmosphere are presented. These methods include the long characteristic Picard iteration, and the conventional and the accelerated short characteristic Picard iteration. Approximate methods as for instance the Picard iteration methods with open boundaries are also discussed. The analysis is focussed on the computational efficiency and accuracy of the proposed method and their applicability to atmospheric remote sensing. 相似文献
100.