地形信息熵/INS组合导航技术研究

应用信息熵的原理,利用不受外界干扰的地形信息作为导航系统的辅助信息,设计了一种地形信息熵最小方差匹配算法,它采用KALMAN滤波来实时修正惯性导航系统的误差。仿真试验结果表明,基于地形信息熵的辅助导航是一种自主式辅助导航模式,具有定位精度高的优点,可有效抑制惯导系统的误差,具有实际应用前景。     

The motion of a car moving on a terrain: A kinematic model

This work deals with the kinematic model of the motion of a car moving on a general rigid terrain. It is assumed that at each instant, each of the car's four wheels is in contact with the ground. Based on this assumption, a kinematic model for the motion of the car is derived.     

An equivalent soil mechanics formulation for rigid wheels in deformable terrain, with application to planetary exploration rovers

A simplified, closed-form version of the basic mechanics of a driven rigid wheel on low-cohesion deformable terrain is presented. This approach allows the formulation of an on-line terrain parameter estimation algorithm, which has important applications for planetary exploration rovers. Analytical comparisons of the original and simplified equations are presented, and are shown to closely agree. Experimental results from a single-wheel testbed operating in dry sand shows that the simplified equations can be used for mobility prediction with good accuracy. Methods for incorporating the simplified equations into an on-line terrain parameter algorithm are discussed.     

Stochastic simulation of infrared non-Gaussian natural terrain imagery

We describe a new technique for the fast simulation of natural IR imagery with non-Gaussian statistics. We pass samples of the imagery through an invertible pointwise nonlinear transform, to give samples of a new random field with Gaussian marginal probability density. We compute the correlation function for the transformed samples, and simulate Gaussian random fields (GRFs) with these correlations. Passing the simulated GRFs through the inverse transform gives our simulations of the original imagery. We discuss the effectiveness of this approach for simulating natural terrain backgrounds.     

Lower-hybrid turbulence in the near-surface lunar dusty plasmas

The results are presented of the first investigation of linear and nonlinear processes associated with waves which are related to the presence of magnetic fields in dusty plasmas at the Moon. Excitation of lower-hybrid turbulence in dusty plasmas near the lunar surface is studied. It is shown that the lower-hybrid turbulence can be generated wherever the Earth's magnetotail interacts with the near-surface dusty plasmas at the Moon. The electric fields appearing as a consequence of the presence of lower-hybrid turbulence are estimated. They can make a significant contribution to the total electric field above the lunar surface which should be taken into account in the future experimental investigation of electric fields at the Moon.     

Penumbra lunar eclipse observations reveal anomalous thermal performance of Lunakhod 2 reflectors

As the signal reflected by the corner-cube reflector arrays is very weak and easily submerged during the full moon, we analyze the influence of the thermal effect of corner-cube reflector arrays on the intensity of lunar laser ranging echo. Laser ranging measurements during the penumbra lunar eclipse verify suspected thermal deformation in the Lunakhod 2 reflectors. Signal levels vary over two orders of magnitude as the penumbra eclipse progresses. This can be explained by the change in the dihedral angle of the corner-cube reflectors caused by the temperature. The results show that when the dihedral angle errors reach 1', the energy is reduced by 100 times compared with the ideal corner-cube reflector. In the experiment, our findings suggest that when the corner-cube reflector arrays enter the penumbra of the earth, the effective echo signal level which reaches 0.18 photons/s far exceeds the historical level of the full moon. However, 11 minutes after the penumbra lunar eclipse, the effective echo rate of Lunakhod 2 will drop two orders of magnitude. The mechanism can explain the acute signal deficit observed at full moon.     

变分伴随正则化方法从雷达回波反演海洋波导 Ⅰ.理论推导部分

针对传统统计反演算法在雷达回波反演海洋波导(RFC)方面计算量过大的问题,提出一种变分伴随正则化物理反演算法.在变分伴随方法中分别导出切线性模式、伴随方程及伴随边界条件、伴随方程求解表达式、以及泛函梯度的数学表达形式;讨论了伴随方法求泛函梯度对复方程如何协调的问题.考虑到雷达电磁波传播的特征,选择了适当的正则化项来解决反演中的不适定问题.最后给出反演算法实施中的迭代格式.     

嫦娥一号卫星成像光谱仪光学系统设计与在轨评估

介绍了嫦娥一号卫星干涉成像光谱仪的科学目标、总体设计思想、方案选型、工作原理、光学实施方案、光学系统设计及评价、空间环境适应性考虑、发射前光学图像质量检测、在轨运行情况及在轨性能评测.     

数字地形技术在环境规划设计中的应用

近年来基于地理信息系统层面的数字地形技术的发展和完善,使得环境规划设计领域有可能利用其技术实现各种尺度的空间分析,从而改善原有操作环节,提高效率和精度,使准确的地形分析结论指导规划和设计.数字地形技术在环境规划设计中的应用存在衔接问题,首先体现在现状测绘图纸中的图元数据与建立数字地形所需的数据源存在着差异,应将其转换,必要时将通过对绘图平台的二次开发来完成数据源的兼容性处理.其次应当选择合适的地形模块来完成相关的数字分析.通过必要的技术衔接,在规划设计中,将实现对场地的基本地形分析、叠置分析、可视化以及其他方面的工程应用.该技术的应用是信息化规划设计的重要尝试,将在环境规划设计中预先体现出其优越性.     

基于贝叶斯方法的地形辅助导航算法

提出并建立了一种基于贝叶斯方法的地形辅助导航(TAN)模型,推导了模型公式。针对该模型,应用最大后验估计方法,给出了一种近似的实现方法,即基于贝叶斯方法的地形辅助导航算法。仿真结果表明,该算法的均方根误差和圆概率误差等性能均优于SITAN(桑地亚惯性地形辅助导航)算法。