CAS-1 lunar soil simulant

Lunar soil simulant is a geochemical reproduction of lunar regolith, and is needed for lunar science and engineering researches. This paper describes a new lunar soil simulant, CAS-1, prepared by the Chinese Academy of Sciences, to support lunar orbiter, soft-landing mission and sample return missions of China’s Lunar Exploration Program, which is scheduled for 2004–2020. Such simulants should match the samples returned from the Moon, all collected from the lunar regolith rather than outcrops. The average mineral and chemical composition of lunar soil sample returned from the Apollo 14 mission, which landed on the Fra Mauro Formation, is chosen as the model for the CAS-1 simulant. Source material for this simulant was a low-Ti basaltic scoria dated at 1600 years from the late Quaternary volcanic area in the Changbai Mountains of northeast China. The main minerals of this rock are pyroxene, olivine, and minor plagioclase, and about 20–40% modal glass. The scoria was analyzed by XRF and found to be chemically similar to Apollo 14 lunar sample 14163. It was crushed in an impact mill with a resulting median particle size 85.9 μm, similar to Apollo soils. Bulk density, shear resistance, complex permittivity, and reflectance spectra were also similar to Apollo 14 soil. We conclude that CAS-1 is an ideal lunar soil simulant for science and engineering research of future lunar exploration program.     

Lunar gravity field modeling critical analysis and challenges

This paper summarizes and provides a critical analysis of the historical developments of lunar gravitational models from the earliest use of ground based tracking systems of the Lunar Orbiter to the Lunar Prospector mission. This encompasses a comprehensive and critical analysis of the various methods used in the estimation of the gravity coefficients and the processing of large batches of diverse measurements and data types. It has been shown that weakness exists in the current models of the lunar gravity field, which is primarily due to the lack of far side lunar tracking data information, which makes the lunar potential modeling difficult but expected to be overcome as data from SELENE satellite-to-satellite tracking becomes available. Comparisons of various lunar models reveal an agreement in the low order coefficients of the spherical harmonics. However, substantial differences in the models exist in the higher-order harmonics. A numerical comparison has been presented showing the performance of all the contemporary lunar gravitational models used within the astrodynamics community and available in public domain. Improvements to the current models are part of a continuing process and the recent model improvements and future possibilities in lunar gravity modeling are discussed. A brief review of the recent missions has been presented. It is hoped that this critical review will benefit the researchers by presenting the historical as well as state of the art in this field.     

Theoretical modelling of X-ray fluorescence signals for different lunar compositions and dependence on solar activity

We present a forward modelling technique for calculating the surface X-ray spectra for a variety of lunar terrains. Our calculations considered variations in solar fluxes from solar quiescent condition to large flare activity (M1 flare), and expected elemental concentrations in the target, as well as yield, instrumental, and viewing geometry parameters for X-ray induced fluorescence from the lunar surface. Additionally, we present estimates of anticipated XRF signals from prominent K_α lines observable by a collimated 14 cm² X-ray detector from a 100 km lunar orbit with ∼20 km spatial resolution. Our results show that Mg, Al and Si characteristic K_α lines can be observed for all solar conditions. The Ca K_α lines line can be differentiated from a fixed background during more energetic solar conditions such as C1 and M1 flares, whereas Ti and Fe lines are identifiable only during C1 and M1 solar flare conditions for Apollo 12 site composition. Both the K_α X-ray intensity ratios of Mg/Si and Al/Si correlate well with concentration ratios of Mg/Si and Al/Si, respectively, for B1 and M1 solar conditions. The K_α X-ray intensity ratios of Fe/Si and Ca/Si correlates with concentration ratios of Fe/Si and Ca/Si, respectively, for M1 solar condition. In principle, the modelling technique outlined here can be used to determine absolute elemental abundances (Mg, Al, Si, Ca, Ti and Fe) from X-ray spectra measured during recent and future lunar missions.     

新型月球车的控制及实验研究

由于月球复杂的地形环境, 月球车作为复杂多体系统, 其动力学行为和驱动控制具有很多特性, 对其的分析也较简单系统复杂得多. 本文给出了对月球车控制的动力学、运动约束和运动学设计的数学模型, 并以跨越沟壑为例, 说明了协调控制过程. 同时设计和研制了基于气浮的独轮实验装置, 用于模拟月球的重力环境, 并研究协调了控制中各个车轮运动学和动力学参数的合理范围.      

月球探测器软着陆机构展开动力学仿真分析

可展开的软着陆机构是月球探测器的重要组成部分。以带间隙的多体系统动力学理论 为基础,针对一型采用四支撑悬臂式软着陆机构的月球探测器在ADAMS中建立了虚拟样机模 型,分别就主着陆腿系统结构柔性,主着陆腿与基体连接间隙,展开驱动力及探测器自旋等 因素对软着陆机构展开过程的影响进行了仿真分析。结果表明,在机构展开锁定瞬间由于结 构柔性会产生难以衰减的振动,而间隙在一定程度上有利于该振动衰减。展开驱动力越大, 展开越快,锁定激振振幅越大,但由展开进入稳定状态所需总时间可更短。探测器自旋则有 助于机构的展开,但自旋速度较高时对结构振动有明显影响。该结果可为软着陆机构展开方 案的设计提供帮助。
     

月球探测器TDI-CCD相机成像质量影响因素分析

TDI-CCD相机可以通过多级CCD积分,获得相对较高的信噪比,从1992年开始逐步广泛应用于航空和航天领域中的高分辨率成像任务中。目前TDI-CCD相机已成为高分辨率成像探测的重要手段。根据月球环绕探测任务中TDI-CCD相机的工作环境特点,定量分析了相机的姿态误差、速高比失配等因素对成像质量的影响,并对其中的主要影响因素——速高比失配,提出了适合于月球环绕探测任务特点的补偿途径。     

环月探测器自主天文导航系统的可观度分析

文章提出了在环月段以月球—探测器—恒星、月球—探测器—太阳这两个位置面和月心距等观测信息进行滤波的导航方法。通过对几种非线性系统可观性分析方法的比较,在基于误差协方差阵的可观性分析方法基础上,提出了以谱半径定义的可观度分析方法,并证明了定义的可观度指标与系统导航精度的关系,说明其能够定量描述系统可观的程度。最后仿真验证了这种可观度分析方法的可行性。     

月球探测器软着陆机构发展综述

综述了月球探测器软着陆机构的发展概况;分析了国际上月球探测器软着陆机构的结构组成、工作原理及特点。对不同展开机构和缓冲器特点进行了分析,预测了月球探测器软着陆机构的发展趋势。     

环月卫星成像敏感器对月姿态确定算法

紫外月球敏感器是大视场成像式敏感器,针对姿态确定算法,以MOSAIC可见光成像敏感器为例分析了传统圆拟合模式的适用性与不足;推证出在低轨道情况下曲线拟合出的月像几何中心与真实月心(nadir)不能等同;依据成像几何分析通过泰勒展开公式推导并提出了新的姿态角运算方法,保证了低轨道姿态运算精度;仿真结果显示新算法的姿态运算是非常有效的。     

基于嫦娥一号高能粒子数据的地球磁层屏蔽效应研究

月球绕地球运行轨道约有1/4位于地球磁层内,因此,地球磁层是否会为月球轨道附近高能粒子提供足够的磁场屏蔽对于探索月球活动具有重要影响.嫦娥一号是中国首颗绕月人造卫星,其绕月飞行的工作轨道距离月球表面200 km.通过对嫦娥一号高能粒子探测器(HPD)的探测数据进行分析,比较了当月球位于地球磁层内外6个不同能道(能量范围4～400 MeV)时质子通量的变化,发现当月球位于地球磁层内时,这些能道的质子通量并没有发生显著减少,结果表明地球磁层不能为月球轨道附近高能粒子提供显著的磁屏蔽.