月球激光测距中的关键物理与技术问题

根据国际上公开发表利用的1969-1972年美国Apollo 11、14、15宇航员放置在月球上的三个角反射器以及1970-1971年苏联无人登月车放置的两个角反射器进行的月球激光测距的论文和技术文献,讨论了月球激光测距中的几个关键物理和技术问题,主要包括:1)角反射器阵列指向与其月面位置的精确定位;2)角反射器激光回...     

Error analysis on dihedral angle of corner-cube reflectors in Fourier transform spectrometer北大核心CSCD

Fourier transform spectrometer is an important spectral analysis instrument. To research the influence of the dihedral angle error of corner-cube reflectors on interference quality of oscillating Fourier transform spectrometer, the theoretical analysis and computer simulation were carried out. According to the oscillating Fourier transform spectrometer model, the mathematical expressions of the interference intensity and modulation depth with dihedral angle error were deduced. The tolerance of dihedral angle was determined by the modulation depth criterion. The optical design software Zemax was used to establish the model for simulation and verify the results of theoretical derivation. According to the modulation depth criterion, the tolerance of dihedral angle obtained by the theoretical model is 2.52″, and that obtained by the Zemax simulation is 2.38″. The error is 0.14″, which is acceptable. The analysis results show that the established theoretical model is reasonable, which has certain reference value for the design and installation of oscillating Fourier transform spectrometers. © 2022 Editorial office of Journal of Applied Optics. All rights reserved.     

月球表面热辐射计算模型研究

为深入了解月球表面的热环境,根据月表红外发射率随温度变化以及太阳光反射率随入射方向变化的特点,建立了月表的多温段变反射率辐射计算模型.将该模型与月壤非稳态导热微分方程结合,并考虑日、月相对运动关系,形成了月表温度计算方法.在计算程序验证的基础上,分析了月表温度的变化规律与控制因素,比较了月海与月陆两种月表单元的温度差异...     

基本参数法在地面验证实验中的的应用

As the nearest celestial body to the earth, the moon has become a hot spot again in astronomy field recently. The element analysis is a much important subject in many lunar projects. Remote X-ray spectrometry plays an important role in the geochemical exploration of the solar bodies. Because of the quasi-vacuum atmosphere on the moon, which has no absorption of X-ray, the X-ray fluorescence analysis is an effective way to determine the elemental abundance of lunar surface. The CE-1 X-ray fluorescence spectrometer （CE-1/XFS） aims to map the major elemental compositions on the lunar surface. This paper describes a method for quantitative analysis of elemental compositions. A series of ground base experiments are done to examine the capability of XFS. The obtained results, which show a reasonable agreement with the certified values at a 30% uncertainty level for major elements, are presented.     

Terrestrial Seismic Activity and Neutrons from the Surface of the Earth Associated with Lunar and Solar Tides

drastic increase in the flux of thermal neutrons of secondary cosmic radiation coming from the Earth was observed in the Pamir Mountains during the solar eclipse of July 22, 1990. In the following years, such phenomena were observed on each new moon and each full moon, when lunar and solar tides combine to produce an exceptionally high resultant tide. Tidal forces may serve as a trigger for the release of the deepearth seismic energy in a certain region. This directed our attention to the search for a temporal correlation between earthquakes and new and full moons, which may help identify a new type of seismic activity precursor. Such a correlation was found in the circum-Pacific belt and the adjacent regions at latitudes above 40° N and 10° S. The results of daytime measurements of the thermal neutron flux from the surface of the Earth in the Western Pamirs (Moskvin Glade, 4200 m above sea level) on August 1–14, 1994, are reported in the present study. Since these days were quiet in terms of weather and heliophysical and geophysical activity, the intensity of neutrons of secondary cosmic radiation was expected to remain almost constant. However, twofold (or even larger) intraday variations of the neutron count rate were observed on August 1–14, 1994. These quiet measurement conditions rule out the possibility that these bursts were associated with certain known extraterrestrial factors. It has been demonstrated that the observed neutron-intensity peaks were produced by lunar and solar tides. These results confirm that tidal forces play a prominent part in the generation of neutron fluxes from the surface of the Earth. The Astronomical Yearbook for 1994 published by the Russian Academy of Sciences was used in the present study.     

Distribution of charged lunar dust in the south polar region of the moon

Lunar dust is one of the most threatening problems confronting the return of human beings to the moon. In this work we studied the spatial distribution behavior of charged lunar dust in the solar wind plasma environment in the south polar region of the moon and considered the influence of a mini-crater using Spacecraft Plasma Interactions Software. The distribution of dust and plasma at low solar altitude angles of 20° and 0° was studied, and the spatial density of lunar dust was ~10^10.4 m^-3 and ~10^11.5 m^-3, respectively. This is because a higher surface potential will result in transportation of small dust particles and photoelectrons can also neutralize positively charged lunar dust. The dust density in the plasma void region created by a mini-crater with a 5 m high wall was studied. We obtained a quasi-neutral electric environment in the plasma void region of the mini-crater, and the dust density was about a magnitude lower than that in other regions. The dust risk to a spacesuit is much lower on the nightside than on the dayside, but there is severe charged lunar dust transport in the region between light and shade, which is dominated by the difference in surface and plasma potential caused by photoelectrons.     

基于月面图像的大气波前倾斜量提取算法的性能分析

 为了提高月球激光测距试验中的回波光子数,考虑将自适应光学技术应用于云南天文台1.2 m光学望远镜,以实时校正望远镜跟踪误差和由于大气湍流的影响而造成的到达月球表面的激光束的扩展与漂移效应。针对月面为低对比度扩展源的特点,利用互相关函数法及绝对差分算法对采集的月面图像进行了大气波前倾斜量的提取。模拟了未去除和去除大气波前倾斜量的月面长曝光图像,发现去除大气波前倾斜量后的图像对比度较未去除有了相应提高。研究表明：月球激光测距试验中,绝对差分算法更适合用来提取大气波前倾斜量。     

Quantitative analysis results of CE-1 X-ray fluorescence spectrometer ground base experiment

As the nearest celestial body to the earth, the moon has become a hot spot again in astronomy field recently. The element analysis is a much important subject in many lunar projects. Remote X-ray spectrometry plays an important role in the geochemical exploration of the solar bodies. Because of th equasi-vacuum atmosphere on the moon, which has no absorption of X-ray, the X-ray fluorescence analysis is an effective way to determine the elemental abundance of lunar surface. The CE-1 X-ray fluorescence spectrometer (CE-1/XFS) aims to map the major elemental compositions on the lunar surface. This paper describes a method for quantitative analysis of elemental compositions. A series of ground base experiments are done to examine the capability of XFS. The obtained results, which show a reasonable agreement with the certified values at a 30% uncertainty level for major elements, are presented.     

猫眼谐振腔氦氖激光器理论分析

猫眼逆向器作为谐振腔镜与一个凹面镜构成猫眼激光谐振腔.精确计算了三种猫眼逆向器(即理想猫眼逆向器和两种存在误差的猫眼逆向器)的逆向平行反射性，并对应用这三种猫眼逆向器的谐振腔中高斯光束的各项参数进行了深入分析，得出结论：对于高斯光束，凸透镜的焦距、凹面镜曲率半径、凸透镜与凹面镜间距三者相等的猫眼逆向器为理想逆向器，其逆向平行反射性最好，此时猫眼谐振腔处于理想状态，基模模体积最大，远场发散角最小，稳定性最好；在猫眼谐振腔的设计中，要尽量减小猫眼逆向器中凸透镜的焦距，增大凹面输出镜的曲率半径；猫眼逆向器存在误差时谐振腔的各项性能将受到影响.为猫眼谐振腔激光器的设计提供了理论依据.     

月表尘埃颗粒带电的机理及应用研究

研究月尘颗粒在电子束环境下以及紫外源辐照下的带电机理,利用数值方法模拟月尘颗粒在不同背景环境下的充电过程,以探索月表尘埃颗粒的带电机理,进而便于地面月尘环境模拟装置选择合适的月尘带电方式进行空间模拟实验.给出了尘埃在电子束环境下的充电方程,并将紫外辐射带电与具体应用相结合.通过模拟结果可知,在电子束环境下,月尘表面的电荷数随粒径尺寸增大,随电子枪辐照束斑半径减少,随电子枪流强的增加而增多;在紫外源的辐照下,月尘表面电荷数随颗粒尺寸的增大以及紫外线辐照度的增加而增多.由月尘颗粒受太阳紫外辐照带电的数值模拟结果可知,月尘需要在太阳长时间的辐照下才可以带上可观的电荷数,地面模拟该过程需增加辐照源来加速实验.通过模拟结果的分析比较并结合"空间环境模拟装置"中对月尘舱的设计要求,最终优选紫外源辐照带电方式作为月尘颗粒的带电方案.     

开放光路TDLAS气体检测系统光学接收组件设计

针对开放光路TDLAS(可调谐半导体激光吸收光谱技术)气体检测系统中,由于角反射器在生产及使用过程中表面光洁度下降及大气传输扰动造成回波信号入射方向与接收透镜光轴非严格平行,从而导致系统探测灵敏度下降的问题,分析回波信号与菲涅尔透镜光轴夹角不同时的汇聚点偏移量,设计了由圆锥体反射器和抛物面反射器组成的二次光学元件,并运用TracePro光学软件对其参数进行优化。在回波光线-6°~6°入射角偏差范围条件下对优化设计的光学接收组件进行聚光特性模拟。模拟结果表明:优化设计的光学接收组件接收角为4.9°,光学效率为78.24%,与单独菲涅尔透镜及菲涅尔透镜-复合抛物面聚光器(CPC)光学接收组件相比聚光性能明显提高,适用于实际检测过程。     

角锥棱镜腔主动调Q绿光固体激光器的研究

为了保证激光器在高重复频率运转时的输出能量不下降,采用角锥棱镜作为主动调Q激光器的全反射镜,利用其退偏特性和腔外双通倍频技术,在重复频率为25Hz时,532nm绿光的输出能量比1Hz时上升约6．9％,可满足水下激光主动成像系统对激光光源的要求。     

Application of a corner-cube reflector in nanosecond radar tomography

Experimental results are presented on the nanosecond radar application for test site tomography with radar calibration by a corner-cube reflector. It is demonstrated that the presence of the corner-cube reflector leads to the occurrence of false targets that can be used for detection of weakly reflecting targets. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 91–93, November, 2008.     

平面光学镜低温温度场和热变形分析方法

在综合分析了温度场和热变形理论分析方法的基础上,提出了对空间光学系统中平面光学反射镜进行有限元分析具体方法;介绍了温度场特性经典理论,并对径向温度分布遵循二次规律的表达式作了简单推导;同时介绍了温度变化引起光学表面的Zern ike多项式法和用热力矩分析平面圆形板面形的方法;最后给出了用ANSYS和I-DEAS软件对联合光学元件热变形的计算流程。     

Terahertz-wave parametric oscillator with a misalignment-resistant tuning cavity

We demonstrate a terahertz-wave parametric oscillator (TPO) with a corner-cube resonator consisting of a corner-cube prism (CCP) and a flat mirror. By using the cavity configuration proposed in this Letter, the generation of tunable monochromatic terahertz (THz) waves can be achieved just by rotating the flat mirror instead of rotating the TPO cavity relative to the pump beam. The THz-wave output intensity and pulse width can be controlled periodically by rotating the CCP around the cavity axis. The TPO stability against cavity misalignment is significantly improved by at least 1 to 2 orders of magnitude compared with the conventional plane-parallel resonator configuration.     

红外连续激光反射镜热畸变的有限元分析

 基于热传导方程和热弹方程，利用有限元分析方法，就光斑尺寸远大于或接近于基底材料热扩散长度的情况以及反射镜在固定或自由的边界条件下，分别计算了硅和石英两种基底材料多层膜红外连续激光反射镜的最大温升、最大形变及最大热应力，并探讨了它们随光斑尺寸的变化规律。结果表明：在自由边界条件下，反射镜表面的最大轴向位移与光斑半径之间近似为线性关系；而在固定边界条件下，反射镜的最大热应力与光斑半径之间近似为线性关系；反射镜的夹持状态对最大轴向位移及最大热应力的影响随着光斑尺寸的增加而增强；在相同的入射激光光源及相同的边界条件下，硅镜具有较低的温升值或较高的抗热损伤阈值，而石英镜具有较好的抗热畸变特性。     

三反射式柱面光学系统设计及优化

针对传统单片柱透镜和柱面反射镜成像光束不理想以及视场通常小于1°,提出并设计了一种三反射式柱面结构.对柱面光线追迹及单片柱面镜成像进行了深入分析,分别设计了三反射式圆柱面和二次曲线柱面系统,提出了一种基于抛物柱面镜理想线聚焦的新型像差优化方法,使其在子午面方向各视场调制传递函数得到最佳优化,并达到成像光谱仪等在狭缝方向卜高空间分辨率要求.其子午面总视场均达到了3°,在45 lp/mm分辨率条件下,边缘视场子午面方向的调制传递函数分别优于0.2和0.6.     

移相式干涉仪在锥体棱镜角度测试中的应用

为了实时、高精度地测试光学零件，对移相式数字波面干涉仪在锥体棱镜角度测试中的应用进行了研究。通过锥体棱镜二面角偏差计算方法得到了二面角偏差和干涉波面之间的关系，分析了干涉波面的形状与锥体棱镜综合误差的关系，编写了锥体棱镜角度和综合误差测试程序，并且在移相式数字波面干涉仪和ZYGO干涉仪上分别对锥体棱镜进行测试，给出了2者的比较测试结果。结果表明，移相式数字波面干涉仪测量锥体棱镜二面角偏差的误差在0.3″范围内，RMS值的测量误差在λ/50内；提出的方法可实现检测过程的自动化。     

光学反射镜柔性锥套连接结构的设计与分析

针对空间光学遥感器反射镜结构刚度高、热尺寸稳定性差的状况,设计了一种柔性锥套结构,它在保持结构刚度满足力学要求的同时,使反射镜具有良好的热尺寸稳定性。对某光学反射镜组件中的柔性锥套进行了合理的结构设计,并对柔性铰链参数进行了分析,采用有限元法对反射镜组件的非柔性锥套连接结构和柔性锥套连接结构在自重和热两种工况下的反射镜面形精度进行了仿真分析。分析结果表明:由柔性锥套连接的反射镜在自重工况下面形PV值较非柔性锥套连接形式变化不大,而热变形明显好于非锥套连接的面形精度,PV值由43.9nm降到了27.5nm,对热的贡献较大;连接在整机工况下的反射镜组件的反射镜面形精度可满足遥感器的成像质量要求,保证了结构的热尺寸稳定性。因此这种柔性锥套连接结构在实际遥感器结构中是合理可行的。     

A 'Hi-Fi' Cartesian feedback spectrometer for precise quantitation and superior performance

The use of Cartesian electronic feedback for effecting a major improvement in the functioning of magnetic resonance instrumentation is reported. The dependences of both flip angle and signal strength upon probe loading, matching, and tuning are virtually eliminated. Thus, for a chosen probe, sample geometry and flip angle, the free induction decay signal strength is rendered solely dependent upon the number of nuclei. The instrument therefore becomes capable of absolute calibration. In addition, phase and amplitude distortion of selective pulses, introduced by crossed diodes, power amplifier heating, etc., is virtually eliminated, as are radiation damping and phase modulation caused by probe vibration. The use of multiple probes at the same frequency, for example quadrature probes and phased arrays, is also simplified as the effects of interactions between such probes are typically reduced by two orders of magnitude.