火星空间环境磁场探测研究——"萤火1号"磁强计的研制与应用

文章介绍了"萤火1号"卫星对火星空问环境磁场进行探测的目的、意义及采用的方式方法.研究火星的空间环境离不开火星磁场,它对于火星弓激波、磁鞘、电离层、大气等绝大多数空间环境效应都有着深刻的影响,因此"萤火1号"卫星安装了一台重要的科学探测载荷--高精度磁强计,以满足科学研究和应用目标的需求.磁强计从原理选择到具体没计,都考虑到了火星轨道严酷的工作环境和科学目标所需的测量要求.通过"萤火1号"装星前的地面标定测试实验,验证了高精度磁强计可以在-140-75℃温度范围内测量±256nT以内的磁场,分辨率达到了0.01nT,带宽内总噪声小于0.03nT,能够胜任"萤火1号"对火星空间环境探测的科学任务."萤火1号"火星探测器将于2011年与俄罗斯的"福布斯-土壤"一同飞往火星,这是人类送往火星最精密的磁场探测器之一,将对火星空间环境磁场结构和动力学过程进行精密而详细的探测.     

火星重力场研究现状及发展趋势

针对近年来月球与火星探测成为各航天大国的热点,以及中国首个火星探测计划"萤火1号"拟定的科学研究目标,文章对火星重力场模犁的历史、现状及展望做了简要描述.文中首先探讨了火星探测的多重意义和火星重力场在火星探测中起到的重要作用;接着介绍了火星重力场模型发展的历史和现状;最后介绍了利用中国"萤火1号"轨道跟踪数据对火星重力场模型的可能贡献,在此基础上对中国未来火星重力场探测提出了设想.     

用于火星电离层探测的星-星无线电掩星技术

火星和地球类似,周围束缚了不同密度的电离层.利用无线电掩星技术可以对火星电离层进行观测.星-地无线电掩星在探测精度和探测区域方面都受到一定的限制.中俄联合火星探测计划将于2011年10月一箭双星发射俄罗斯的Phobos-Grunt探测器和中国的萤火1号火星探测器.该计划将开展国际上首次火星电离层的星-星无线电掩星观测试验,重点是对星-地无线电掩星无法观测的正午和子夜区域的火星电离层进行探测.星-星无线电掩星观测试验采用双频工作模式,接收机灵敏度为-145dBm,相位测量精度优于5%周.在地面对接收机进行了动态模拟测试,测试得到的相位数据能很好地反演出火星电离层电子密度廓线.     

星-地无线电掩星技术探测火星大气和电离层

历史上几乎所有的行星探测任务都开展了无线电掩星实验,以探测行星的大气、电离层、行星环以及磁场,并取得了很多重要的科学成果.掩星发生时刻前后,测量航天器发出的信号穿过行星电离层和大气层时被遮掩而引起的信号频率、相位、幅度或极化等物理特性的变化,通过某种反演技术,可以得到大气的折射率廓线,推出中性大气的密度、温度、压强廓线以及电离层的电子浓度廓线.文章嗣绕中国"萤火1号"火星探测器(YH-1)火星探测计划中将要开展的星-地无线电掩星实验,介绍了该技术用于探测火星大气和电离层的相关情况.     

超高精度的甚长基线干涉相位时延推导法及其在我国的应用前景

文章简要介绍了同波束甚长基线干涉(VLBI)观测法和相位时延推导法,报道了上海-乌鲁木齐基线的误差为0.0005m的差分相位时延的观测结果,介绍了"萤火1号"和"福布斯"探测器的同波束VLBI观测技术及正在研究的相位时延推定新方法,展望了超高精度的VLBI相位时延在中国深空探测中的应用前景.     

"火星快车"下视雷达对火星电离层探测简介

火星是近年来深空探测的热点,对火星电离层的观测和研究是火星探测的主要内容之一.欧洲航天局2003年发射了火星探测器"火星快车",它所搭载的下视雷达MARSIS(火星地表和电离层探测雷达)为火星电离层探测提供了大量数据,文章简单介绍了利用MARSIS探测火星电离层的基本原理,探测数据的结构和利用这些探测数据进行电离层研究的现状.     

开环多普勒技术用于火星快车的观测验证

利用中国甚长基线干涉(very long baseline interferometry,缩写为VLBI)网天线资源以及"嫦娥一号"(Chang'e-1,缩写为CE-1)32星观测试验,首次实现了中国深空任务的开环多普勒测量.这一新的测量技术应用于欧洲航天局(European Space Agency,缩写为ESA)的"火星快车"(Mars Express,缩写为MEX)探测器的观测实验中.实验结果显示,在1s积分情况下,开环多普勒(三程)测量精度随机误差达到1mm/s,这一精度与通常的闭环多普勒(双程)水平相当.开环多普勒(三程)数据已经开始尝试用于卫星的定轨,今后有关开环多普勒数据的科学应用也在准备中.     

时分复用激光干涉测速技术研究

为了探索和发展瞬态激光干涉测量技术,本文从理论上对激光差频干涉测速度技术进行了分析,并对该技术的应用基础和发展前景进行了剖析.基于对该技术中关键技术的分析、讨论,提出了时分复用激光干涉测速技术的概念.充分利用了激光差频干涉测速技术中的延迟时间τ,在时间段0~τ和τ之后,激光干涉分别体现的是测位移技术和测速度技术,从而可较好地确定冲击与爆轰等物理过程中的第一冲击前沿的速度值(解决条纹丢失的不确定性);同时在硬件要求不太高(降低对记录用示波器等的带宽和采样率的要求)的情况下,保证有较高的速度测量上限.结合爆轰与冲击物理过程特性的考虑,通过选择合适的干涉测试技术参量,设计并建立了光纤时分复用激光干涉测速系统,进行了时分复用激光干涉测速技术的初步应用研究,获得了较好的应用结果,从而验证了该技术的有效性.     

空间引力波探测望远镜初步设计与分析

引力波的直接观测已开启引力波天文学的新篇章,爱因斯坦的百年预言终获证实。空间引力波探测器使得探测0.1 m Hz~1 Hz频段丰富的引力波源成为可能,与地面引力波探测器互为补充,才可实现更加宽广波段的引力波探测,揭开宇宙早期的更多秘密。空间激光干涉引力波探测采用外差干涉测量技术,测量间距百万公里的两自由悬浮测试质量间10 pm量级的变化量。望远镜是激光干涉测量系统的重要组成部分,1 pm的光程稳定性及苛刻的杂散光要求,不同于传统的几何成像望远镜。本文根据空间太极计划任务需求,对望远镜的功能及技术要求进行了分析,并完成了原理样机的初步方案设计,针对百万公里远场波前分布,分析了望远镜系统的敏感性,同时完成了在轨光机热集成仿真,为后面原理样机的研制奠定了技术基础。     

激光干涉引力波探测器——人类的宇宙助听器

爱因斯坦预言引力波100周年之际,人类首次直接探测到引力波信号。文章简单介绍了这次的主角——高新激光干涉引力波天文台(advanced LIGO)的光学与激光部分技术。激光干涉引力波探测器,本质上是一个迈克尔孙干涉仪。原初的迈克尔孙干涉仪也曾在否定以太理论、促使相对论创立的过程中起关键作用。而基于爱因斯坦受激发射理论发展起来的激光技术也在引力波探测中立下汗马功劳。出于协同测量与定位以及扩展引力波探测频段等方面的考虑,除LIGO之外,还有多个地面和空间激光干涉引力波探测器在建或在研。可以预计,当前只是引力波探测技术与引力波天文学发展的开端。     

Mössbauer spectroscopy in space

Nearly 40 years after the discovery of the Mössbauer effect for the first time a Mössbauer spectrometer will leave our planet to explore in situ the surface of another solar system body: the red planet Mars [1]. We are currently developing a miniaturized Mössbauer spectrometer (MIMOS) which is part of the scientific payload of the Russian Mars96 mission, to be launched within the next 2–4 years [2,3]. To fulfill the requirements for a space mission to the planet Mars, all parts of the spectrometer had to be extremely miniaturized and ruggedized to withstand the space flight and Mars environmental conditions. The relevant parts (e.g. drive, detector system, electronics etc.) will be described in more detail and its characteristics compared to standard systems. Because of this new development there now is a growing interest to include a Mössbauer (MB) instrument in future space missions to other solar system bodies as for instance Venus, the terrestrial Moon, and a comet nucleus. Because of extremely different environmental conditions (e.g. nearly zero gravity on the surface of a comet nucleus, high pressure and temperature on the surface of Venus, etc.) different instrument designs and concepts are required for different missions. We will present some ideas for various types of missions, as well as the motivation for using Mössbauer spectroscopy in these cases.     

Very Long Baseline Interferometry — a high precision tool for geodesy and astrometry

Very Long Baseline Interferometry is able to provide a direct geometrical tie to the extragalactic radio sources which represent the best possible realization of an inertial system. By this token, VLBI can measure Earth rotation and orientation as well as precise station positions and their velocities without involving the gravity field of the Earth. In the broader context of Earth observation and the monitoring of geodynamic processes, this one and many more unique features have allowed the VLBI technique to achieve pioneering feats such as the determination of present-day plate tectonic motions, post glacial rebound, sub-daily Earth rotation variations and parameters of general relativity. In this contribution, a brief outline of the VLBI technique and the models used in geodetic data analysis will be given before some of the most important achievements to date will be passed in review and future developments will be indicated.     

Statistical theory of asteroid escape rates

Transition states in phase space are identified and shown to regulate the rate of escape of asteroids temporarily captured in circumplanetary orbits. The transition states, similar to those occurring in chemical reaction dynamics, are then used to develop a statistical semianalytical theory for the rate of escape of asteroids temporarily captured by Mars. Theory and numerical simulations are found to agree to better than 1%. These calculations suggest that further development of transition state theory in celestial mechanics, as an alternative to large-scale numerical simulations, will be a fruitful approach to mass transport calculations.     

Mössbauer spectroscopy and the iron on Mars

Both the USSR and US have plans of performing rover missions and sample return missions to the planet Mars in the coming decade. There may be possibilities of performingin situ Mössbauer spectroscopy on Mars or on fresh samples returned to a space station.     

Infrared remote sensing of planetary atmospheres

Infrared remote sensing is a powerful tool for studying the chemical composition and the thermal structure of planetary atmospheres. Infrared spectra, in particular, are used to derive molecular abundances and to infer elemental and isotopic ratios, which allow to constrain theoretical models of the formation and early evolution of the solar system, as well as the history of planetary atmospheres. Infrared imaging and spectroscopy have been performed from the ground but also from space planetary missions (Mariner 9 on Mars, Voyager on the giant planets, Galileo on Jupiter), and from the ISO Earth-orbiting infrared satellite. In the forthcoming decade, the Cassini mission will explore the Saturn system. Planetary exploration from Earth orbit will be performed by the FIRST and NGST space observatories.     

火星车载激光诱导击穿光谱仪(MarsCoDe)在轨定标样品选取研究

我国首次火星全球遥感与区域巡视探测任务已获批立项,首个火星探测器也即将前往火星。为满足火星物质成分分析的需求,我国研制了不同类型的火星物质成分分析仪器,其中包括火星表面成分探测仪（MarsCoDe）,应用了激光诱导击穿光谱技术（laser-induced breakdown spectroscopy,LIBS）。火星表面覆盖尘埃,探测仪器想要准确获取火星尘埃之下的物质成分,必须剥去尘埃或者进行破坏从而深入岩层取样。LIBS可以用激光烧蚀待测物体表面,获得深部物质光谱信息,在火星表面探测中具有其他仪器无法取代的优势。LIBS在火星探测中几乎适用于探测每一个元素,包括轻元素H,Li,Be,B,C,N,O等,帮助寻找有机物和含水地质过程的证据。由于LIBS在火星环境工作,等离子体的物理性质与地球上完全不同。为了确保火星车载LIBS返回数据的光谱质量,需要对LIBS在着陆后开展在轨定标。借助火星车的携带在轨定标样品,对探测数据进行在轨定标,确保返回数据的可靠性。定标样品的选择是一项十分重要的工作,存在仪器工程条件限制、定标样品类型的代表性、元素成分分布范围、样品稳定性等多种考虑因素,需满足科学任务的同时达到加工工艺要求。总结了国外已有的火星车载LIBS在轨定标的研究进展,重点分析了LIBS在轨定标样品选择依据、国外选择样品的优缺点,并总结经验提出了几点建议,为我国在轨定标工作提供参考。对火星探测数据的正确解译,对未来研究火星的起源、火星的长期地质演变过程等具有重要的科学意义。     

火星探测可见光遥感相机的发展现状与趋势

介绍了近些年来国际上几个主要的火星探测遥感相机,包括美国的火星观测相机（Mars Observer Camera,MOC）、高分辨率科学成相试验相机（High Resolution Science Imaging Experiment,HiRISE）,以及欧空局的High Resolution Stereo Camera（HRSC）的发展概况、主要技术指标和技术特点,指出遥感器应具备近红外成像和三维立体成像功能,开展亚米级分辨率精细观测是今后火星遥感探测的主要发展趋势。本文还探讨了不同目标观测对成像分辨率的要求。通过对发展现状的调研和科学需求的分析,为我国今后开展火星可见光遥感观测提供了指标选择和设计的依据。     

Applications of same-beam VLBI in the orbit determination of multi-spacecrafts in a lunar sample-return mission

Same-beam VLBI means that two spacecrafts with small separation angles that transmit multi-frequency signals specially designed are observed simultaneously through the main beam of receiving antennas. In same-beam VLBI,the differential phase delay between the two spacecrafts and the two receiving antennas can be obtained within a small error of several picoseconds. As a successful application,the short-arc orbit determination of several hours for Rstar and Vstar,which are two small sub-spacecrafts of SELENE,has been much improved by using the same-beam VLBI data together with the Doppler and range data. The long-arc orbit determination of several days has also been accomplished within an error of about 10 m with the same-beam VLBI data incorporated. These results show the value of the same-beam VLBI for the orbit determination of multi-spacecrafts. This paper introduces the same-beam VLBI and Doppler observations of SELENE and the orbit determination results. In addition,this paper introduces how to use the same-beam VLBI for a lunar sample-return mission,which usually consists of an orbiter,a lander and a return unit. The paper also offers the design for the onboard radio sources in the lunar sample-return mission,and introduces applications of S-band multi-frequency same-beam VLBI in lunar gravity exploration and applications during all stages in the position/orbit determinations such as orbiting,landing,sampling,ascending,and docking.     

Multispectral imaging of Mars: ISM results

Summary Multispectral imaging of planets opens a new class of studies of atmospheric and surface signatures. With ISM experiment on board Phobos, the first IR multispectral imaging of Mars from space was achieved. In viem of the Future Omega experiment on board Mars 94, we present here a sample of data and results (and problems) which can be achieved by studying spectral reflectance. Paper presented at the V Cosmic Physics National Conference, S. Miniato, November 27–30, 1990.