DTM94大气模型及其应用

简述了ＤＴＭ９４大气模型,并以其旧版本ＤＴＭ７８为对照进行了初步考察和分析,其中给出了两种模型的大气密度随地磁指数ｋｐ,和太阳辐射流量（ＳｏｌａｒＲａｄｉｏＦｌｕｘ）变化的情况,并对２０ｄ（天）弧长Ａｊｉｓａｉ卫星的全球ＳＬＲ观测资料进行处理,结果表明ＤＴＮ９４对近地卫星Ａｊｉｓａｉ的精密定轨是十分有利的。     

关于J77大气模型用于Ajisai卫星定轨的讨论

当对近地卫星进行定轨时,将不可避免地遇到选取大气模型的问题,这些模型包括指数模型（ＥＸＰＴ）ＤＴＭ、ＣＩＲＡ８６和Ｊ７７等模型。而Ｊ７７是较后形成的模型,它在大气阻力的研究中往往备受关注。这时,作者将涉及如何解决在ＶＡＸ３８００计算机上用Ｊ７７大气模型来处理Ａｊｉｓａｉ卫星资料时所遇到的计算发散问题,分析计算结果后,发现定轨软件ＳＨＯＲＤＥ中参数的选取不当是造成计算发散的根本原因,同时,我们给出了     

关于J77大气模型用于Ajisai卫星定轨的讨论(英文)

当对近地卫星进行定轨时,将不可避免地遇到选取大气模型的问题,这些模型包括指数模型（ＥＸＰＴ）、ＤＴＭ、ＣＩＲＡ８６和Ｊ７７等模型。而Ｊ７７是较后形成的模型,它在大气阻力的研究中往往备受关注。这里,作者将涉及如何解决在ＶＡＸ３８００计算机上用Ｊ７７大气模型来处理Ａｊｉｓａｉ卫星资料时所遇到的计算发散问题,分析计算结果后,发现定轨软件ＳＨＯＲＤＥ中参数的选取不当是造成计算发散的根本原因,同时,我们给出了该参数的建议值为１０－１２。最后,将Ｊ７７的结果与其它模型的结果相比较,表明参数的调整是有效的。     

Starlete卫星精密定轨中大气模型效度的比较

为满足大气模型比较的需要，把ＣＩＲＡ－１９８６大气模式（简称ＣＩＲＡ８６）引入大气阻力选择模块，对上海天文台人造卫星精密定轨软件ＳＨＯＲＤＥ［１］进行大气模式的扩充。利用多种大气模式分别对Ｓｔａｒｌｅｔｅ卫星的观测资料进行解算，结果表明：ＳＨＯＲＤＥ中指数大气模式更适合对Ｓｔａｒｌｅｔｅ卫星进行精密定轨研究     

Starlette卫星精密定轨中大气模型效度的比较

为满足大气模型比较的需要，把ＣＩＲＡ－１９８６大气模式（简称ＣＩＲＡ８６）引入大气阻力选择模块，对上海天文台人造卫星精密定轨软件ＳＨＯＲＤＥ进行大气模式的扩充。利用多种大气模式分别对Ｓｔａｒｌｅｔｔｅ卫星的观测资料进行解算，结果表明：ＳＨＯＲＤＥ中指数大气模式更适合对Ｓｔａｒｌｅｔｔｅ卫星进行精密定轨研究。     

二体问题状态转移矩阵的分析解和数值解的比较

对二体问题的状态传播问题, 以Ａｊｉｓａｉ 卫星某历元的初轨为例,考虑５ｄ （ 天） 、１０ｄ （ 天） 和１００ｄ （ 天） 间隔的弧长, 本文分别给出了它们的分析解和数值解。结果表明： 对应于５ｄ、１０ｄ、１００ｄ 间隔的弧长, 二体问题状态转移的分析解与数值解在１０－１０ 、１０ －８ 和１０－７ 以内的相对偏差下能够保持其一致性。     

二体问题状态转移矩阵的分析解和数值解的比较

对二体问题的状态传播问题,以Ａｊｉｓａｉ卫星某历元的初轨为例,考虑５ｄ（天）,１０ｄ（天）和１００ｄ（天）间隔的弧长,本文分别给出它们的分析解和数值解,结果表明：在应于５ｄ,１０ｄ,１００ｄ间隔的弧长二体问题状态转移的分析解与数值解在１０＾－１０,１０＾－８和１０＾－７以内的相对偏差下能够保持其一致性。     

GEOSAT GM的精密轨道确定及精度估计

对最近公开的ＧＥＯＳＡＴ ＧＭ期间的ＴＲＡＮＥＴ Ｄｏｐｐｌｅｒ数据作了分析,利用这些数据和新的ＪＧＭ３重力场模型,计算了ＧＥＯＳＡＴ在ＧＭ期间的精密历元．９１个６天弧解给出的平均的Ｄｏｐｐｌｅｒ残差为４．３ｍｍ／ｓ,估计出所计算的轨道径向精度约为１０ｃｍ。     

低质量AGB星重元素的核合成

本文以（１３）Ｃ（α，ｎ）（１６）Ｏ作为中子源，考虑到恒星核心质量随热脉冲数的变化及星风、超星风质量损失的影响，采用从（５６）Ｆｅ到（２１０）Ｂｉ的无分支ｓ过程反应通道，拟合了ＭＳ、Ｓ的重元素超丰．本文特别将恒星质量与ＡＧＢ内Ｓ过程核合成模型结合起来讨论．结果表明质量较大的恒星因对流较强而稀释因子较大，ＭＳ、Ｓ星在轻、重Ｓ元素丰度关系图中分别落入四个不同区域，由此可以粗略估计这些恒星的质量．２．５Ｍ　的ＡＧＢ星形成具有环状空腔的星体，最后演化成Ｔｃ—ｎｏ单星，可以解释双星系统伴星为主序星的ＡＧＢ星无Ｔｃ现象．     

用ASM／RXTE数据对Crab天区的直接解调成像

利用对象重建的直接解调技术,对ＡＳＭ／ＲＸＴＥ的模拟数据和Ｃｒａｂ天区观测数据进行了成像分析。结果表明,借助于对象重建的直接解调技术,可以利用正在运行的Ｘ射线天卫星ＲＸＴＥ上的全天监测器ＡＳＭ实现硬Ｘ射线天空的成像。     

基于SLR精密轨道的天文定位精度分析

利用全球卫星激光测距服务系统(ILRS,International Laser Ranging Service)标准点资料对Ajisai卫星进行精密定轨,残差均方根(RMS)优于3 cm,得到该星的精密轨道.进而对长春站40 cm空间碎片光电望远镜获得的Ajisai卫星的天文定位资料进行精度分析,外符合精度约3″左右.单独利用天文定位数据进行轨道改进,内符合精度优于3″.改进轨道的x、y、z坐标3分量在观测数据覆盖范围内的精度在100 m之内.同样地对Jason-1卫星作数据分析,结果和Ajisai卫星精度相当.分析各个弧段的精度变化,发现定标星个数减少,会导致天文定位精度下降.据此提出可以把最少定标星比例作为评定数据质量的参考指标之一.     

TLE-Aided Orbit Determination Using Single-Station SLR Data

It is difficult to use the single-station satellite laser ranging (SLR) data for orbit determination, due to the singular geometrical distribution of the observations. The single-station data produced by performing the diffuse- reflection SLR on the earth-orbiting space debris are therefore ineffective for orbit improvement. To solve this problem, we propose an orbit determination method by using single-station SLR data in aid of the two-line element set (TLE). For verifying its feasibility, this method is implemented and applied to the orbit determination of the satellite Ajisai, using the single-station SLR data of five passes in one day and the corresponding TLE. And on this basis, the five-day orbit prediction is generated, the result indicates that the errors of predicted positions are less than 40 m. In addition, the potential application of this method in the orbit improvement of space debris is discussed.     

The Accuracy of Atmospheric Models in Solar Maximum Years Checked with the Data of CHAMP Accelerometer

A method of processing the data obtained with the CHAMP satelliteborne accelerometer is introduced. Through an analysis of the data the fault in the x-axis of the instrument is verified. We examined the accuracy of the atmospheric models in solar maximum years with the accelerometer data obtained from 2001 to 2002 and the inversion of the atmospheric density from the tangential non-gravitational acceleration. Then from a statistical analysis of the errors of the models, DTM94 and MSIS90, we obtained the following quantitative conclusions. During the solar maximum years the error of DTM94 is 30% to 35%, and that of MSIS90 is smaller at 25% to 30%. The greatest difference between the two models is about 10%.     

两行根数辅助的SLR单站定轨

单站测距资料定轨的困难限制了漫反射SLR(Satellite Laser Ranging)测距资料的应用.为此,提出利用两行根数模拟多站SLR测距资料作为辅助,实现单站SLR测距资料定轨的方法.该方法对卫星Ajisai单站SLR测距资料定轨并生成5 d预报轨道,误差小于40 m,实现利用单站测距资料的轨道改进,验证了方法的可行性.     

大气模式动态测定的研究

利用12万组大气阻力资料，对DTM－1994模式进行改造，获得了一个新的大气模式，该模式的特点是：1．利用2阶周日峰效应，代替了原来模式中的复杂的周日效应表达式，减少了模式参数（少于50个），并使模式参数均具有明确的物理意义，2．分清了模式的主要参数和次要参数，在主要参数中，又分清了利用了阻力资料可以改进的参数和可能改不好的参数．3．与MSIS－1990和DTM－1994模式相比，其互差可以被接受，说明使用卫星阻力资料可以进行大气模式动态改正，不仅能测定大气总密度，并且能测定大气的分密度，4．与卫星轨道相比较，改进有显优于MSIS－1990模式，在120km轨道附近，改进模式密度比MSIS－1990模式大10％，同时我们在卫星陨落期预报中发现，MSIS－1990模式密度比实际大气密度小9％，这说明改进模式的密度与实际大气的密度基本接近。     

Models for planetary eclipses of the uranian satellites

A model for computing the brightness of a satellite in the shadow of a planet is described, which takes into account the Sun–planet–satellite–sensor geometry, the satellite bi-directional reflectance function, and the refraction of sunlight in the planetary atmosphere. Synthetic light curves for eclipse ingress or egress of the five large satellites of Uranus are generated. The model luminosities can be fitted to photometric observations in order to calculate a precise distance between the centers of the satellite and the planet. Alternately, when the satellite ephemeris is accurately known the atmospheric state of the planet can be studied.     

大气指数模型与探空资料分析的比较─关于广州地区大气层对GPS信号时间延迟问题研究之一

ＧＰＳ系统是现阶段功能最全、精度最高的卫星导航系统，大气层对ＧＰＳ系统定位和定时的影响已成为一个不可忽略的重要因素．本文从广州地区两天各两个时刻的气象探空资料中分析了各个时刻高空中几个已知高度点的折射指数，然后用线性处理的办法得到了１７ｋｍ范围左右高空中折射指数的模型，大气指数模型与此模型相比较，几个点折射指数的均方差很小，最后用这两种模型分别计算两天各两个时刻大气层对ＧＰＳ信号在垂直传播时所引起的附加时间延迟，二者之差最大不大于０．３ｎｓ，用指数模型可基本反映广州地区大气层对ＧＰＳ信号传播时间延迟的影响。     

Comparison of the FLUKA calculations with CAPRICE94 data on muons in atmosphere

In order to benchmark the three-dimensional calculation of the atmospheric neutrino flux based on the FLUKA Monte Carlo code, muon fluxes in the atmosphere have been computed and compared with data taken by the CAPRICE94 experiment at ground level and at different altitudes in the atmosphere. For this purpose only two additions have been introduced with respect to the neutrino flux calculation: the specific solar modulation corresponding to the period of data taking and the bending of charged particles in the atmosphere. Results are in good agreement with experimental data, although improvements in the model are possible. At this level, however, it is not possible to disentangle the interplay between the primary flux and the interaction model.     

Stochastic Models of Hot Planetary and Satellite Coronas

The hot planetary and satellite coronas are populated by the suprathermal particles produced in the transition region between the collision-dominated and free-molecule atmospheric layers under the external effects of electromagnetic and corpuscular solar radiation and magnetospheric plasma. We construct a numerical stochastic model to investigate both the local formation and kinetics of suprathermal particles and their transport to exospheric heights from underlying atmospheric layers. In contrast to other commonly used approaches, the suggested numerical model is suitable for studying the flows of atmospheric gas weakly and strongly perturbed by suprathermal particles, i.e., for studying the formation of hot planetary and satellite coronas proper. Highly efficient Monte-Carlo algorithms with weighted particles underlie the numerical implementation of the model. This numerical model is used to investigate the following: (i) the hot oxygen corona of Europa, a Jovian satellite, which is an example of a highly nonequilibrium near-surface atmosphere; and (ii) the nonthermal losses of nitrogen from Titan, a Saturnian satellite, when suprathermal atoms and molecules of nitrogen are only a small admixture to the surrounding thermal molecular nitrogen—the main atmospheric component of Titan.