无需初值猜测的间接法小推力轨道设计

在间接法求解小推力轨道计算中,通过先选取合适的性能指标,并对小推力最优控制问题转化为两点边值问题的方程在开普勒轨道附近线性展开,有效增强了协态变量初值收敛性,使得该方法无需对协态变量初值进行反复的随机猜测,迭代过程也不需要人工干预,提高了轨道搜索应用中的计算效率.之后再对性能指标进行迭代优化,可获得逼近于Bang-bang控制的控制方案.     

单位矢量法的数学模型(MMUVM)及其简化形式(PUVM1)的迭代法的收敛性

利用人造地球卫星观测资料测定有摄初轨的单位矢量法(PUVM1),已得到了非常广泛地实际应用.为了对单位矢量法作进一步地完善和改进,首先在考虑测量误差模型的基础上,建立单位矢量法所对应的数学模型MMUVM.它本质上就是一个非线性最优化问题.针对MMUVM,先分别使用多圈仿真数据和实测数据,形成了与之相对应的目标函数,再利用求解最优化问题的一种三对角二次插值模型的直接搜索方法,分别对其进行了数值处理.计算结果表明,所建立的优化模型MMUVM正确合理,所采用的直接搜索方法实用有效.其次,进一步指明了PUVM1和MMUVM之间关系,即:从本质上讲,PUVM1就是MMUVM的一种简化形式.从数学原理上,清楚地解释了利用PUVM1的准法化方程,只能使用单圈短弧段数据进行初始轨道确定,而不能使用长弧段多圈资料进行轨道确定或轨道改进的根本原因.最后,对PUVM1的迭代算法的收敛性问题进行了初步的理论分析,并给出了相应的数值验证实例,指出了PUVM1的迭代格式是条件收敛的,即:只有在满足一定条件后,才能收敛.这也就意味着:有的时候,尽管准法化方程是合情合理的,但是,此时该迭代法却是发散的,无法迭代求出所要的解.     

人造卫星观测的周日光行差的改正

本文讨论了人造卫星观测中卫星位置与测站位置所对应的时间不一致问题,证明了,对于方向观测,这种改正等价于卫星视位置到真位置的周日光行差的改正,并给出了其它观测的改正公式。经过这些改正后,在轨道改进时,星历表计算就可用最简单的时间对应的公式计算,不必进行迭代,也无需加任何附加项。     

利用3次方位观测天基初轨确定新方法

提出了一种适用于天基空间目标光学观测的初始轨道确定新方法. 通过对比地基和天基观测的几何构型, 分析了利用天基光学观测数据进行初轨确定时计算收敛到观测平台自身轨道的原因. 基于轨道半通径方程和改进Gauss方程, 推导出了斜距条件方程组的解析形式, 将天基光学观测的初轨确定问题转换为求解关于观测时刻斜距变量的非线性条件方程组的问题. 利用轨道能量约束减小了解的搜索区域, 消除了方程组的奇点. 最后利用天基实测数据验证并分析了非线性条件方程组根的性质, 利用低轨光学观测平台对低、中、高轨和大椭圆轨道空间目标的仿真观测数据验证了方法的有效性.     

小行星(215)、(323)、(416)和(432)的轨道改进

这四颗小行星的历元很早,都是在二、三十年以前.由于多年未算摄动,轨道逐渐偏离,观测与计算间差值。O—C 已增大到一度以上.鉴于改进轨道、计算准确冲日星历表的迫切需要,1962年冬季在已利用电子计算机算得木星、土星精确摄动的基础上,我们搜集了近几年的观测资料,对此四颗星作了轨道改进.轨道改进的计算系根据爱克尔和勃劳威尔(Eckert and Brouwer)的直角座标的方法.为避免小偏心率和大倾角情况对精确度的影响,使能比较确定地求得方程式的解,我们采用下列方程系统:     

基于Broyden方法的不对称与对称周期解延拓算法与应用

考虑周期解的数值延拓问题并提出基于Broyden拟牛顿法来延拓周期解的一种有效算法,先后以布鲁塞尔振子、平面圆型限制性三体问题(Planar Circular Restricted Three-Body Problem, PCRTBP)的周期解为例进行了验证.这里的Broyden方法包含线性搜索、正交三角分解求线性方程组的步骤.对一般的周期解,周期性条件方程组中含有周期作为待延拓参数,可用周期来决定积分时长,将解代入周期性条件得到积分型的非线性方程组,利用Broyden方法迭代延拓直至初值收敛.根据两次垂直通过一个超平面的轨道是对称周期轨道的性质,可采用插值的方法求得再次抵达超平面的解分量,得到周期性条件方程组,再用Broyden方法求解.结合哈密顿系统的对称性和PCRTBP周期轨道的一些分类,对2/1、3/1的内共振周期解族进行了数值研究.最后,对算法和计算结果做了总结和讨论.     

自由段弹道识别及快速预警

针对地面预警雷达捕获跟踪空间目标和实时测轨获取的目标轨道根数,提出了一种基于目标轨道运动特征识别自由飞行导弹及推算发点、落点的处理方法.该方法分为二体模型求解初交点和摄动修正两部分,分别进行迭代计算.数值实验结果表明:该处理方法计算收敛速度快,每次仅需6~8次迭代,能够满足导弹预警的高时效性要求.     

稳健估计在轨道改进中的应用

通过对20颗卫星的模拟计算，研究了人造卫星光学观测的轨道改进方法，给出了资料预处理(观测精度σ0=5″)的剔除门限，使野值的比例在大多数情况下小于10％；在轨道改进中，先用Huber估计迭代2次，再用Hampel估计迭代到收敛，保证了轨道改进的精度；重点研究了Hampel估计的权函数参数(C0，C1，C2)的取值，得出结论：对于大于或等于6σ0的野值，C0可取为2．2，C1可取为3．6，C2的取值和野值大小有关．     

小行星钟山1号、钟山2号

1974年冬,我们在使用400/3000双筒镜进行的观测工作当中,发现了一些小行星.其中有两颗小行星,轨道近日距较小,轨道倾角较大.发现的时候,正当它们大冲之后,比较靠近地球,显现出颇为快速的视运动.对这两颗星,我们分别追踪得到14次与7次观测,均各有五十多天的弧长.现将观测数据和据此计算出的轨道根数列表于后.     

一种适用于大偏心率轨道密集星历精密计算的快速处理方法

空间目标探测和编目是航天器安全的重要课题, 空间目标数量巨大, 造成轨道计算的工作量十分繁重. 分析方法虽然计算速度快, 却不能适应高精度观测资料的处理工作, 因而数值方法将成为目标轨道计算的重要方法. 空间目标编目工作普遍涉及密集星历的产生和计算问题, 针对这一问题的大偏心率轨道数值计算目前尚未形成兼具计算精度和计算效率的有效技术手段, 难以满足编目工作的处理要求. 在此背景下, 提出一种适用于大偏心率轨道密集星历精密计算的快速处理方法, 并通过数值实验对模型参数进行优选, 最后通过计算实例证实了该计算方案的优越性.     

Online application for the barometric coefficient calculation of the NMDB stations

The primary processing of the neutron monitor data includes all the necessary actions and procedures that each cosmic ray station follows in order to provide the worldwide neutron monitor network with good quality data. One of the main corrections of the primary data is the pressure correction due to the barometric effect. The barometric effect induces variations to the measured data of the neutron monitors which are related to the variations of the local atmospheric pressure of the stations. This correction requires the definition of the barometric coefficient which is calculated experimentally. The accurate calculation of the coefficient is a prerequisite for the quality of the data. This paper presents the implementation of an online tool which calculates the barometric coefficient of a cosmic ray station, by taking advantage of the fact that most stations publish their data on the Neutron Monitor Data Base.     

基于图像的天体搜索研究与自动化集成软件开发

天体搜索是天文数据处理流程的一个重要环节,也是以平方公里阵列射电望远镜(Square Kilometre Array, SKA)为代表的下一代射电望远镜在面向海量数据处理中的挑战之一.现今天体自动搜索算法、软件已日趋成熟并投入应用,不过在自动化、兼容性等方面仍具有提升空间.以更自动化、更适应海量数据需求的天体搜索算法研究为宗旨,以现有算法为研究基础,天体自动搜索软件系统得到设计和开发.该系统包含友好的交互式用户操作界面,具备可视化输出数据显示、兼容不同数据输入和输出并包含为实际应用服务的文件管理功能.该系统对于大天区图以及图像集,均能够很好地进行自动化处理.测试结果显示,上述方法对于天体搜索的改进有一定成效.后续将在此基础上对该集成系统做进一步的改进开发,以适应更多的需求.     

The Study on the Group Delay Jumping of CE-4 VLBI System

The phase delay software is a key component of VLBI (Very Long Baseline Interferometry) orbit determination system in CE-4 mission, which is critical to deep space exploration. When processing X-band DOR (Differential One-way Ranging) signals of probes in the past, the group delay jumping occasionally occurred in the observed scan. This paper consists of two parts. First, according to the VLBI station signal reception and VLBI center data processing steps, we analyzed the frequency, phase, power, and self-correlation spectrum of the signal, and located the influencing factor at the abnormal analog signal of Kunming (KM) station. Second, the group delay jumping was revised by the post-correction method, which was based on the analysis of the abnormal unwrap phase. We used the corrected phase to get the new group delay, and used orbit determination software to verify the effectiveness of the post-correction method, which upgraded the phase delay processing software.     

嫦娥四号VLBI群时延跳变研究

相时延处理软件是嫦娥四号(CE-4)任务甚长基线干涉测量(Very Long Baseline Interferometry,VLBI)测轨分系统软件配置项之一,利用其处理着陆巡视器X波段DOR(Differential One-way Ranging)信号时,观测弧段(scan)内偶尔存在残余群时延跳变问题.论文主要分为两部分:一是根据VLBI信号接收和数据处理流程,从相关相位、频率、幅度和功率方面进行分析,最终将影响因素定位在昆明测站模拟信号异常;二是以scan内时延跳变影响因素分析为基础,通过修正异常基线相关相位,研究残余群时延跳变事后改正方法,并利用定轨软件验证其有效性,升级了相时延处理软件.     

Upgraded photometric system on the 85-cm telescope at Xinglong station

The 85-cm telescope at Xinglong station is a prime focus system that operates well with high science outputs. The telescope has been upgraded since 2014 with a new corrector, and new filters and camera, which are provided by Beijing Normal University. The filter set is the Johnson-Cousins U BV RI system. We report the test results of the new system including bias, dark current, linearity, gain and readout noise of the CCD camera. Then we derive accurate instrumental calibration coefficients in U BV RI bands with Landolt standard stars during photometric nights. Finally, we give the limiting magnitudes with various exposure times and signal-to-noise ratios for observers as references.     

SHORDE I program system and applications

As one of the Analysis Centers of SLR global data, a program system named SHORDE I has been developed at Shanghai Observatory. This software package is used for processing observational data of satellites and estimating satellite orbit and dynamical and geodetic parameters. The reference systems and the force model required for constructing the package were first realized at the cm-level. In order to save running time and the storage on the computer, a multistage-multiarc procedure has been especially designed.The technique has been applied to the SLR data from LAGEOS and earth rotation parameters and precise station coordinates were derived using the data from Nov. 1984 to Jan. 1988.     

NTSC时频基准实验室守时系统自动监测软件

为了能实时了解中国科学院国家授时中心（NTSC）时频基准实验室守时系统的运转情况,编制了本软件。本软件的功能是对系统中原子钟最近一个月的比对数据进行实时计算后,得到一个纸面的加权平均时间尺度“TA”,用它作为监测UTC（NTSC）、UTC（JATC）和原子钟运转情况的参考,给出TA-UTC（NTSC）、TA-UTC（JATC）、以及每个钟相对于TA的速率曲线。通过选用窗体上设置的各个按钮,能很方便地监测原子钟和测量设备的运行情况。位于陕西蒲城的BPL监控室可以通过远程局域网得到NTSC守时实验室的数据,实时运行本软件,并用TA作为参考,即可监测BPL监控室原子钟运行情况,并且对BPL发播工作钟时间T（PU）进行监测和频率驾驭,以实现T（Pu）同步到扩形（NTSC）。     

Structure of Saturn's Mesosphere from the 28 Sgr Occultations

We analyze an extensive data set of immersion and emersion lightcurves of the occultation of 28 Sgr by Saturn's atmosphere on 3 July 1989. The data give profiles of number density as a function of altitude at a variety of latitudes, at pressures ranging from about 0.5 to about 20 μbar. The atmosphere is essentially isothermal in this range, with a temperature close to 140 K for an assumed mean molecular weight of 2.135. Owing to favorable ring geometry, an accurate radial scale is available for all observations, and we confirm the substantial equatorial bulge produced by zonal winds of ∼450 m/s first observed in the Voyager radio-occultation experiments. The fact that the bulge is still present at microbar pressures suggests that the equatorial winds persist to high altitudes. According to our radial scale, the 2.4-μbar level, which corresponds to half-flux in the stellar occultations, is at an equatorial radius of 60,960 km. This radial scale is in good agreement with the Voyager radio-occultation data at mbar pressures and allows smooth interpolation of the isothermal structure between the stellar-occultation and radio-occultation regions. We do not have such a smooth interpolation between our data and Voyager ultraviolet occultation data, unless we discard the lowest 200 km of Voyager ultraviolet data. When this is done, we obtain a complete atmospheric model from an equatorial radius of 61,500 km down to an equatorial radius of 60,500 km. This model gives excellent agreement between all 28 Sgr, Voyager, and Pioneer 11 data.     

基于粒子群优化的LAMOST初始波长定标方法

大天区面积多目标光纤光谱天文望远镜(Large Sky Area Multi-Object Fiber Spectroscopic Telescope,LAMOST)初始波长定标操作,对于在先验定标系数附近搜索解空间内的每一点,通过插值法生成对应定标系数下的虚拟定标灯谱,再将生成的虚拟定标灯谱与实测定标灯谱作互相关运算,使得相关系数最大时对应的定标系数即为初始定标结果,其实质是一个多参数寻优问题.粒子群优化是一种基于群体智能的随机全局优化算法,具有实现简单、精度高、收敛快的特点.鉴于粒子群优化的优异性能,提出一种基于粒子群优化的LAMOST初始波长定标方法,并设计相应算法和测试实验.实验结果表明,基于粒子群优化的LAMOST初始波长定标在收敛性、解的质量、运行时间等方面都优于基于改进遗传算法参数寻优方法.     

Coordinate systems and lunar observing station positions

Satellite geodesy has yielded the locations of more than fifty stations in a single coordinate system referred to the Earth's center of mass with accuracies in the five to ten meter range. The following different methods have been used at Goddard to accomplish this.Dynamical solutions have been obtained for the locations of some fifty key stations using data from the GEOS satellite program. The distribution of observations about the stations is illustrated in terms of the data obtained for a typical station such as the one at Edinburg, Texas. Geopotential coefficients were held fixed in these solutions. The results of these dynamical determinations implied geodetic datum shifts which were then used to arrive at positions for some two hundred additional stations.Another approach involved the adjustment of the coordinates of seventeen stations on the basis of observations of short arcs of GEOS satellite orbits. These results were found to be consistent with those obtained through ground surveys to about five meters rms in each coordinate.Simultaneous solutions for station locations and geopotential coefficients have also yielded values for positions of some sixty stations, again in a coordinate system defined in terms of the Earth's center of mass.Lunar laser ranging and lunar occultation observing programs involve knowledge of the positions of the observing sites. In some cases the lunar observing program itself yields station coordinate information. In other cases greater reliance is placed upon independent determinations of site locations. The location of an occultation observation site at Olifantsfontein, for example, has been obtained in a center-of-mass system in both the dynamical and simultaneous satellite solutions. It is anticipated that a dynamical satellite solution will be extended in 1973 to obtain center-of-mass coordinates for a station in New Zealand. This will make it possible to tie an occultation site in that region to a dynamically determined coordinate system referred to the mass center. Coordinates for stations at Organ Pass, New Mexico, determined in both the dynamical and simultaneous solutions, and Edinburg, Texas, found in both the dynamical and short-arc adjustments, provide the basis for referring the location of a facility such as the McDonald Observatory to a center-of-mass system either through accurate ground surveying techniques or by means of a satellite geodesty tie. The latter approach has already been used, for example, to fix the position of an isolated site on Madagascar relative to a reference point in Africa and, in turn, to a center-of-mass coordinate system.Estimates of the accuracies of the satellite determinations are discussed.Theoretical aspects of coordinate systems associated with the Earth and the Moon are also considered.Communication presented at the conference on Lunar Dynamics and Observational Coordinate Systems held January 15–17, 1973 at the Lunar Science Institute, Houston, Tex., U.S.A.