小行星初轨计算的Fortran程序设计

由改进的Laplace和Gauss方法分别给出小行星初轨计算的程序,通过两程序的比较测试得出结论——两方法适用于三次长时间间隔的角观测资料。为实现一天内角观测资料的小行星初轨计算与位置预报,对改进的Laplace方法流程进行了调整。通过增加迭代方程右矩阵的调整,预报结果可用于指导小行星的跟踪观测,文中给出调整后的流程图及预报效果数值验证。     

掩星软件OCCULT使用指南（二）

（接上期） 小行星掩星 此程序可以计算小行星、行星和其卫星掩星的预报,预报的结果可以在屏幕上直接显示出来,也可以直接打印或存到文件中。在计算之前,我们首先需要更新小行星轨道根数,有两种方法：一是使用软件自动下载更新（你的电脑里需要安装FTP软件）,使用软件自动下载更新方法如下：     

倾角函数展开及其在分析法轨道预报中的应用

田谐项摄动是分析法轨道预报中的重要部分,其中包含大量倾角函数及其偏导数的计算.由于具有精度更高、速度更快的优点,倾角函数一般通过递推方法计算.以文献中提出的改进Gooding方法为基础,将其给出的程序稍加改进,在计算2–50阶倾角函数时缩短了约24%的计算时间.考虑到分析法预报过程中轨道平倾角变化很小,以泰勒展开式计算倾角函数,可极大提高计算速度,较大程度地减小分析法预报耗时,且引力场阶次越高,减小幅度越大,取50阶时预报耗时缩短了48%.另一方面,以2阶展开式计算倾角函数时,与改进Gooding法相比,分析法预报星历偏差很小.对于500 km高度的低轨卫星,分别以改进Gooding法和2阶泰勒展开式计算倾角函数,预报3天,当地球引力场阶次不高于50时,二者预报星历偏差RMS (Root Mean Square)低于1 mm,且随着轨道高度的增加,预报星历偏差RMS逐渐减小.     

卫星轨道预报的一种分析方法

人造地球卫星的轨道预报是空间环境监测和实时跟踪测量中一个重要环节，由于监测对象众多，要求精度也不太高，通常采用分析法预报．在已有分析法得到t时刻平均根数的基础上给出一种轨道预报方法，由t时刻的平均根数给出该时刻卫星的位置和速度，在此基础上将地球非球形引力摄动的周期项直接用卫星直角坐标的位置和速度分量表示，这样可以避免在计算轨道根数变化的周期项时出现的奇点问题，从而对根数的选择无特殊要求，可适用于各种轨道，简化预报程序和相应的软件，提高预报效率。     

应用神经网络技术预报海表温度变化异常

介绍了神经网络技术在时间序列模拟和预报中的应用要点;应用神经网络技术对Nino3.4海区海表温度变化异常(SSTA)进行了实验预报,每次给出1～12个月预报值;将预报值与SSTA实测值以及其它模型的预报值进行了比较。结果表明,在1990年1月～2007年10月期间,SSTA预报值与实测值的均方误差为±0.76℃。将2004年10月～2007年10月期间该方法的预报结果与美国气候预测中心(CPC)发布的各种模型的预报结果(只给出第2～10月预报值)进行比较,结果表明这一期间该方法预报值相对实测值的均方误差为±0.86℃,精度略好于另外一个神经网络模型的预报精度(±0.98℃)。     

太阳活动预报中的模糊识别综合指数

在太阳活动预报中,预报因子的选取和处理对预报效果影响甚大。本文在云台原有的平均综合指数基础上,运用模糊识别方法,给出了一种模糊识别综合指数,它能更好地表征太阳日面活动区的活动特征。这种方法简单、方便,较充分地利用了预报因子中所含有的有用信息,从而使识别预报率有所提高。     

法国默东太阳预报中心介绍

笔者自1984年春末至同年初冬应邀在法国巴黎—默东天文台太阳行星部工作了半年多。任务是参加设在这里的默东太阳预报中心的太阳预报工作。在与法国同行共事的时间里,对默东太阳预报中心的预报工作,包括预报的科学依据,预报方法与技术,资料来源,预报效果,设备等,有了一些了解,现在整理出来,供有兴趣者参考。     

基于修正线性组合模型的原子钟钟差预报

原子钟钟差预报在时频工作中起着重要作用.目前常用的预报模型各有优缺点,为了综合各种预报模型特点,可以考虑组合这些模型预报的结果.针对线性组合模型预报钟差时存在的问题,提出了学习权的概念,以有效地利用各种精度信息,建立了修正组合预报模型.为了验证该方法的有效性,选取了4颗GPS卫星IGS(International GN...     

二十一周峰年太阳活动预报总结

本文对二十一周峰年期间的太阳活动预报效果进行了检验,并且概述了预报方法。     

基于混沌时间序列的Volterra自适应滤波极移预报方法

针对极移复杂的时变特性, 根据混沌相空间坐标延迟重构理论, 提出一种基于Volterra自适应滤波的极移预报方法. 首先, 利用最小二乘拟合算法分离极移序列中的线性趋势项、钱德勒项和周年项, 获得线性极移、钱德勒极移和周年极移的外推值; 其次, 通过C-C关联积分法对最小二乘拟合残差序列进行相空间重构, 并利用小数据量法计算残差序列的最大Lyapunov指数验证其混沌特性, 在此基础上, 构建Volterra自适应滤波器对残差序列进行预测; 最后, 将线性极移、钱德勒极移和周年极移的外推值以及最小二乘拟合残差的预测值相加获得极移最终预报值. 利用国际地球自转服务局(International Earth Rotation and Reference Systems Service, IERS)提供的极移数据进行1--60d跨度预报, 并将预报结果分别与国际地球定向参数预报比较竞赛(Earth Orientation Parameters Prediction Comparison Campaign, EOP PCC)结果和IERS A公报发布的极移预报产品进行对比, 结果表明: 对于1--30d的短期预报, 该方法的预报精度与EOP PCC最优预报方法相当, 当预报跨度超过30d时, 该方法的预报精度低于EOP PCC最优预报方法, 优于参与EOP PCC的其他方法; 与IERS A公报相比, 该方法的短期预报效果较好, 当预报跨度增加时预报精度低于IERS A公报. 预报结果表明该方法更适合于极移短期预报.     

Sunspot intensity observations during the 9 May 1970 Mercury transit

The intensity of a sunspot was measured in eight wavelength regions during the Mercury transit of 9 May 1970. The observations have been corrected for scattered light in the Earth's atmosphere as well as in the instrument using two different methods plus a combination of these. One method consists of using Mercury as a calibration spot. In the second method the corrections for scattered light are determined from solar limb observations.     

Isophotometric measurements of Mercury

Isophotometric measurements have been made on films, taken during the transit of Mercury, on May 9, 1970. This note gives the isophotes of Mercury in front of the sun in white light and some results of the comparison between the intensity of the sunspot's umbra and Mercury in H-alpha and white light.     

The effect of scattered light on solar intensity observations as derived from 9 May, 1970 Mercury transit

The method for correcting observed sunspot intensities for scattered light has been tested using the transit of Mercury. It is found that the correction method of Zwaan (1965), Staveland (1970) has an uncertainty (rms value) of 0.05 times the photospheric intensity. During good observing conditions the uncertainty is 0.02 (rms value) with the scanning speed used in this study. A simpler and quicker correction method is suggested.Observations during Mercury's occultation of a sunspot as well as measurements close to the solar limb are briefly described.     

Correction of solar observations for stray light by numerical integration,with application to Mercury's drop

A numerical method for correction of stray light in solar observations has been developed. In particular a regular sunspot, where the circular contours of penumbra and umbra are projected as ellipses, has been studied. When a specified set of values for the stray light parameters is given, and also tentative values for the relative intensities of penumbra and umbra, the integration of stray light can be performed in any point. The result will be the observable intensity if the conditions were as given by these initial values.By means of limb observations the stray light parameters may be improved, and finally a variation of the penumbra- and umbra intensities in the computation, enables a determination of these quantities by comparison with observations.The method is tested on observations of the transit of Mercury, May 9, 1970. Calculation of isophotes with Mercury close to the limb shows the black drop phenomenon; which thus may be explained as an effect of stray light only.It is also shown that the Wilson effect on a sunspot cannot be produced by stray light alone.     

A Constant Elevation Search Method for Narrow Beam Radar to Capture Space Targets

Position prediction is the basis of guiding radar to seek, capture, and track space targets, although there’s a risk of insufficient accuracy for narrow beam radar due to the influence of orbit determination and propagation error. Since the along-track error is the main factor that affects the accuracy of position prediction, this paper proposed a Constant Elevation Search (CES) method for narrow beam radar, based on the idea of along-track error compensation, to seek and capture transit targets. With along-track error estimation, all possible positions on a specified elevation can be observed, thus the success rate of capturing transit targets will be improved. Simulation shows that when the position prediction method fails, the CES method still works.     

一种适用于窄波束雷达捕获空间目标的等仰角搜索方法

点位预报作为引导雷达寻找、捕获、跟踪目标的基础, 受定轨误差及预报误差的影响, 其精度对窄波束雷达存在不足的风险. 由于沿迹误差是影响点位预报精度的主要因素, 基于沿迹误差补偿的思路, 提出了一种适用于窄波束雷达的过境目标等仰角搜索方法, 在预估的沿迹误差范围内对目标一次过境时在指定仰角上可能出现的所有位置做遍历观测, 从而提高雷达捕获空间目标的成功率. 仿真算例表明, 当点位预报失效时, 等仰角搜索方法仍然能观测到目标.     

Observations of 1970 May 9 Mercury transit

During the 1970 May 9 Mercury transit on the solar disk, the Rome Astronomical Observatory performed various direct and spectroscopic observations of the apparent diameter of the planet, the instant of its third contact, the position angles of egress, and the least distance from the sundisk center. Independent methods were used for diameter determination: photometry, isodensitometry, dark calibrated disks, and photometric observations through a diaphragm closing on the planet's image. The maximum deviation among the different determinations is not larger than 0.37″ of arc; the mean weighted value gives a Mercury diameter at 1 a.u. of 6.74″ with an uncertainty of 3.8%. Also observed was a deformation phenomenon on the solar limb near the third contact: its value is estimated as 2.2″ but is not definitive.     

An on Orbit Determination of Point Spread Functions for the <Emphasis Type="Italic">Interface Region Imaging Spectrograph</Emphasis>

Using the 2016 Mercury transit of the Sun, we characterize on orbit spatial point spread functions (PSFs) for the Near- (NUV) and Far- (FUV) Ultra-Violet spectrograph channels of NASA’s Interface Region Imaging Spectrograph (IRIS). A semi-blind Richardson–Lucy deconvolution method is used to estimate PSFs for each channel. Corresponding estimates of Modulation Transfer Functions (MTFs) indicate resolution of 2.47 cycles/arcsec in the NUV channel near 2796 Å and 2.55 cycles/arcsec near 2814 Å. In the short (\({\approx}\,1336~\mathring{\mathrm{A}}\)) and long (\({\approx}\,1394~\mathring{\mathrm{A}}\)) wavelength FUV channels, our MTFs show pixel-limited resolution (3.0 cycles/arcsec). The PSF estimates perform well under deconvolution, removing or significantly reducing instrument artifacts in the Mercury transit spectra. The usefulness of the PSFs is demonstrated in a case study of an isolated explosive event. PSF estimates and deconvolution routines are provided through a SolarSoft module.     

On the need for space observations of the umbra/photosphere intensity ratio

We draw attention to the possibility of distinguishing between different sunspot theories by observing: (i) The umbra/photosphere intensity ratio as a function of spot size and (ii) the morphology and time evolution of sunspot inhomogeneities such as umbral dots. In arguing the need for space observations of sunspot intensities we discuss the corrections for stray light for ground based and space observations.The opportunity to use the November 13, 1986 Mercury transit as an in situ calibration event is pointed out.Proceedings of the 14th ESLAB Symposium on Physics of Solar Variations, 16–19 September 1980, Scheveningen, The Netherlands.     

TRACE observations of the 15 November 1999 transit of Mercury and the Black Drop effect: considerations for the 2004 transit of Venus

Historically, the visual manifestation of the “Black Drop effect,” the appearance of a band linking the solar limb to the disk of a transiting planet near the point of internal tangency, had limited the accuracy of the determination of the Astronomical Unit and the scale of the Solar System in the 18th and 19th centuries. This problem was misunderstood in the case of Venus during its rare transits due to the presence of its atmosphere. We report on observations of the 15 November 1999 transit of Mercury obtained, without the degrading effects of the Earth's atmosphere, with the Transition Region and Coronal Explorer spacecraft. In spite of the telescope's location beyond the Earth's atmosphere, and the absence of a significant mercurian atmosphere, a faint Black Drop effect was detected. After calibration and removal of, or compensation for, both internal and external systematic effects, the only radially directed brightness anisotropies found resulted from the convolution of the instrumental point-spread function with the solar limb-darkened, back-lit, illumination function. We discuss these effects in light of earlier ground-based observations of transits of Mercury and of Venus (also including the effects of atmospheric “seeing”) to explain the historical basis for the Black Drop effect. The methodologies we outline here for improving upon transit imagery are applicable to ground-based (adaptive optics augmented) and space-based observations of the 8 June 2004 and 5-6 June 2012 transits of Venus, providing a path to achieving high-precision measurements at and near the instants of internal limb tangencies.