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GEOSAT及其轨道特征 总被引：2，自引：0，他引：2
赵长印 《紫金山天文台台刊》1997,16(4):239-245
本文介绍了美国的海洋测高卫星GEOSAT,分析讨论了GEOSAT的理论设计轨道及实测轨道特征。 相似文献
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本主要讨论了利用激光测月资料解算UT的两种方法：一种方法为仅仅解算世界时TU，另一种方法是同时求解UT和纬度变化△φ。经过实际计算和分析比较，结果表明：就目前的观测资料而言，只解UT的方案对解算UT值较有利。本着重讨论了在逐步回归解算中，自变量之间的相关性问题，这种情况下采用岭回归法解算，结果会有所改善。 相似文献
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极移速度的周期分析 总被引：1，自引：0，他引：1
钱昌夏 《中国科学院上海天文台年刊》1995,(16):35-40
本文对瞬时极的移动速度用自回归谱估计的Marple算法进行了周期分析，结果表明，瞬时极的移动速度可能存在着2386.天（6.5天）、1168.9天（3.2年）、321.3天、163.7天、130.1天及92.7天等6个周期，同时计算了极移的振幅和周期，发现极移的速度与极移的振幅正相关，与极移的周期负相关，并且发现厄尔尼诺现象都出现在地极移动周期较短的年份。 相似文献
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Jian-Nan Zhang A-Li Luo Yong-Heng Zhao 《天体物理学报》2009,(6):712-724
PLS （Partial Least Squares regression） is introduced into an automatic estimation of fundamental stellar spectral parameters. It extracts the most correlative spectral component to the parameters （Teff, log g and [Fe/H]）, and sets up a linear regression function from spectra to the corresponding parameters. Considering the properties of stellar spectra and the PLS algorithm, we present a piecewise PLS regression method for estimation of stellar parameters, which is composed of one PLS model for Teff, and seven PLS models for log g and [Fe/H] estimation. Its performance is investigated by large experiments on flux calibrated spectra and continuum normalized spectra at different signal-to-noise ratios （SNRs） and resolutions. The results show that the piecewise PLS method is robust for spectra at the medium resolution of 0.23 nm. For low resolution 0.5 nm and 1 nm spectra, it achieves competitive results at higher SNR. Experiments using ELODIE spectra of 0.23 nm resolution illustrate that our piecewise PLS models trained with MILES spectra are efficient for O ～ G stars： for flux calibrated spectra, the systematic offsets are 3.8%, 0.14 dex, and -0.09 dex for Teff, log g and [Fe/H], with error scatters of 5.2%, 0.44 dex and 0.38 dex, respectively; for continuum normalized spectra, the systematic offsets are 3.8%, 0.12dex, and -0.13 dex for Teff, log g and [Fe/H], with error scatters of 5.2%, 0.49 dex and 0.41 dex, respectively. The PLS method is rapid, easy to use and does not rely as strongly on the tightness of a parameter grid of templates to reach high precision as Artificial Neural Networks or minimum distance methods do. 相似文献
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2008年,对于13．2亿中国人民来说,是具有里程碑意义的一年!因为在这一年,中国将纪念拨开迷雾,摆脱无休止“文革”恶斗,终于踏上“改革开放”大道,阔步前进的30周年。 相似文献
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针对广义回归神经网络用于日长变化预报过程中,样本的输入方式对预报结果的影响进行了研究。采用2种输入方式:即样本按不同跨度输入以及按连续输入,对日长变化进行预报。最终证明不同的样本输入方式对日长变化预报精度的影响较大,样本按跨度输入在超短期预报中预报精度较高,样本采用连续输入的方式在短期和中期预报中预报精度较高。 相似文献
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LSTAR模型用于太阳黑子相对数预测的初步研究 总被引：1，自引：0，他引：1
郑大伟 《中国科学院上海天文台年刊》1993,(14):164-169
本采用了1891年至1988年期间的太阳黑子相对数的月均值资料序列，进行了用非线性时间序列分析的跳步门限自回归（LSTAR）模型作预测的研究。三年的预测结果表明，预测值与实际月均值之间的相对误差约为17％，预测值的平滑值与实际月均值的平滑值之间的相对误差接近8％左右，该方法预测的初步尝试结果表明，1992年每月的太阳黑子相对数仍将可能稳定在100以上，第22周太阳黑子相对数的谷值期将可能发生在1996年。 相似文献
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本用自回归谱的Marplc算法，对1990年发表的IERS新UT1－UTC序列进行了分析，得到了与理论值非常接近的潮汐短周期项Mf、Mm波的谱峰及财年项、半年项的谱峰，还用最小二乘法对它们进行了振幅估计，并解算了Love数K值，结果为KMf=0.305±0.040,KMm=0.303±0.062。 相似文献
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Correlation analysis of solar wind parameters, namely solar wind velocity, pro- ton density, proton temperature and mean interplanetary magnetic field (IMF) from the ACE spacecraft data near Earth, was done. To our best knowledge, this study is a novel one since we consider here only the parameters inside the solar wind, including the mean IMF and, hence, the solar wind is a self consistent system. We have proposed a Multiple Linear Regression (MLR) model for the prediction of the response variable (solar wind velocity) using the parameters proton density, proton temperature and mean IMF mea- sured as dally averages. About 60% of the observed value can be predicted using this model. It is shown that, in general, the correlation between solar wind parameters is sig- nificant. A deviation from the prediction at the solar maximum is interpreted. These results are verified by a graphical method. 相似文献
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The magnetic field is one of the most important parameters in solar physics,and a polarimeter is the key device to measure the solar magnetic field.Liquid crystals based Stokes polarimeter is a novel technology,and will be applied for magnetic field measurement in the first space-based solar observatory satellite developed by China,Advanced Space-based Solar Observatory.However,the liquid crystals based Stokes polarimeter in space is not a mature technology.Therefore,it is of great scientific significance to study the control method and characteristics of the device.The retardation produced by a liquid crystal variable retarder is sensitive to the temperature,and the retardation changes 0.09°per 0.10℃.The error in polarization measurement caused by this change is 0.016,which affects the accuracy of magnetic field measurement.In order to ensure the stability of its performance,this paper proposes a high-precision temperature control system for liquid crystals based Stokes polarimeter in space.In order to optimize the structure design and temperature control system,the temperature field of liquid crystals based Stokes polarimeter is analyzed by the finite element method,and the influence of light on the temperature field of the liquid crystal variable retarder is analyzed theoretically.By analyzing the principle of highprecision temperature measurement in space,a high-precision temperature measurement circuit based on integrated operational amplifier,programmable amplifier and 12 bit A/D is designed,and a high-precision space temperature control system is developed by applying the integral separation PI temperature control algorithm and PWM driving heating films.The experimental results show that the effect of temperature control is accurate and stable,whenever the liquid crystals based Stokes polarimeter is either in the air or vacuum.The temperature stability is within±0.0150℃,which demonstrates greatly improved stability for the liquid crystals based Stokes polarimeter. 相似文献
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At present, optical autonomous navigation has become a key technologyin deep space exploration programs. Recent studies focus on the problem of orbit de-termination using autonomous navigation, and the choice of filter is one of the mainissues. To prepare for a possible exploration mission to Mars, the primary emphasisof this paper is to evaluate the capability of three filters, the extended Kalman filter（EKF）, unscented Kalman filter （UKF） and weighted least-squares （WLS） algorithm,which have different initial states during the cruise phase. One initial state is assumedto have high accuracy with the support of ground tracking when autonomous navi-gation is operating; for the other state, errors are set to be large without this support.In addition, the method of selecting asteroids that can be used for navigation fromknown lists of asteroids to form a sequence is also presented in this study. The simula-tion results show that WLS and UKF should be the first choice for optical autonomousnavigation during the cruise phase to Mars. 相似文献
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《天文和天体物理学研究(英文版)》2015,(4):617
<正>Research in Astronomy and Astrophysics publishes original research papers and reviews on all branches of astronomy and astrophysics.Reviews are by invitation only.Important new results that require rapid publication can be submitted as a Letter(Letters must be restricted in length to 6 printed pages). 相似文献
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VLBI观测表明,TeV伽马射线Blazar(耀变体)的喷流运动视速度远小于MeV/GeV伽马射线Blazar,然而TeV伽马射线辐射流量的快速变化却要求这些Blazar的相对论喷流速度与MeV/GeV Blazar的相当.对于这一矛盾,目前有多种解释.为了检验这些模型,我们收集了VLBI对Blazar喷流运动的监测数据,样本包括86个FSRQs(平谱射电类星体)、22个BL Lac天体,共108个Blazar;从统计上研究了,该样本中各Blazar最大视速度喷流节点的位置与射电光度相关关系.结果表明,Blazar最大视速度喷流节点的位置与射电光度有较强的相关关系,随着Blazar射电光度的减小,喷流中最大视速度VLBI节点的位置到VLBI核的距离逐渐变小.这意味着,TeV伽马源(低光度Blazar)的喷流减速区距离VLBI核较近,喷流从高能辐射区到VLBI可分辨尺度已经减速,支持减速喷流模型对TeV伽马射线Blazar上述矛盾的解释. 相似文献
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《中国科学院上海天文台年刊》2011,(0)
《中国科学院上海天文台年刊》第33期(2012年)开始征稿。欢迎台内外科技工作者,把您们的科研成果、阶段性成果、观测数据分析、仪器研制、课题研究的有关软件编制、工作报告等在此期上发表。来稿要求观点明确、论据充足、论述简练、资料数据反映的情况务求核实准确。 相似文献
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古人对行星的称谓
古人很早就发现,在满天的繁星中,有5颗星非常与众不同：第一,它们不象其他星星那样“恒定”（保持着相对不动的位置）,而是在众星中游动;第二,它们都很亮,多数情况下亮度都超过或仅暗于天狼星,而且亮度不断发生变化。随着社会的进步,文明的发展,我们的先辈为这5颗特别的星星起了名字,大约在商、周时期,这5颗星分别被称作辰星、太白、荧惑、岁星、镇星（填星）,这就是今天肉眼可见的五星：水星、金星、火星、木星、土星。 相似文献