共查询到20条相似文献，搜索用时 94 毫秒
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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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2008年3月20-22日,东亚VLBI研讨会(East Asia VLBI Workshop)在中国科学院上海天文台召开.共76位代表注册参加了会议,他们分别来自澳大利亚(1人)、韩国(10人)、日本(19人)和中国(46人). 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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将不同波段的星表、特别是巡天项目产生的大型星表进行交叉证认,一直是进行多波段天文学研究,尤其是数据挖掘、统计分析研究的瓶颈.本文开发和实现了一个不依赖于特定数据库的海量星表融合系统(简称为XMaS_VO),用户能够方便地使用此系统的服务进行星表的上传及自动入库、交叉证认等工作.此外,XMaS_VO具备可移植性,如果用户需要进行很大数量的或者大型星表的交叉证认服务,可以自己建立数据库,方便地将此工具移植到自己的服务器上,自己使用或者开放服务给他人.随着该系统的进一步发展和应用.天文学家将可以轻松自如地获得他们需要的多波段融合数据,自由地选取参数和匹配的结果.从而可以更加有效地从事海量数据处理和分析工作. 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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一种扩大FAST视场的方法 总被引：1，自引：0，他引：1
所有的大口径射电望远镜都存在这样一个问题：在其分辨率和灵敏度提高的同时，视场变小．而且口径越大，视场越小．这成为大口径望远镜不可回避的矛盾．要解决这个矛盾，可以在望远镜的焦平面上放置Ⅳ个分立馈源．让它们同时工作，这样可以看作把视场扩大了Ⅳ倍．望远镜的工作效率提高Ⅳ倍．但是这样做的缺点是——视场不连续．且馈源数目Ⅳ受到望远镜焦比(F／D)的限制．采用致密焦面阵(dense focal plane array)就可以很好地解决这个问题．致密焦面阵的单元不是喇叭口天线，而是无方向性的Vivaldi天线(Vivaldi antenna)．要把Vivaldi阵列应用到望远镜上，需要对单个Vivaldi天线和Vivaldi阵列的电性能有清楚的认识，并能根据需要来设计照明方向图．还要知道大望远镜的焦面上电磁场的分布情况，借此判断能否应用Vivaldi阵列，以及给出Vivaldi单元的分路赋权网络．主要给出了FAST的焦面场的分布情况．并说明应用Vivaldi阵列的可能性． 相似文献
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Pavel Spurný 《Earth, Moon, and Planets》1995,68(1-3):529-537
Many Perseid meteors were photographed in the Czech part of the European Fireball Network during the activity of the new strong and sharp maximum on August 12, 1993. Basic data on many of them were evaluated and radiants, atmospheric trajectories and some orbital elements are presented here and compared with atmospheric and orbital data of regular Perseids, which were photographed outside the new activity in 1993 and preceding years. No substantial difference between these two groups of Perseid meteors was found. 相似文献
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Using the optical data of the 1993 international watch of NGC 5141, we made follow-up reverberation mapping analyses of its broad line region (BLR). We found the transfer function of the BLR for the 1993 data is entirely different from that for the 1988 international watch. We conclude that the structure of the BLR had changed in those 5 years and it is this change in structure that is responsible for the very different sizes of the BLR deduced from the two sets of data. 相似文献
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Srivastava Nandita Gonzalez Walter D. Gonzalez Alicia L.C. Masuda Satoshi 《Solar physics》1998,183(2):419-434
Intense geomagnetic storms with DST index -100 nT were recorded on 9 March and 11 March 1993 associated with solar activity on 6 March and 9-10 March, respectively. In this paper, we discuss the characteristic features of the solar origins of the two events that gave rise to coronal and interplanetary disturbances and as a consequence produced strong geomagnetic activity at the Earth. The source of the activity in one case is attributed to a major 3M7.0 flare that occurred on 6 March 1993 and in the other case, to two large filament disruptions on the disk during 9-10 March, 1993. Both these sources were found to be located near changing or varying low-latitude coronal holes. They were also located close to the heliospheric currents sheets. Distinct X-ray activity was observed for both the events as observed by the Yohkoh SXT telescope. The detailed evolution and a comparison of these events on the basis of Yohkoh soft X-ray observations are presented here. 相似文献
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The 61 cm Lowell telescope at Perth Observatory has been automated by the Perth Astronomy Research Group (PARG) for the detection, confirmation and follow-up studies of supernovae and other transient events. This search program complements similar searches operating in the Northern Hemisphere, such as the Berkeley Supernova Search. The first supernova found by our search program, SN 1993k, was discovered on March 28, 1993 (IAUC 5733). The discovery has been made with the telescope in fully automated mode, including automated image analysis. We are currently imaging some 80 galaxies per night. Photometric methods for the analysis of lightcurves are at present being implemented. 相似文献
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M.I. Wanas 《Astrophysics and Space Science》1997,252(1-2):237-248
A non-LTE study of the Type IIb supernova 1993J in the galaxy M81 taking into account nonthermal ionization and line blocking effects is carried out. Hydrodynamical models and theoretical spectra clearly show that nonthermal ionization and excitation dominate after the second maximum, at day 30, and play a decisive role in reproducing both the smooth tail of the light curve and the emergence of helium lines in the spectrum, similar to those observed. Based on our model of supernova 1993J, we predict that the light curves of Type Ib supernovae should be subject to nonthermal ionization and excitation at earlier times than even those for supernova 1993J. In our model, the outburst of supernova 1993J is interpreted as the explosion of a 4 M red supergiant, which underwent core collapse and left a neutron star in a binary system. The progenitor is supposed to have a helium core mass of 3 M, corresponding to a 13 M main-sequence star. Supernova 1993J adds evidence to the scenario that Type Ib supernovae originate from moderately massive stars on the main sequence that have lost their hydrogen envelopes in interacting binary systems. 相似文献
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L. Zaninetti 《Astrophysics and Space Science》2011,333(1):99-113
A classical and a relativistic law of motion for a supernova remnant (SNR) are deduced assuming an inverse power law behavior
for the density of the interstellar medium and applying the thin layer approximation. A third equation of motion is found
in the framework of relativistic hydrodynamics with pressure, applying momentum conservation. These new formulas are calibrated
against a decade of observations of SN 1993J. The existing knowledge of the diffusive processes of ultrarelativistic electrons
is reviewed in order to explain the behavior of the ‘U’ shaped profile of intensity versus distance from the center of SN 1993J. 相似文献
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Howard (1993) finds a relationship between the tilt angles of BMRs (Bipolar Magnetic Regions) and the separation between their leading and following polarities; the tilt angle increases with polarity separation. Here we present a more detailed analysis of this relationship and show that this effect constrains the strength of the magnetic field at the bottom of the convection zone to a value between 40 and 150 kG, which confirms the constraints put by D'Silva and Choudhuri (1993) based on Joy's law (the tilt-latitude relationship), through an entirely different approach.Operated by the Association of Universities for Research in Astronomy, Inc., under CooperativeOperated by the Association of Universities for Research in Astronomy, Inc., under Cooperative 相似文献
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通过把从光球辐射出来的连续谱能量分成大量的光子包，然后用MonteCarlo方法跟踪这些光子包从光球向超新星包层外运动的过程，这一方法能很好地解决超新星的光谱拟合中的谱线覆盖问题，由于同时编制了用于构造超新星包层中的密度结构和丰度分布的程序，以及大量的用于比较观测和理论拟合的绘图和支持程序，使我们的MonteCarlo光谱拟合软件包能够很好地运用于超新星的早期光谱研究。本文给出了SN1993J在1993年4月13日的观测光谱的运行实例。 相似文献
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L. Valenziano 《Experimental Astronomy》1995,6(1-2):83-96
A valuable seeing estimation at Baia Terra Nova, Antarctica is deduced from meterological data by means of a model. A sounding balloon launching campaign was conducted during the late spring 1993 and summer 1993–94. Using certain assumptions seeing is estimated in daytime and spring-summer conditions. The results obtained can be considered as worst case ones and are discussed as a first step to future programs for astronomy in Antarctica. 相似文献
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Translated from Astrofizika, Vol. 36, No. 1, p. 163, January–February, 1993. 相似文献