共查询到20条相似文献，搜索用时 62 毫秒
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Yong Zhang Xiang-Qun Cui National Astronomical Observatories / Nanjing Institute of Astronomical Optics & Technology Chinese Academy of Sciences Nanjing Graduate School of the Chinese Academy of Sciences Beijing 《中国天文和天体物理学报》2005,5(3):302-314
Large Sky Area Multi-Object Fibre Spectroscopic Telescope (L AMOST) is one of the major on-going national large scientific projects in China. Active optics is a key technology for the LAMOST with which the thin-mirror active optics and segmented-mirror active optics are tied in. A pre-calibration method considering all active forces and displacements specially for LAMOST has been developed in early 2004. We give a detailed mathematical derivation and calculation including numerical simulation and computer program realization of the pre-calibration method of LAMOST open-loop control for the third-order as-pherical aberration. We have also carried out calculations on the application of the pre-calibration method and the parameters of actuator design in LAMOST active optics in observation mode, including estimations of the actuator ranges, the interval of active optics correction and the ranges and trends of load changes on all the actuators during LAMOST tracking a given star. 相似文献
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李凤云 韩智洁 刘明旭 淳于波 徐亚军 陈余 李双虎 闫秋浩 包铁威 郭王伟 李义成 李新南 王晋峰 田杰 乔撩云 陈亮 吕金虎 陈超 刘承 张勇 侯永辉 王跃飞 葛群 左恒 姜方华 李烨平 陆启帅 胡守伟 王佑 李爱华 倪季君 张超 倪小康 许静 李浩 李晓飞 张昊彤 白仲瑞 胡天柱 王丹 崔向群 赵永恒 李国平 《天文学报》2022,63(1):12-126
对大口径光学/红外天文望远镜而言,为保障其稳定高效运行,镜面镀膜是重要的维护环节之一.镀膜质量的好坏直接影响镜面光学反射率的高低,也严重影响到天文望远镜的成像质量、观测效率.国家重大科技基础设施—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,又名郭守敬望远镜)自2009年6月通过国家竣工验收并逐步投入巡天观测,目前已进入第2个5 yr巡天计划阶段,取得近两千万的光谱产出和大批高显示度的科学成果. LAMOST共拥有24块施密特改正镜子镜和37块球面主镜子镜,为了确保在野外恶劣观测环境下镜面反射率维持在较高水平,每年要对大批子镜进行镀膜.主要介绍了镀膜需求、镀膜设备,并基于大量实验和多年的完善探索出一套可行的镀膜工艺流程,确保了LAMOST子镜极高的镀膜质量.镀膜后子镜平均反射率高达90%以上,满足了LAMOST光谱巡天的镜面反射率要求. 相似文献
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Ding-Qiang Su Xiang-Qun Cui National Astronomical Observatories/NIAOT Chinese Academy of Sciences Nanjing Department of Astronomy Nanjing University Nanjing 《中国天文和天体物理学报》2004,4(1):1-9
Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) is one of the major national projects under construction in China. Active optics is one of the most important technologies for new large telescopes. It is used for correcting telescope errors generated by gravitational and thermal changes. Here, however, we use this technology to realize the configuration of LAMOST, -a task that cannot be done in the traditional way. A comprehensive and intensive research on the active optics used in LAMOST is also reported, including an open-loop control method and an auxiliary closed-loop control method. Another important development is in our pre-calibration method of open-loop control, which is with some new features: simultaneous calculation of the forces and displacements of force actuators and displacement actuators; the profile of mirror can be arbitrary; the mirror surface shape is not expressed by a fitting polynomial, but is derived from the mirror surface shape formula which is highly accurat 相似文献
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介绍国家“九五”重大科学工程项目“大天区面积多目标光纤光谱天文望远镜(LAMOST)”中基于QNX(Quick UNIX)操作系统的实时分布式数据库的研究情况。此项研制已通过2002年7月2日由LAMOST工程指挥部组织的北京、南京和合肥三地专家的评审，并得到好评。该数据库功能强、工具丰富、操作方便，在类UNIX操作系统下实现了Windows的界面风格，可以满足LAMOST控制系统数据在线(或离线)处理、存储、程序生成表格和图形等需要，也可推广应用到其它相关领域。 相似文献
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光纤是LAMOST子系统焦面仪器的四个主要组成部分之一。它是LAMOST望远镜收焦的星光从焦面到光谱仪的传输介质。尽可能高的传输效率是我们追求的目标。LAMOST的光纤采用芯径320μm的STU光纤。我们在实验室对其性能作了初步测试。结果令人满意。 相似文献
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基于优先策略的动态选星算法 总被引：1，自引：0，他引：1
论述了LAMOST巡天观测战略系统(SSS)中观测策略的实现方法选星算法问题．以国外SDSS望远镜为例介绍了静态选星算法，分析了其不足之处，并结合LAMOST望远镜的特点，提出了一种新的选星算法-“动态选星”算法．动态选星算法基于优先策略原理，可以在满足覆盖完备性的基础上，优化观测效率，并能方便地兼顾观测条件的约束．给出了算法的原理和框架描述，并针对算法进行了模拟计算，证明了算法的有效性．另外需要指出的是动态选星算法不仅适用于LAMOST，它可以普遍地应用于多目标光纤望远镜的巡天选星． 相似文献
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近代天文圆顶发展概况 总被引：2，自引：0，他引：2
综述了国内外天文圆顶的各种设计方案，比较了各种方案的性能，并介绍了为改善圆顶性能，降低造价进行的相关研究，以及为下一代巨型地面望远镜圆顶进行的预研究．结合目前正在研制的大天区多目标光纤光谱望远镜——LAMOST，简述了我国LAMOST望远镜圆顶的设计方案及其相关研究的概况。 相似文献
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《天文和天体物理学研究(英文版)》2015,(11)
HD 49798(a hydrogen depleted subdwarf O6 star) with its massive white dwarf(WD) companion has been suggested to be a progenitor candidate of a type Ia supernova(SN Ia). However, it is still uncertain whether the companion of HD 49798 is a carbon-oxygen(CO) WD or an oxygen-neon(ONe) WD. A CO WD will explode as an SN Ia when its mass grows and approaches the Chandrasekhar limit, but the outcome of an accreting ONe WD is likely to be a neutron star. We generated a series of Monte Carlo calculations that incorperate binary population synthesis to simulate the formation of ONe WD + He star systems. We found that there is almost no orbital period as large as HD 49798 with its WD companion in these ONe WD + He star systems based on our simulations, which means that the companion of HD 49798 might not be an ONe WD. We suggest that the companion of HD 49798 is most likely a CO WD, which can be expected to increase its mass to the Chandrasekhar limit by accreting He-rich material from HD 49798. Thus, HD 49798 and its companion may produce an SN Ia as a result of its future evolution. 相似文献
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André Deprit 《Celestial Mechanics and Dynamical Astronomy》1979,20(4):319-323
A recursive procedure is established to evaluate series in themth derivatives of Legendre polynomials. It is applied to evaluate a gravitational potential, the components of its gradient and the elements of its Hessian. 相似文献
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We investigate the HD 182255, a star earlier suspected to be helium-weak. We show it to be a SiHe-w-type CP object. Our study
revealed four regions with anomalous elemental abundances on the stellar surface near the equator of rotation. Its magnetic
field could not be measured, apparently due to the unfavorable orientation of the star. The star is seen almost (rotation)
pole on, the inclination of its rotation axis is i = 12°. The magnitude of HD 182255 varies as a result of its rotation owing to the nonuniform distribution of chemical elements
on its surface, which leads to the variable blanketing effect. The helium and silicon abundances increase with depth, i.e.,
the stratification typical of CP stars is observed. The star undergoes nonradial pulsations and nonstationary variations of
the structure of its upper atmosphere. 相似文献
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给出了一种倾角函数及其导数的定积分计算方法,表达式十分简单,其计算精度:倾角函数可达10-15,导数可达10-13,可与Gooding方法相媲美.该方法的稳定性和适用倾角范围均较好,可供倾角函数的最高阶数Lmax≤50时使用. 相似文献
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This study presents an automated system for cataloging impact craters using the MOLA 128 pixels/degree digital elevation model of Mars. Craters are detected by a two-step algorithm that first identifies round and symmetric topographic depressions as crater candidates and then selects craters using a machine-learning technique. The system is robust with respect to surface types; craters are identified with similar accuracy from all different types of martian surfaces without adjusting input parameters. By using a large training set in its final selection step, the system produces virtually no false detections. Finally, the system provides a seamless integration of crater detection with its characterization. Of particular interest is the ability of our algorithm to calculate crater depths. The system is described and its application is demonstrated on eight large sites representing all major types of martian surfaces. An evaluation of its performance and prospects for its utilization for global surveys are given by means of detailed comparison of obtained results to the manually-derived Catalog of Large Martian Impact Craters. We use the results from the test sites to construct local depth-diameter relationships based on a large number of craters. In general, obtained relationships are in agreement with what was inferred on the basis of manual measurements. However, we have found that, in Terra Cimmeria, the depth/diameter ratio has an abrupt decrease at ∼38°S regardless of crater size. If shallowing of craters is attributed to presence of sub-surface ice, a sudden change in its spatial distribution is suggested by our findings. 相似文献
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A radio source with a spectral index of −2.2 between 0.08 and 1.425 GHz has been observed at the Very Large Array (VLA) at 1.425 GHz with resolution ∼ 3 arcsec. The projected linear length of the source is 56 kpc with an average projected distance of 42 kpc from the centroid of the rich southern cluster Abell 4038, assuming the source is in the cluster. The physical parameters of the source include a high minimum-energy field ( B me ) of 38 μG, which is unusual for a source of low surface brightness and relaxed appearance, but is explained by its unusually steep spectrum. Although its radio morphology has some characteristics of a narrow-angle-tail source (NAT), the absence of an identified host galaxy ( m R ≥ 23.0) makes it unlikely that the source is a working radio galaxy. The relic is probably the remains of an FR II radio galaxy that was once energized by a particular bright cluster elliptical now 18 kpc to its east. The density of the intracluster gas has been sufficient to confine the source and preserve its morphology, permitting the source to age and its spectrum to steepen through synchrotron and inverse Compton energy losses. 相似文献
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The planet Mars has many Earth like characteristics, but its evolution is different. An important future step in Mars’ geophysics is to deploy a network of stations at the surface of Mars inorder to study a wide range of properties of this planet, going from its deep interior structure to its atmosphere. Each ground station (small landers) will contain the same scientific instruments/experiments. The collected data will improve our knowledge of the Martian interior, surface and atmosphere, as well as its evolution. An important part of these objectives can only be achieved by a network of surface stations, as a network gives unique possibilities for performing studies of global scale phenomena and studies requiring simultaneous measurements from several sites. 相似文献
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Abstract— Fountain Hills is a metal‐rich chondrite with mineral and whole chondrite oxygen isotope compositions that suggest it is a CB chondrite. However, its petrologic characteristics suggest that it has been modified by shock and recrystallization to a greater degree than other CB chondrites. It differs texturally from the CB chondrites in that its metal is interstitial to the silicate and does not occur as discrete clasts as in the other CB chondrites. Portions of Fountain Hills appear to be recrystallized and it contains large (mm‐size) olivine rimmed by pyroxene. A characteristic of the CB chondrites is the presence of small sulfide blebs in large metal clasts and anomalously heavy (15N‐enriched) nitrogen often associated with metal surrounding the sulfide blebs, but Fountain Hills lacks sulfide and its nitrogen is relatively light. The differences between Fountain Hills and the other CB chondrites can be attributed to a secondary process, most likely impact‐melting and recrystallization, that overprinted its primary features and it is inferred that Fountain Hills is an impact‐modified CB chondrite. 相似文献
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Burrows A Guillot T Hubbard WB Marley MS Saumon D Lunine JI Sudarsky D 《The Astrophysical journal》2000,534(1):L97-L100
The recent discovery that the close-in extrasolar giant planet HD 209458b transits its star has provided a first-of-its-kind measurement of the planet's radius and mass. In addition, there is a provocative detection of the light reflected off of the giant planet tau Bootis b. Including the effects of stellar irradiation, we estimate the general behavior of radius/age trajectories for such planets and interpret the large measured radii of HD 209458b and tau Boo b in that context. We find that HD 209458b must be a hydrogen-rich gas giant. Furthermore, the large radius of a close-in gas giant is not due to the thermal expansion of its atmosphere but to the high residual entropy that remains throughout its bulk by dint of its early proximity to a luminous primary. The large stellar flux does not inflate the planet but retards its otherwise inexorable contraction from a more extended configuration at birth. This implies either that such a planet was formed near its current orbital distance or that it migrated in from larger distances (>/=0.5 AU), no later than a few times 107 yr of birth. 相似文献
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K. P. Singh G. C. Stewart N. J. Westergaard S. Bhattacharayya S. Chandra V. R. Chitnis G. C. Dewangan A. T. Kothare I. M. Mirza K. Mukerjee V. Navalkar H. Shah A. F. Abbey A. P. Beardmore S. Kotak N. Kamble S. Vishwakarama D. P. Pathare V. M. Risbud J. P. Koyande T. Stevenson C. Bicknell T. Crawford G. Hansford G. Peters J. Sykes P. Agarwal M. Sebastian A. Rajarajan G. Nagesh S. Narendra M. Ramesh R. Rai K. H. Navalgund K. S. Sarma R. Pandiyan K. Subbarao T. Gupta N. Thakkar A. K. Singh A. Bajpai 《Journal of Astrophysics and Astronomy》2017,38(2):29
The Soft X-ray focusing Telescope (SXT), India’s first X-ray telescope based on the principle of grazing incidence, was launched aboard the AstroSat and made operational on October 26, 2015. X-rays in the energy band of 0.3–8.0 keV are focussed on to a cooled charge coupled device thus providing medium resolution X-ray spectroscopy of cosmic X-ray sources of various types. It is the most sensitive X-ray instrument aboard the AstroSat. In its first year of operation, SXT has been used to observe objects ranging from active stars, compact binaries, supernova remnants, active galactic nuclei and clusters of galaxies in order to study its performance and quantify its characteriztics. Here, we present an overview of its design, mechanical hardware, electronics, data modes, observational constraints, pipeline processing and its in-orbit performance based on preliminary results from its characterization during the performance verification phase. 相似文献