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1.
Raynor L. Duncombe Paul D. Hemenway Arthur L. Whipple 《Celestial Mechanics and Dynamical Astronomy》1984,34(1-4):19-36
A 15 year project to establish a dynamical reference system utilizing ground-based and Space Telescope observations of 34 minor planets is being undertaken. The orbits of these minor planets will be knit into a common system through the use of crossing point observations. The system of orbits thus established can be used to measure long arcs in the sky (similar to the function of a transit circle) and can be used to detect individual star errors as well as residual periodic effects in the fundamental reference system. The minor planet dynamical reference system will also provide an independent method to establish the zero point and the solid-body rotation of the HIPPARCOS reference system. 相似文献
2.
The aim of the present paper will be to utilize the results obtained in the preceding papers of this series for the development of practical procedures for obtaining the elements of any eclipsing system from the observed photometric data by their analysis in the frequency-domain, for any type of eclipses, any proximity of the two components, and any degree of the law of limbdarkening of the eclipsed star.In Section 2, which follows a brief introduction to the subject, procedures will be developed which should permit us to perform such an analysis — by hand or automatic machine computation — for the case of mutual eclipses in binary systems the components of which can be regarded as spheres; and whose apparent discs are characterized by an arbitrary radially symmetrical distribution of surface brightness. In Section 3 we shall generalize these procedures to systems consisting of arbitrarily distorted stars.Paper dedicated to Professor Hannes Alfvén on the occasion of his 70th birthday, 30 May, 1978. 相似文献
3.
P. K. Seidelmann 《Celestial Mechanics and Dynamical Astronomy》1985,37(3):199-207
The present fundamental reference system is defined by the FK5 Fundamental Reference Catalog and the associated IAU Resolutions of 1976 through 1982. The past is defined to be what preceded the present fundamental reference system and future is defined to be what ever will come after it. The resulting characteristics of the different fundamental reference systems are considered from the aspects of the observational data, the computational methods, and the underlying theories. Having developed an understanding of these operational fundamental reference systems, the desired properties of the ideal fundamental reference system are presented. Finally, some questions concerning the future fundamental reference system are presented. 相似文献
4.
Ian A. Bonnell Kester W. Smith Melvyn B. Davies Keith Horne 《Monthly notices of the Royal Astronomical Society》2001,322(4):859-865
We investigate how the formation and evolution of extrasolar planetary systems can be affected by stellar encounters that occur in the crowded conditions of a stellar cluster. Using plausible estimates of cluster evolution, we show how planet formation may be suppressed in globular clusters while planets wider than ≳0.1 au that do form in such environments can be ejected from their stellar system. Less crowded systems such as open clusters have a much reduced effect on any planetary system. Planet formation is unaffected in open clusters and only the wider planetary systems will be disrupted during the cluster's lifetime. The potential for free-floating planets in these environments is also discussed. 相似文献
5.
Anna P. Kartashova 《Earth, Moon, and Planets》2012,108(3-4):165-173
We present a method for calculations of equatorial coordinates of any point in the single frame of the wide-field TV systems. This method can be applying for the different television systems [wide-field cameras, all-sky cameras, the cameras with the hybrid TV-system (the system with coupled of the Image Intensifier) et al.]. In that system the calculations of distortions are difficult. Therefore, we devised this method which helps decrease errors (due to distortion and the electro-optical system).The method can be used for measuring of equatorial coordinates of meteor tracks under difficult conditions during the observations such as partial cloudiness, small number of stars and large distortions of the coordinate grid in the frame. These restrictions cannot be overcome by other methods. In the case of the small number of stars the present method using of the reference stars received on a series of frames during the observation period. The accuracy of the method has been estimated to be 4′–8′ (for cameras with fov 50°?×?40° at the CCD 720?×?576 pixels) for maximum number of reference points in the frame. The method used 3 reference points for calculation of the equatorial coordinates of the object. One can use this method if the camera was re-oriented as well. We use this method for our wide field of view cameras. 相似文献
6.
IERS1996规范在参考系方面的改进 总被引：2，自引：0，他引：2
对ＩＥＲＳ１９９６规范中有关参考系方面作了简单而系统的介绍，重点叙述了与ＩＥＲＳ１９９２标准相比ＩＥＲＳ１９９６规范在参考系方面的主要改进：天球参考架中的基本源从５７颗增加到２３６颗；动力学参考架采用ＪＰＬ ＤＥ４０３／ＬＥ４０３历表代替ＤＥ２００／ＬＥ２００历表；采用ＮＵＶＥＬ ＮＮＲ－１Ａ板块运动模型代替ＮＵＶＥＬ ＮＮＲ－１模型；变更了９个基本常数值；给出了天极坐标的观测和理论间差的经验模型 相似文献
7.
It is suggested that the development of the SKA will drastically change the face of radio astronomy in the 21st Century. A
FAST-style SKA would admit observations of low contrast features, and would be the best design for studying the `dark ages'
of the Universe (x≫ 1) where sub-arcmin total power instruments can usefully be employed. To date there have been no proposals for post-SKA,
billion square-metra instruments; we speculate that mobile communication systems can be used. In the very distant future,
SKA multi-beam systems could be used to collect signals reflected by Solar system bodies such as the asteroid belt.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
8.
We propose a cooperative observational project of using the photo-electric astrolabe Mark I of Shaanxi Observatory in Irkutsk. As the instrument will be equipped with a Z = 45° angle prism, it will have no blind zone when used at latitude (φ = 52°. Important contribution can be expected to the establishing of fundamental reference system and the maintenance of the Hipparcos Catalogue system. 相似文献
9.
P. K. Seidelmann G. H. Kaplan K. J. Johnston C. M. Wade 《Celestial Mechanics and Dynamical Astronomy》1984,34(1-4):39-48
The weak thermal emission from the largest minor planets can be detected and measured at all points around their orbits at microwave frequencies using the Very Large Array (VLA). Position determinations of astrometric quality have been obtained, and flux measurements have provided size estimates. When enough precise positional observations have been accumulated, the orbits of the minor planets and the Earth can be determined. This will allow the equinox to be located within the radio reference frame, providing a truly fundamental coordinate system for radio source positions. It will also provide a means of relating the optical and radio (quasar) coordinate systems.The National Radio Astronomy Observatory is operated by Associated Universities, Incorporated, under contract with the National Science Foundation. 相似文献
10.
Celestial coordinate reference systems in curved space-time 总被引：1，自引：1，他引：0
S. M. Kopejkin 《Celestial Mechanics and Dynamical Astronomy》1988,44(1-2):87-115
11.
Using alternative independent variables in lieu of time has important advantages when propagating the partial derivatives of the trajectory. This paper focuses on spacecraft relative motion, but the concepts presented here can be extended to any problem involving the variational equations of orbital motion. A usual approach for modeling the relative dynamics is to evaluate how the reference orbit changes when modifying the initial conditions slightly. But when the time is a mere dependent variable, changes in the initial conditions will result in changes in time as well: a time delay between the reference and the neighbor solution will appear. The theory of asynchronous relative motion shows how the time delay can be corrected to recover the physical sense of the solution and, more importantly, how this correction can be used to improve significantly the accuracy of the linear solutions to relative motion found in the literature. As an example, an improved version of the Clohessy-Wiltshire (CW) solution is presented explicitly. The correcting terms are extremely compact, and the solution proves more accurate than the second and even third order CW equations for long propagations. The application to the elliptic case is also discussed. The theory is not restricted to Keplerian orbits, as it holds under any perturbation. To prove this statement, two examples of realistic trajectories are presented: a pair of spacecraft orbiting the Earth and perturbed by a realistic force model; and two probes describing a quasi-periodic orbit in the Jupiter-Europa system subject to third-body perturbations. The numerical examples show that the new theory yields reductions in the propagation error of several orders of magnitude, both in position and velocity, when compared to the linear approach. 相似文献
12.
R. R. White A. Allan S. Barthelmy J. Bloom M. Graham F. V. Hessman S. Marka A. Rots K. Scholberg R. Seaman C. Stoughton W. T. Vestrand R. Williams P. R. Wozniak 《Astronomische Nachrichten》2006,327(8):775-778
Networks are becoming a key element in most current and all future, telescope and observatory projects. The ability to easily and efficiently pass observation data, alert data and instrumentation requests between distributed systems could enable science as never before. However, any effective large scale or meta‐network of astronomical resources will require a common communication format or development resources will have to be continuously dedicated to creating interpreters. The necessary elements of any astronomy communication can be easily identified, efficiently described and rigidly formatted so that both robotic and human operations can use the same data. In this paper we will explore the current state of notification, what notification requirements are essential to create a successful standard and present a standard now under development by the International Virtual Observatory Alliance (IVOA), called the VOEvent. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
13.
George Gatewood Lee Breakiron Ronald Goebel Steven Kipp Jane Russell John Stein 《Icarus》1980,41(2):205-231
Extensive testing suggests that astrometric techniques can be employed to detect and study virtually any planetary system that may exist within 40 light years (12.5 parsec) of the Sun. Following the conclusion of Paper I [G. Gatewood, Icarus27 (1976), 1–12], the astrometric group at the Allegheny Observatory began an intensive survey of 20 nearby stars to detect the nonlinear variations in their motion that planetary systems would induce. Several tests conducted to further our understanding of the limitations of this survey indicated that the photographic detector itself is responsible for the majority of the random error. A new photoelectric detector has been designed and a simplified prototype of it successfully tested. The new detector is expected to be able to utilize virtually all of the astrometric information transmitted through the Earth's atmosphere. This is sufficient to determine relative positions to within an accuracy of approximately 1 milliarcsec/hr. Such precisions exceed the design capabilities of the best existing astrometric telescopes, thus a feasibility study has been conducted for the design of an improved instrument. The study concludes that a new ground-based telescope and the new detector combined should be able to study stars as faint as the 17th magnitude with an annual accuracy of a few tenths of a milliarcsecond. However, to obtain the ultimate accuracy possible from current technology, we must place an astrometric system above the Earth's atmosphere. A space-borne instrument utilizing the new detector would in theory have sufficient accuracy to detect any Earth-like planet orbiting any of the several hundred stars nearest the Sun. 相似文献
14.
在国际无线电科联于１９９３年９月在日本京都召开的第２４届大会上，射电在文专门委员会作出了成立大射电望远镜工作组的决议，以推动和促进跨世纪的新一代射电望远镜工程的研究和准备，这是一项广泛国际合作的巨大科学计划，ＮＧＲＴ的主要性能将比现有的，以及计划建造的最先进的射电望远镜还优一到两个数量级。本文拟介绍该计划的历史渊源和技术梗概，希望有助于我国天文界积极参与该项目的国际合作。 相似文献
15.
Cheongho Han 《Monthly notices of the Royal Astronomical Society》2002,335(1):189-194
If a source star is gravitationally microlensed by a multiple lens system, the resulting light curve can have significant deviations from the standard form of a single lens event. The chance of producing significant deviations becomes important when the separations between the component lenses are equivalent to the combined angular Einstein ring radius of the system. For multiple lens systems composed of more than two lenses, however, this condition is difficult to meet because the orbits of such systems are unstable. Even if events are caused by a multiple lens system with stable orbits where a pair of lenses are closely located and the other component (a third body) has a wide separation from the pair, identifying the lens multiplicity photometrically will be difficult because the event will be identified by either a binary lens event caused by the close pair of lenses or a single lens event caused by the third body. In this paper, we show that if a seemingly binary lens event is followed up astrometrically using future high-precision interferometers, the existence of an additional third body can be identified via a repeating event. We show that the signatures of third bodies can be unambiguously identified from the characteristic distortions they make in the centroid shift trajectories. We also show that owing to the long-range astrometric effect of third bodies, the detection efficiency will be considerable even for third bodies with large separations from their close lens pairs. 相似文献
16.
Zdeněk Kopal 《Astrophysics and Space Science》1980,70(2):329-362
The aim of the present paper will be to develop a theory of the radial-velocity changes of the components of close binary systems, with special attention to phenomena arising from finite dimensions of such components and their mutual distortion as well as irradiation. It is particularly stressed that the deformability of fluid stars and gas motions in their atmospheres can give rise to systematic differences between the observed radial velocities of such stars and those of their mass centres.In Section 2 (which follows a brief statement of the problem outlined in Section 1) we shall introduce the coordinate systems subsequently employed to treat various aspects of our problem: Section 3 will be concerned with an extraction of information from the radial-velocity component of absolute motions of the mass-centres of such stars; and in Section 4 we shall generalize the classical work by an investigation of radial velocities at any point of the apparent disks of distorted components, and their relation to the motion of their centres of mass. Section 5 will contain an evaluation of the effects of distortion, on radial velocity, averaged over the entire visible disk of the respective star at different phases; and in Section 6 we shall extend the same treatment to stars undergoing eclipses.An investigation of the effects, on the observed radial velocities, of atmospheric streaming caused by mutual irradiation of the two stars is being postponed for a subsequent communication. 相似文献
17.
平方公里阵列(Square Kilometre Array,SKA)项目是建设全球最大射电望远镜的国际合作项目,其灵敏度和测量速度将比当前所有的射电望远镜都要高出一个数量级.连续谱巡天是SKA的主要观测模式之一,基于连续谱成像建立巡天区域的标准星图,将能为后续天文科学研究奠定重要基础.银河系与河外星系全天默奇森宽场阵列拓展巡天(GaLactic and Extragalactic All-sky Murchison Widefield Array survey eXtended,GLEAM-X)是2018—2020年利用SKA先导望远镜默奇森宽场阵列(Murchison Wide-field Array,MWA)二期拓展阵列开展的新的射电连续谱巡天项目,观测期间积累了大量的低频巡天观测数据.海量观测数据的自动化、大批量处理是SKA望远镜项目所面临的的最大挑战和难题之一,基于分布式执行框架的成像管线优化经验将有助于解决海量数据处理问题.详细介绍了GLEAM-X成像管线并对其进行整合和改进,在中国SKA区域中心原型机(China SKA Regional Centre Prototype,... 相似文献
18.
Guenther Eichhorn Alberto Accomazzi Carolyn S. Grant Michael J. Kurtz Stephen S. Murray 《Astrophysics and Space Science》2002,282(1):299-340
The Astrophysics Data System (ADS) provides access to the astronomical literature through the World Wide Web. It is a NASA
funded project and access to all the ADS services is free to everybody world-wide. The ADS Abstract Service allows the searching
of four databases with abstracts in Astronomy, Instrumentation, Physics/Geophysics, and the LANL Preprints with a total of
over 2.2 million references. The system also provides access to reference and citation information, links to on-line data,
electronic journal articles, and other on-line information. The ADS Article Service contains the full articles for most of
the astronomical literature back to volume 1. It contains the scanned pages of all the major journals (Astrophysical Journal,
Astronomical Journal, Astronomy & Astrophysics, Monthly Notices of the Royal Astronomical Society, and Solar Physics), as
well as most smaller journals back to volume 1.The ADS can be accessed through any web browser without signup or login. Alternatively
an email interface is available that allows our users to execute queries via email and to retrieve scanned articles via email.
This might be interesting for users on slow or unreliable links, since the email system will retry sending information automatically
until the transfer is complete. There are now 9 mirror sites of the ADS available in different parts of the world to improve
access. The ADS is available at: http://ads.harvard.edu
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
19.
Multi-conjugate adaptive optics(MCAO),consisting of several deformable mirrors(DMs),can significantly increase the adaptive optics(AO)correction field of view.Current MCAO can be realized by either star-oriented or layer-oriented approaches.For solar AO,ground-layer adaptive optics(GLAO)can be viewed as an extreme case of layer-oriented MCAO in which the DM is conjugated to the ground,while solar tomography adaptive optics(TAO)that we proposed recently can be viewed as star-oriented MCAO with only one DM.Solar GLAO and TAO use the same hardware as conventional solar AO,and therefore it will be important to see which method can deliver better performance.In this article,we compare the performance of solar GLAO and TAO by using end-to-end numerical simulation software.Numerical simulations of TAO and GLAO with different numbers of guide stars are conducted.Our results show that TAO and GLAO produce the same performance if the DM is conjugated to the ground,but TAO can only generate better performance when the DM is conjugated to the best height.This result has important application in existing one-DM solar AO systems. 相似文献
20.
G. J. Murray J. R. Allington-Smith 《Monthly notices of the Royal Astronomical Society》2009,399(1):209-218
The fields of view of Extremely Large Telescopes will contain vast numbers of spatial sampling elements (spaxels) as their adaptive optics systems approach the diffraction limit over wide fields. Since this will exceed the detection capabilities of any realistic instrument, the field must be dilutely sampled to extract spectroscopic data from selected regions of interest. The scientific return will be maximized if the sampling pattern provides an adaptable combination of separated independent spaxels and larger contiguous subfields, seamlessly combining integral-field and multiple-object spectroscopy. We illustrate the utility of this diverse-field spectroscopy (DFS) to cosmological studies of galaxy assembly. We show how to implement DFS with an instrument concept: the Celestial Selector. This integrates highly multiplexed monolithic fibre systems and switching networks of the type currently available in the telecommunications industry. It avoids bulky moving parts, whose limitations were noted in Paper I. In Paper III, we will investigate the optimization of such systems by varying the input–output mapping. 相似文献