A 20 cm2 CCD mosaic camera for a dark matter search part I : Mechanics,optics and cryogeny     

Arnaud  M.  Aubourg  E.  Bareyre  P.  Br';ehin  S.  Caridroit  R.  de Kat  J.  Dispau  G.  Djidi  K.  Gros  M.  Lachièze-Rey  M.  Laigneau  Y.  Laurent  B.  Lesquoy  E.  Lavocat  Ph.  Magneville  C.  Mazeau  B.  Milsztajn  A.  Moscoso  L.  Pasquaud  J.  Paul  B.  Perrin  P.  Petibon  J.  Piret  Y.  Queinnec  F.  Rich  J.  Spiro  M.  de Trogoff  J.  Vigroux  L.  Zylberajch  S.  Ansari  R.  Cavalier  F.  Moniez  M.  Beaulieu  J. P.  Ferlet  R.  Grison  Ph.  Vidal-Madjar  A.  Adrianzyk  G.  Berger  J. P.  Burnage  R.  Delclite  J. C.  Kohler  D.  Magnan  R.  Richaud  A.  Guibert  J.  Moreau  O.  Tajahmady  F.  Baranne  A.  Maurice  E.  Prévôt  L.  Gry  C. 《Experimental Astronomy》1994,4(3-4):265-278

A 20cm ² CCD mosaic camera has been especially built to search for dark galactic halo objects by the gravitational microlensing effect. The sensitive area is made of 16 edge-buttable CCDs developped by Thomson-CTS, with 23×23 µm ² pixels. The 35 kg camera housing and mechanical equipment is presented. The associated electronics and data acquisition system are described in a separate paper. The camera resides at the focal plane of a 40 cm, f/10, Ferson reflector. The instrument has been in operation since December 1991 at the La Silla Observatory (ESO).  相似文献   

黑洞吸积盘的演化及温度分布的热不稳定性     

汪定雄  杨兰田  陆烨 《中国天文和天体物理学报》1994,(4)

本文在Ｔｈｏｒｎｅ工作的基础上讨论了吸积盘中黑洞的有关参量的演化，以及由Ｓｃｈｗａｒｚｓｃｈｉｌｄ黑洞吸积盘向Ｋｅｒｒ黑洞吸积盘演化过程中对吸积盘辐射通量的影响，最后针对几个典型的辐射过程，分别讨论了黑洞吸积盘在牛顿框架中的温度分布方程与广义相对论的温度分布方程的热不稳定性，并给出此类问题的热不稳定性的判据。  相似文献   

A shipborne- type wave-height meter for oceangoing vessels, using microwave Doppler radar     

Yasuda  A. Kuwashima  S. Kanai  Y. 《Oceanic Engineering, IEEE Journal of》1985,10(2):138-143

A wave-height meter using a simple microwave Doppler radar,simeq10mW in power and 10.525 GHz in frequency, is proposed so that we can measure oceanic waves effectively while the ship is steaming. It was first applied to the measurement of the variation of water level generated in a wave tank, which suggested that it is adequately applicable to the measurement of oceanic waves. A field test was carried out off the cape of Nojimazaki by installing the Doppler radar 5 m above the sea level at the bow of the ship. The result agreed reasonably well with that measured simultaneously by the ultrasonic wave-height meter installed at the same position. Another test is running successfully on a larger ship with the wave-height meter installed at 9 m above the sea level. The significant wave height measured by the present meter is being compared with that observed visually by the navigation officers.  相似文献   

Analytic result for the properties of gravitational waves emitted by a large class of model sources     

H. Beltrami  W. Y. Chau 《Astrophysics and Space Science》1985,111(2):335-341

Expressions for the mass quadrupole moment tensor in the model for a wide variety of astrophysical objects are shown to be identical in form. This makes it possible to obtain analytical expressions for the gravitational radiation emitted by the sources, as well as the angular distribution, polarization dependence, and the wave forms of the radiation.  相似文献   

The Expansion of the Hamiltonian of the Planetary Problem into the Poisson Series in All Keplerian Elements (Theory)     

Kholshevnikov  K. V.  Greb  A. V.  Kuznetsov  E. D. 《Solar System Research》2001,35(3):243-248

The study of the evolution of planetary systems, primarily of the Solar System, is one of the basic problems of celestial mechanics. The stability of motion of giant planets on cosmogonic time scales was established by numerical and analytical methods, but the question about the evolution of orbits of terrestrial planets and arbitrary solar-type planetary systems remained open. This work initiates a series of papers allowing one to advance in solving the problem of the evolution of the solar-type planetary systems on cosmogonic time scales by using powerful analytical tools. In the first paper of this series, we choose the optimum reference system and obtain the Poisson series expansion of the Hamiltonian of the problem in all Keplerian elements. We propose to use the integral representation of the corresponding coefficients or the Poisson processor means instead of conventionally addressing any possible special functions. This approach extremely simplifies the algorithm. The next paper of this series deals with the calculation of the expansion coefficients.  相似文献   

Regolith Surface Reflectance: A New Attempt to Model     

Petrova  E. V.  Markiewicz  W. J.  Keller  H. U. 《Solar System Research》2001,35(4):278-290

The reflectance coefficient of the regolith layer of celestial bodies has been studied in relation to the physical properties of regolith particles (size, refractive index, and packing density) on the basis of an accurate numerical radiative-transfer algorithm for a semi-infinite flat layer. Using the geometric-optics approximation, we have found that a shape mixture of randomly oriented spheroids can successfully model the single-scattering phase function of independent soil grains. In order to take into account the effect of packing density in a regolith layer, the concept of the so-called static structure factor was used. The main effect of increasing packing density is to suppress the forward-scattering peak of the phase function and to increase the albedo of the reflecting surface. We also investigated the influence of fine dust on the reflected light. An addition of small particles not only increases the surface albedo, but also changes the brightness profile and enhances the backscattering. Although the problem of unique solution, which is inherent in the retrieval of the properties of a medium from the measurements of the intensity of light scattered by this media, cannot be removed in the proposed model, the procedure used here, in contrast to widely used approximations, allows us to fit observational data with a set of real characteristics of the regolith. Semiempirical approaches are able to fit the measurements well with a small number of free parameters, but they do not explicitly contain crucial physical characteristics of the regolith such as grain sizes or the refractive index. We compared the numerical solution of the radiative-transfer equation with the Hapke approximation, which is most often used by investigators. The errors introduced by the Hapke model are small only for near-isotropic scattering by isolated particles. However, independent regolith grains are known to scatter light mainly in the forward direction.  相似文献   

A unified model of dwarf nova outbursts based on the disk instability     

Y. Osaki  M. Hirose  S. Ichikawa 《Astrophysics and Space Science》1993,210(1-2):359-360

A unified model for outbursts of dwarf novae is proposed based on the disk instability model in cataclysmic variable stars. In this model, two different intrinsic instabilities (i.e., the thermal instability and the tidal instability) within accretion disks are considered in non-magnetic cataclysmic variable stars. It is suggested that all of three sub-classes of dwarf novae (i.e., U Gem-type, Z Cam-type and SU UMa-type dwarf novae) may be explained in terms of two model parameters of the orbital period of the binary and of the mass transfer rate within the framework of the disk instability model.  相似文献   

The Effect of Atmospheric Drag on Satellite Orbits During the Bastille Day Event     

Knowles  S.H.  Picone  J.M.  Thonnard  S.E.  Nicholas  A.C. 《Solar physics》2001,204(1-2):387-397

Geomagnetic storms driven by solar eruptions are known to have significant effects on the total density of the upper atmosphere in the altitude range 250–1000 km. This in turn causes a measurable effect on the orbits of resident space objects in this altitude range. We analyzed a sample of these orbits, both from sensor data and from orbital element sets, during the period surrounding the 14 July 2000 solar activity. We present information concerning the effects of this event on the orbits of resident space objects and how well accepted atmospheric models were able to represent it. As part of this analysis, we describe a technique for extracting atmospheric density information from orbital element sets. On daily time scales, the effect of geomagnetic activity appears to be more important than that of prompt radiation. However, the limitations in time and amplitude quantization of the accepted solar indices are evident. A limited comparison is also made with previous solar storm events.  相似文献   

AN INVESTIGATION OF FOREST MICROCLIMATE: THE PASOH FOREST RESERVE, NEGERI SEMBILAN, MALAYSIA     

Shaharuddin Ahmad  M.Phil.  Ph.D. 《Singapore journal of tropical geography》1991,11(1):68-75

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Challenging a Paradigm: Do We Need Active and Inactive Areas to Account for Near-Nuclear Jet Activity?     

Crifo  J.-F.  Rodionov  A. V.  Szegö  K.  Fulle  M. 《Earth, Moon, and Planets》2002,90(1-4):227-238

We briefly describe an advanced 3D gas dynamical model developed for the simulation of theenvironment of active cometary nuclei. The model canhandle realistic nucleus shapes and alternative physical models for the gas and dust production mechanism.The inner gas coma structure is computed by solving self-consistently(a) near to the surface the Boltzman Equation(b) outside of it, Euler or Navier-Stokes equations.The dust distribution is computed from multifluid ``zero-temperature' Euler equations,extrapolated with the help of a Keplerian fountain model.The evolution of the coma during the nucleus orbital and spin motion,is computed as a succession of quasi-steady solutions. Earlier versions of the model using simple,``paedagogic' nuclei have demonstrated that the surface orographyand the surface inhomogeneity contribute similarly to structuring the near-nucleusgas and dust coma,casting a shadow on the automatic attribution of such structures to ``active areas'.The model was recently applied to comet P/Halley, for whichthe nucleus shape is available. In the companion paper of this volume,we show that most near-nucleus dust structuresobserved during the 1986 Halley flybys are reproduced, assuming that the nucleus is strictly homogeneous. Here, we investigate the effect of shape perturbations and homogeneityperturbations. We show that the near nucleus gas coma structure is robust vis-a-vissuch effects. In particular, a random distribution of active and inactive areaswould not affect considerably this structure, suggesting that such areas,even if present, could not be easily identified on images of the coma.  相似文献