Energy-dependent transport problem with generalized boundary conditions

The slowing-down Boltzmann equation for generalized boundary conditions is considered and transformed to one-speed equation in Laplace space. Exact relations between energy reflection and transmission coefficients for a problem with diffuse reflecting boundary conditions and the albedos for the problem with isotropic boundary conditions are obtained. The Galerkin method is used to calculate the energy reflection coefficient for a finite slab for different thicknesses at different mass ratiosA, target to projectile mass, at different synthetic-scattering kernels. The results for partial heat fluxes for isotropic and anisotropic-scattering dispersive medium are given. The results obtained for isotropic boundary conditions are compared well with the exact results.     

Calculation of meteoroid impacts on moon and earth

Concise derivations are given for the expected flux of meteoroids to the surfaces of the earth and the moon. Contrary to other published results, we find an accretion rate which is lower for the near side of the moon than for the far side and which is lower for the moon than for the earth, for all earth-moon distances.     

Collective resonant phenomena on small bodies in the solar system

For both asteroids and meteor streams, and also for comets, resonances play a major role for their orbital evolutions but on different time scales. For asteroids both mean motion resonances and secular resonances not only structure the phase space of regular orbits but are mainly at the origin for the inherent chaos of planet crosser objects.For comets and their chaotic routes temporary trapping into orbital resonances is a well known phenomenon. In addition for slow diffusion through the Kuiper belt resonances are the only candidates for originating a slow chaos.Like for asteroids, resonances with Jupiter play a major role for the orbital evolution of meteor streams. Crossing of separatrix like zones appears to be crucial for the formation of arcs and for the dissolution of streams. In particular the orbital inclination of a meteor stream appears to be a critical parameter for arc formation. Numerical results obtained in an other context show that the competition between the Poynting-Robertson drag and the gravitational interaction of grains near the 2/1 resonance might be very important in the long run for the structure of meteor streams.     

原子钟时域频率稳定度分析中等效自由度的计算与分析

该文基于标准化自协方差函数的组合算法计算了阿仑方差、哈达玛方差的重叠和非重叠形式以及改进阿仑方差、时间方差的等效自由度,并用经验公式计算了总方法估计的等效自由度,在此基础上对各种方差估计不同噪声情况下的等效自由度进行了比较分析,得出如下结论,总方法估计的等效自由度大于相应非总方法估计的等效自由度,重叠和非重叠阿仑方差估计的等效自由度大于相应哈达玛方差估计的等效自由度;对非重叠估计而言,噪声的频率越低,其等效自由度越大;而相应的重叠估计和总方法估计与之相反,噪声的频率越高,其等效自由度越大,这也说明重叠估计和相应的总方法估计对高频噪声等效自由度的提高优于低频噪声.     

Prediction of satellite motions in the Earth's gravitational field with axial symmetry by the KS regularized theory

In this paper, economical and stable recurrence formulae for the Earth's zonal potential and its gradient for the KS regularized theory will be established for any numberN of the zonal harmonic coefficient. A general recursive computational algorithm based on these formulae is also established for the initial value problem of the KS theory for the prediction of artificial satellites in the Earth's gravitational field with axial symmetry. Applications of the algorithm for the problem of the final state prediction are illustrated by numerical examples of three test orbits each for two geopotential models corresponding toN=2 andN=36. A final state of any desired accuracy is obtained for each case study, a result which shows the flexibility of the algorithm.     

Particle escape probability for inhomogeneous medium

The particle escape probability from a non-multiplying slab containing an internal source is defined in terms of a functional relation for the scattering function for the diffuse reflection problem. The Padé approximation technique is used to obtain numerical results for particle escape probability for inhomogeneous medium. Numerical results for homogenous and inhomogeneous media are given.     

埃文斯目视日晕光度计测量原理研究

埃文斯目视日晕光度计（Evans Visual Sky Photometer,EVSP）是应用于日冕仪选址的重要仪器,从20世纪40年代一直使用至今,它为现代日晕光度计的定标提供了参考标准。通过使用云南天文台现存的一架EVSP研究了它的工作原理,并重点介绍了所利用的简易定标方法。给出了国际现有的多台EVSP日晕亮度定标曲线。由于EVSP内部光学元件反射率和透过率,以及中性渐变光楔的光学密度等存在未知的时间缓变特点,因此利用这种新定标手段可以高效经济地获得各自的定标曲线。     

On the mixing rules for astrophysical inhomogeneous grains

We present the computation of effective refractive coefficients for inhomogeneous two-component grains with three kinds of inclusions with   m _incl= 3.0 + 4.0i, 2.0 + 1.0i, 2.5 + 0.0001i  and a matrix with   m_m = 1.33 + 0.01i  for 11 volume fractions of inclusions from 0 to 50 per cent and wavelengths  λ= 0.5  , 1.0, 2.0 and 5.0 μm. The coefficients of extinction for these grains have been computed using a discrete dipole approximation. Computation of the extinction by the same method for grains composed of a matrix material with randomly embedded inclusions has been carried out for different volume fractions of inclusions. A comparison of extinction coefficients obtained for both models of grain material allows one to choose the best mixing rule for a mixture. In cases of inclusions with   m _incl= 2.0 + 1.0i  and 2.5 + 0.0001i the best fit for the whole wavelength range and volume fractions of inclusions from 0 to 50 per cent has been obtained for the Lichtenecker mixing rule. In the case of   m _incl= 3.0 + 4.0i  the fit for the whole wavelength range and volume fractions of inclusions from 0 to 50 per cent is not very significant but the best fit has been obtained for the Hanai rule. For volume fractions of inclusions from 0 to 15 per cent a very good fit has been obtained for the whole wavelength range for Rayleigh and Maxwell-Garnett mixing rules.     

On Alfvén's critical velocity for the interaction of a neutral gas with a moving magnetized plasma

A theory for the interaction of a neutral gas with a moving magnetized plasma is given. The Alfvén expression for the critical velocity is identified with that for the terminal velocity while another expression for the threshold velocity for interaction is given. The implications of these results to the Alfvén-Arrhenius model for the solar system are discussed.Paper dedicated to Professor Hannes Alfvén on the occasion of his 70th birthday, 30 May, 1978.     

Report of the IAU Working Group on Cartographic Coordinates and Rotational Elements: 2009

Every three years the IAU Working Group on Cartographic Coordinates and Rotational Elements revises tables giving the directions of the poles of rotation and the prime meridians of the planets, satellites, minor planets, and comets. This report takes into account the IAU Working Group for Planetary System Nomenclature (WGPSN) and the IAU Committee on Small Body Nomenclature (CSBN) definition of dwarf planets, introduces improved values for the pole and rotation rate of Mercury, returns the rotation rate of Jupiter to a previous value, introduces improved values for the rotation of five satellites of Saturn, and adds the equatorial radius of the Sun for comparison. It also adds or updates size and shape information for the Earth, Mars?? satellites Deimos and Phobos, the four Galilean satellites of Jupiter, and 22 satellites of Saturn. Pole, rotation, and size information has been added for the asteroids (21) Lutetia, (511) Davida, and (2867) ?teins. Pole and rotation information has been added for (2) Pallas and (21) Lutetia. Pole and rotation and mean radius information has been added for (1) Ceres. Pole information has been updated for (4) Vesta. The high precision realization for the pole and rotation rate of the Moon is updated. Alternative orientation models for Mars, Jupiter, and Saturn are noted. The Working Group also reaffirms that once an observable feature at a defined longitude is chosen, a longitude definition origin should not change except under unusual circumstances. It is also noted that alternative coordinate systems may exist for various (e.g. dynamical) purposes, but specific cartographic coordinate system information continues to be recommended for each body. The Working Group elaborates on its purpose, and also announces its plans to occasionally provide limited updates to its recommendations via its website, in order to address community needs for some updates more often than every 3 years. Brief recommendations are also made to the general planetary community regarding the need for controlled products, and improved or consensus rotation models for Mars, Jupiter, and Saturn.     

Survey and evaluation of eucrite bulk compositions

Abstract— The purpose of this survey is to establish reference bulk elemental abundances for the eucrites and thereby provide the basis to test core formation models as well as partial melting, fractional crystallization and magma ocean theories for the eucrite parent body. In order to evaluate bulk elemental abundances for the eucrites, 296 peer-reviewed articles, monographs, theses or books and 143 abstracts dating from 1938 to 1997 were surveyed. Of the 101 eucrites having at least one set of elemental abundance analyses reported in the literature, 20 were selected for in-depth examination. The selection criteria of our sample were based on the total number of analyses available for a given eucrite and the total number of elements for which data exist. The mean bulk elemental abundance, 1σ standard deviation, and the percent deviation were calculated for each element in a given eucrite. In order to evaluate the quality of the mean abundances, the elements were then grouped according to availability of data and percent deviations. Possible reasons for the different deviations in the different groups are briefly discussed. From the major element abundances, the normative (CIPW) composition, the molar compositions of pyroxene, olivine and plagioclase, and the bulk densities were calculated and compared to petrographic observations. The calculated norms for the noncumulates agree well with the observations while the norms for the cumulates do not. Possible reasons for this are discussed. Unfortunately, analyses of many elements are poorly represented in the literature and many bulk analyses suffer from unacceptable levels of uncertainty. Therefore, future work requires bulk elemental analyses for some of the more poorly characterized elements in eucrites, especially those of key elements used for planetary modeling.     

Galactic chaos driven by an oscillating massive particle

The effect of an oscillating massive particle on the motion of stars in a spherical Plummer gravitational system is examined for chaotic behaviour for ratios of satellite to parent galaxy masses ranging from .001 to .15. Thee-folding times for chaos are calculated for non-zero angular momentum orbits and discussed in relation to the time-scales for dynamical friction.     

Relative Equilibria for General Gravity Fields in the Sphere-Restricted Full 2-Body Problem

Equilibrium conditions for a mutually attracting general mass distribution and point mass are derived and their stability computed. The equilibrium conditions can be reduced to six equations in six unknowns, plus the existence of four integrals of motion consisting of the total angular momentum and energy of the system. The equilibrium conditions are further reduced to two independent equations, and their theoretical properties are studied. We derive three distinct conditions for a relative equilibrium which can be used to derive robust algorithms for solving these problems for non-symmetric gravity fields: a set of necessary conditions, a set of sufficient conditions, and a set of necessary and sufficient conditions. Each of these conditions is well suited for the computation of certain classes of equilibria. These equations are solved for non-symmetric gravity fields of interest, using a real asteroid shape model for the general gravity fields. Explicit conditions for the spectral and energetic stability of the resulting equilibria are also derived and computed for the shape of interest.     

Mapping monthly quantiles of ionospheric electron content and foF2

Monthly quantiles of ionization parameters are important information for system planning and to assess one aspect of ionospheric variability. For ionosonde parameters the data base is probably large enough to allow mapping of deciles. For electron content the situation is not so good: at least for Europe the data base only allows to construct maps for the upper and and the lower monthly quartiles.We present mapping procedures and maps for monthly quartiles of electron content and of foF2 based on experiences with mapping procedures for monthly medians. It turned out that for the lower quartiles it is necessary to to use more coefficients for the quartile maps than for the median maps.We discuss possibilities to gain decile information for electron content from foF2. For a few selected months and locations deciles can be gained from the Faraday effect on the signals of geostationary satellites. These selected cases are used to check on procedures to use foF2 experience to construct electron content deciles.     

Final touchdown phases and a guidance and control methodology for a soft Moon landing

This article continues our study of spacecraft guidance and control for a soft Moon landing (see our article “Main braking phase for a soft Moon landing as a form of trajectory correction”). Rationale is given for the objectives of the subsequent (final touchdown) phases. Analytical relations for the main parameters are obtained, and the impact of various disturbing factors is estimated. A methodology is proposed for calculating the main parameters for the whole braking sequence from the sighting altitude of the main braking phase termination to braking engine thrust and its throttle range.     

New set of geometrical and physical elements of the two variable stars SW lacertae and OO aquilae

Photoelectric observations of the two eclipsingvariables, were obtained in UBV standard system, for SWLac and, inVB standard system for OOAql.A new set of geometrical and physical elements for thesystems were obtained from both minima, through theirmagnitude variation during the observation time using themethod of: Fourier Analysis Techniques in-Frequency-domain for thelight curve changes. The two eclipsing variables are contact, the firstcontact angle was 48.1^° for SW Lac and 47.7^° for OO Aql.Absolute elements and effective temperatures of the twocomponents for both systems are derived.     

LBT: Its Instrumentation and Key Science Projects

B25 The site testing for the Thirty Meter Telescope and its potential role in developing the shortterm forecasting of observing conditions B34 LUCIFER: a NIR Spectrograph and Imager for the LBT B41 PEPSI: the Potsdam Echelle Polarimetric and Spectroscopic Instrument for the Large Binocular Telescope B44 LUCIFER: High Redshift Science Cases B49 Feedback in galaxy cores: a LBT Key Science Project proposal B52 SERPIL/LIINUS: a design study for a Near‐Infrared Interferometric Integral Field Spectrometer for the LBT B64 The Construction of the Large Binocular Telescope B73 Operating the LUCIFER Instrument B85 M92 – a crucial testbed for atomic diffusion and mixing in stars B142 The Large Binocular Camera at LBT B148 LUCIFER and its Exposure‐Time‐Calculator B196 The Multi‐Object Double Spectrograph and Nulling Interferometer for the Large Binocular Telescope B199 The Laser Guide Star Facility for the LBT B231 The PEPSI “deep spectrum” project B236 Zeeman‐Doppler imaging from Stokes IQUV line profiles B257 D3Dnet: getting ready for MUSE, a 2nd Generation Instrument for the VLT     

Inelastic cross section for antihelium on nuclei: an empirical formula for use in the experiments to search for cosmic antimatter

An empirical formula for the cross section for inelastic hadronic interaction of antihelium with nuclei for the projectile energy range from 0.3 GeV/n to 80 GeV/n and target atomic mass number A from 4 to 120 has been developed. It is based on the available experimental data of nucleon (antinucleon) — nucleus and helium — nucleus inelastic cross sections. Such a formula is needed by experiments designed to search for antihelium in cosmic rays. With this formula one can estimate the efficiency of antihelium detection and correct for antihelium attenuation in the atmosphere for the balloon-borne experiments. A byproduct of this work is an empirical formula for antiproton-nucleus inelastic cross.     

Dynamical and compositional assessment of near‐Earth object mission targets

Abstract— Using an H‐plot analysis, we identify 234 currently known near‐Earth objects that are accessible for rendezvous with a “best case” delta‐V of less than 7 km/s. We provide a preliminary compositional interpretation and assessment of these potential targets by summarizing the taxonomic properties for 44 objects. Results for one‐half (22) of this sample are based on new spectroscopic measurements presented here. Our approach provides an easy‐to‐update method for giving guidelines to both observers and mission analysts for focusing on objects for which actual mission opportunities are most likely to be found. Observing prospects are presented for categorizing the taxonomic properties of the most accessible targets that are not yet measured.     

Appulses and occultations of SAO stars by mercury: 1987–1995

Predictions are presented for 78 close approaches by Mercury to stars in the SAO catalog between 1 January 1987 and 31 December 1995. No easily observable occultations were found, but 7 occultations of stars with visual magnitudes of 7 or fainter were found. These events are presented for the use of observers searching for material in the vicinity of Mercury and for those who need close bright stars for the improvement of ground-based images of Mercury.