一种新型的双光束扫描卫星光通信捕获技术

提出了一种基于双光束扫描的卫星光通信捕获技术。使用两束信标光同时对目标卫星所在的不确定区进行扫描,目标卫星在探测到信标光后利用无线电信号向主动方卫星发送应答信号。通过对应答信号所携带信息的计算分析,最终确定目标卫星所在位置,实现捕获。数值仿真计算表明,该方法比传统方法扫描效率提高90%左右。     

基于双向反射分布函数的空间卫星紫外动态特性研究

根据目标所处的背景辐射环境,对空间卫星的紫外散射特性进行建模方法研究。依据目标表面材料属性与表面状况对目标表面进行区域分解与网格划分。基于辐射理论引入双向反射分布函数模型来描述目标表面网格单元的光散射特性,将目标各个表面所有网格单元散射分量叠加建立了目标紫外散射特性的数学模型。利用给定的目标几何结构尺寸和物性参数仿真获得了目标在轨动态光学特性。在某一观测角度下太阳帆板在探测光学系统入瞳产生的辐照度值与卫星本体接近,最大量级为10-11W/m2。仿真结果表明太阳帆板在目标特性分析时不可忽略。     

Image-processing techniques in precisely measuring positions of Saturn and its satellites

After overcoming the deficiencies of previous image-processing techniques, a novel technique based on the edge-detection of Saturnian ring is developed to precisely measure Saturn's position. Furthermore, the scattering light (i.e. halo light) of Saturn and its ring is removed effectively based on its center symmetry. Therefore, we have much more opportunities to accurately measure the positions of Mimas and Enceladus-- two satellites very close to the Saturn. Experimental tests with 127 frames of CCD images obtained on the 1-meter telescope at the Yunnan Observatory over three nights show that the geometric center of the Saturnian ring and its 4 satellites (Tethys, Dione, Rhea and Titan) have the same positional precision, and the standard error for a single observation is less than ±0.05 arcsec. It is believed that these new techniques would have important impetus to the positional measurement of both Saturn by using a CCD meridian instrument and its faint satellites by using a long focal length telescope.     

Structural Study of Methyl Acrylate in a Nematic Liquid Crystal by 1H NMR with 13C Satellites

The molecular structure and conformation of methyl acrylate have been determined by analyzing the ¹H NMR spectrum with ¹³C satellites of the molecules dissolved in the liquid crystal ZLI 1132. In the structural analysis, direct coupling constants have been corrected for molecular vibrations and converted to those in the r structure. The correlation between reorientational motion and internal rotation has been taken into account by using the mean external potential described in terms of bond interaction tensors. The potential for the internal rotation about the bond has been represented as V() = (V ₁/2) (1 – cos ) + (V ₂/2)(1 – cos 2), where is zero for the s-cis configuration, and the determined values of V ₁ and V ₂ are 2.7(1) and 8.4(13) kJ mol^–1, respectively. The relative abundance of the s-cis conformer, 76(1)%, agrees with a gas-phase value, 67(11)%, determined by electron diffraction within experimental errors.     

The impact of the new Earth gravity model EIGEN-CG03C on the measurement of the Lense-Thirring effect with some existing Earth satellites

The impact of the latest combined CHAMP/GRACE/terrestrial measurements Earth gravity model EIGEN-CG03C on the measurement of the Lense-Thirring effect with some linear combinations of the nodes of some of the existing Earth's artificial satellites is presented. The 1-sigma upper bound of the systematic error in the node-node LAGEOS-LAGEOS II combination is 3.9% (4% with EIGEN-GRACE02S, ∼ 6% with EIGEN-CG01C and ∼ 9% with GGM02S), while it is 1% for the node-only LAGEOS-LAGEOS II-Ajisai-Jason-1 combination (2% with EIGEN-GRACE02S, 1.6% with EIGEN-CG01C and 2.7% with GGM02S).     

Volatile Depletion in Planet-Forming Disks

Newly born stars are surrounded by gas and dust with a flattened axisymmetric distribution termed protoplanetary disk, in which planets are formed. Observations of these objects are necessary for understanding the formation and early evolution of stars and planets, and for revealing the composition of the raw material from which planets are made. Numerical models can extract important parameters from the observational data, including the gas and dust mass of the disk. These parameters are used as input for further modeling, e.g., to calculate the chemical composition of the disk. A consistent thermochemical model should be able to reproduce the abundances of different species in the disk. However, this good wish has been challenged for many disks: models over-predict the emission line intensity of some species; namely, they are depleted (with respect to expectations from canonical models). In this review we show how this disparity indicates that dust evolution has significant effects on gas chemistry, and may indicate the earliest stages of planet formation.     

准分子宽带泵浦碱金属激光器

基于国内外相关研究成果,对准分子宽带泵浦碱金属激光器(XPAL)的原理进行了阐述,对其优缺点进行了分析,针对半导体泵浦碱金属蒸气激光器(DPAL)发展中所面临的困难,分析了XPAL解决这些困难的潜力。最后综述了XPAL近年的发展,提出了下一步的发展方向。     

Compaction of icy/rocky porous mixtures at low temperatures (from 262K TO 77K) - preliminary results

Abstract

Rheology of icy/rocky porous mixtures relevant to material of icy satellites of giant planets was studied experimentally. The lower limit of temperature was that of liquid nitrogen and the pressure was up to 17.7 MPa. The compaction rate was studied and empirical formula was fitted. The dependence of formula parameters upon pressure, temperature and rock concentration was established.     

Quadrature discretization method in tethered satellite control

A pseudospectral method for solving the tethered satellite retrieval problem based on nonclassical orthogonal and weighted interpolating polynomials is presented. Traditional pseudospectral methods expand the state and control trajectories using global Lagrange interpolating polynomials based on a specific class of orthogonal polynomials from the Jacobi family, such as Legendre or Chebyshev polynomials, which are orthogonal with respect to a specific weight function over a fixed interval. Although these methods have many advantages, the location of the collocation points are more or less fixed. The method presented in this paper generalizes the existing methods and allows a much more flexible selection of grid points by the arbitrary selection of the orthogonal weight function and interval. The trajectory optimization problem is converted to set of algebraic equations by discretization of the necessary conditions using a nonclassical pseudospectral method.