IERS数据动态提取与更新系统的设计与实现

在高精度的位置计算中需要获取计算时刻所在日期的闰秒,以及UT1-UTC等关键数据,但长期以来这一类数据的维护均是手工进行,出错率高.针对新一代中国太阳射电日像仪观测与数据处理过程中的位置计算需要,实现了一个自动提取国际地球自转服务（IERS）参数的数据更新自维护子系统.系统可以根据需要自动运行、自动下载并分拆IERS网站数据,采用正则表达式从文本中自动获取所需要的实测值与预报值,自动在本地构建一个2004年12月31日以来的IERS数据库,并根据每周所获得的数据维护整个IERS的数据,将最新的实测值与预报值存入数据文件,实现了数据的滚动更新.系统彻底解决了手工维护数据的问题,为中国太阳射电日像仪的自动数据处理流水线打下了较好的基础.同时,本文提出的方法是一种通用的方法,可以方便地集成应用到国内其它天文位置计算领域.     

1981-2012年辽宁省春播期土壤相对湿度月尺度数据重建

辽宁省现有测站春播期土壤相对湿度数据存在不连续性及长时间序列缺失问题。以海城站为例,分析现有土壤相对湿度（0-20 cm）与气象因子及临近站点土壤相对湿度的相关关系,构建海城春播期土壤相对湿度统计回归模型,模拟缺测时段春播期土壤相对湿度。进而以此方法重建辽宁省20个观测站1981-2012年春播期土壤相对湿度月尺度数据。结果表明：海城土壤相对湿度与降水量和秋季封冻雨关联较大,相关系数分别超过0.60和0.30,与同期临近站点本溪站土壤相对湿度相关性也超过0.40,依据该3要素构建的4月和5月土壤相湿度统计回归模型复相关系数R2分别达0.79和0.77,模拟结果与实测资料平均相对误差为2.6 %,模拟效果较好;对辽宁省其他数据缺失站点构建的回归模型复相关系数均高于0.50,模型拟合精度优于85 %,拟合值和实测值平均相对误差基本控制在15 %以内,较好完成辽宁省20个测站1981-2012年春播期土壤相对湿度月尺度数据重建。     

三维可视化填图在晴隆锑矿外围勘查中的应用

三维可视化技术在辅助传统地质方法工作的同时,将复杂地质体形态、地质构造情况以三维的形式表现出来,呈现较丰富的的视觉效果。首次把三维可视化技术应用于贵州晴隆锑矿田找矿,有较好效果。     

浅谈如何编好对外援助项目的工程概算

准确的工程概算和资料搜集对.外项目的顺利实施起着非常重要的作用,分析了编制.外工程概算的内容及方法,提出了做好编制工程概算应注意的问题。     

Top layers charaterization of the Martian surface: Permittivity estimation based on geomorphology analysis

Mars Express spacecraft inserted successfully Martian orbit at the end of 2003. On board this probe, a radar instrument called MARSIS (for Mars Advanced Radar for Surface and Ionosphere Sounding) is looking for water inside the first kilometers of Martian crust. To support MARSIS planning and data inversion, Laboratoire de Planétologie de Grenoble developed a MARSIS signal simulator.We show in this paper that MARSIS can also characterize some surface features, in addition to subsurface water and ionosphere sounding. We study a Martian surface region of special interest: Nilokeras Mensae, inside Acidalia Planitia. We discuss the previous geological studies of this region, and show the geomorphologies analyze of this surface area could lead to a simple terrain model. Then, we present a possible data inversion scheme and applying the MARSIS simulator, we test a first radar data inversion.Finally, we will show that complete dielectric characteristics of surface top layers can be retrieved, at least as often Mars Express flies over some layered terrain (at wavelength scale).     

Photometric calibration of the LASCO-C2 coronagraph for Solar System objects

We present a photometric calibration of the SOHO/LASCO-C2 coronagraph appropriate to Solar System objects based on the extensive analysis of all stars down to magnitude V=8 which transited its field-of-view during the past nine years of operation (1996-2004). An automatic procedure was developed to analyze some 143,000 images, and to detect, locate and measure those stars. Aperture photometry was performed using three different aperture sizes and the zero points of the photometric transformations between the LASCO-C2 magnitudes for its three filters (orange, blue and red) and the standard V magnitudes were determined after introducing a correction for the color of the stars. The calibration coefficients for the surface photometry of extended sources were then derived from the zero points. An analysis of their temporal evolution indicates a slight decrease of the sensitivity of LASCO-C2 at a rate of ∼0.7% per year.     

Gamma–hadron separation methods for the VERITAS array of four imaging atmospheric Cherenkov telescopes

Ground-based arrays of imaging atmospheric Cherenkov telescopes have emerged as the most sensitive γ-ray detectors in the energy range of about 100 GeV and above. The strengths of these arrays are a very large effective collection area on the order of 10⁵ m², combined with excellent single photon angular and energy resolutions. The sensitivity of such detectors is limited by statistical fluctuations in the number of Cosmic-ray initiated air showers that resemble γ-ray air showers in many ways. In this paper, we study the performance of simple event reconstruction methods when applied to simulated data of the Very Energetic Radiation Imaging Telescope Array System (VERITAS) experiment. We review methods for reconstructing the arrival direction and the energy of the primary photons, and examine means to improve on their performance. For a software threshold energy of 300 GeV (100 GeV), the methods achieve point source angular and energy resolutions of σ_63% = 0.1° (0.2°) and σ_68% = 15% (22%), respectively. The main emphasis of the paper is the discussion of γ–hadron separation methods for the VERITAS experiment. We find that the information from several methods can be combined based on a likelihood ratio approach and the resulting algorithm achieves a γ–hadron suppression with a quality factor that is substantially higher than that achieved with the standard methods used so far.     

A fast method for finding bound systems in numerical simulations: Results from the formation of asteroid binaries

We present a new code (companion) that identifies bound systems of particles in O(NlogN) time. Simple binaries consisting of pairs of mutually bound particles and complex hierarchies consisting of collections of mutually bound particles are identifiable with this code. In comparison, brute force binary search methods scale as O(N²) while full hierarchy searches can be as expensive as O(N³), making analysis highly inefficient for multiple data sets with N?¹⁰³. A simple test case is provided to illustrate the method. Timing tests demonstrating O(NlogN) scaling with the new code on real data are presented. We apply our method to data from asteroid satellite simulations [Durda et al., 2004. Icarus 167, 382-396; Erratum: Icarus 170, 242; reprinted article: Icarus 170, 243-257] and note interesting multi-particle configurations. The code is available at http://www.astro.umd.edu/zoe/companion/ and is distributed under the terms and conditions of the GNU Public License.     

Synthetic high-resolution near-IR spectra of the Sun for planetary data reductions made from ATMOS/Spacelab-3 and Atlas-3 data

We have constructed synthetic solar spectra for the 2302-4800 cm⁻¹ (2.08-4.34 μm) range, a spectral range where planetary objects mainly emit reflected sunlight, using ATMOS (Atmospheric Trace Molecule Spectroscopy)/Spacelab-3 and Atlas-3 spectra, of which resolution is 0.01 cm⁻¹. We adopted Voigt line profiles for the modeling of line shapes based on an atlas of line identifications compiled by Geller [Geller, M., 1992. Key to Identification of Solar Features. A High-Resolution Atlas of the Infrared Spectrum of the Sun and the Earth Atmosphere from Space. NASA Reference Publ. 1224, vol. III. NASA, Washington, DC, pp. 1-22], who derived solar line positions and intensities from contaminated high-resolution solar spectra obtained by ATMOS/Spacelab-3. Because the ATMOS spectra in these wavelength ranges are compromised by absorption lines of molecules existing in Earth's high-altitude atmosphere and in the compartment of the spacecraft, the direct use of these high-resolution solar spectra has been inconvenient for the data reductions of planetary spectra. We compared the synthetic solar spectra with the ATMOS spectra, and obtained satisfactory fits for the majority of the solar lines with the exception of abnormal lines, which do not fit with Voigt line profiles. From the model fits, we were able to determine Voigt line parameters for the majority of solar lines; and we made a list of the abnormal lines. We also constructed telluric-line-free solar spectra by manually eliminating telluric lines from the ATMOS spectra and filling the gaps with adjacent continua. These synthetic solar spectra will be useful to eliminate solar continua from spectra of planetary objects to extract their own intrinsic spectral features.