西昆仑阿勒塔什地区ASTER影像岩性划分方法研究

以西昆仑造山带西段阿勒塔什地区为例,在缺少地表各岩石单元样品的情况下,对ASTER VNIR-SWIR波段反射率数据进行处理,提取岩性信息。首先对VNIR-SWIR多波段反射率数据进行最佳指数因子(IOIF)运算,得出最佳波段组合Band7-Band4-Band3,从其假彩色合成图像上只能识别少量岩性单元;为了减少高相关性波段之间的信息冗余度、并对波段信息进行集成,后对ASTERVNIR-SWIR波段反射率数据采用主成分变换并进行彩色合成,该图像能详细划分研究区多种岩性单元,如元古宙岩层、志留纪岩层、二长花岗岩岩体和英云闪长岩岩体,以及微观地质信息,如侵入岩热接触变质带、小型岩株和岩性界线。对比已有少量地质资料,认为提取结果可靠,为野外地质制图工作能提供超前信息。     

地球深部探测关键技术装备研发现状及趋势

地球深部探测技术装备为实施国家地壳探测工程战略计划、揭示地球深部奥秘提供技术保障,其发展水平将决定在辽阔的国土和海洋区域大面积、大深度获取数据和信息的能力。瞄准国际前沿装备技术,从国家高科技发展战略出发,针对复杂地质环境的探测能力和效率,自主研发深部探测仪器装备。基于研究现状和基础,从6个关键技术开展工作,分阶段落实探测工程战略计划,迅速提升整体技术水平。通过跨部门联合建设研发基地、汇集优秀人才、培训人员,引进、消化、吸收国外高端产品技术,加速完善自主创新、产学研用相结合的发展模式,迅速改变我国深探仪器装备长期依赖进口局面,在较短时期内完成从起步到成熟阶段的跨越式发展。     

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嫦娥二号伽玛射线谱仪

嫦娥二号卫星是我国继嫦娥一号卫星成功发射后的第2颗探月卫星,其上搭载的伽玛射线谱仪(Gamma-Ray Spectrometer,GRS)的主要科学目标是探测月表O、Si、Fe、Ti、U、Th、K、Mg、Al、Ca等主量元素.相比嫦娥一号伽玛射线谱仪,嫦娥二号的能量分辨率和探测效率都大大提高.描述了嫦娥二号伽玛射线谱仪的设计和性能测试结果以及在轨飞行的初步探测成果.     

Origin of the Speckles in Nanoengineered Tilted Liquid Mirrors

We report on progress in the development of the technology of nanonengineered liquid mirrors that use metal-coated viscous liquids. In a recent article, we found that viscous liquid mirrors tilted by 1° were marred by speckles that degraded their surfaces. We have now identified printtrough as the source of the speckles and offer solutions to the problem.     

An Optical,Dual-Beam,Automated Medium Resolution Spectropolarimeter for the Vainu Bappu Telescope

Fabrication of an optical dual-beam spectropolarimeter as an add-on facility to an existing astronomical spectrograph at the Vainu Bappu Telescope is described. The polarimetric optics consists of a superachromatic Pancharatnam design half-wave plate and a modified Glan-Taylor polarizing beam splitter. Instrumental response, calibration and characterization of the system are presented. Performance of the spectropolarimeter has been assessed based on the results of observations of polarized and unpolarized standard stars. The attainable accuracy of the instrument is found to be dependent on the S/N of the data. The present data set yields an accuracy of ±0.5% at 4000 Å and ±0.3% at 7500 Å, at a spectral resolution of 7.2 Å. Analysis of spectropolarimetric data is systematically covered for removal of instrumental errors. The spectropolarimetric reduction software (SPRS), extremely versatile, user friendly and compatible with the IRAF image processing package, was developed for reducing spectropolarimetric data. The empirical relation by Serkowski (IAU Symposium 52, Interstellar Dust and Related Topics, J. M. Greenberg and H. C. van de Hulst (eds.), Dordrecht, Reidel, 1975, p. 145) for wavelength dependence of polarization due to interstellar medium has been fitted to the data for the star HD 43384 (9 Gem). Our result shows a polarization larger by 0.49% from Hsu and Berger (ApJ 262, 1982, 732). We attribute this difference to the long term variation in P for this star.     

Diffraction losses in ground-based optical interferometers

We present a numerical analysis of free-space propagation of the beams inside a long-baseline optical/infrared interferometer. Unlike the models of beam propagation used in most previous studies, our analysis incorporates the effects of atmospheric seeing on the wavefronts entering the interferometer. We derive results for the changes in throughput, coherence loss and fringe-detection signal-to-noise ratio arising from diffraction along the propagation path. Our results for conditions of moderate seeing show that although the flux throughput decreases with propagation distance for a given beam diameter, the fringe contrast increases at the same time. In this case it becomes possible for diffraction to increase the signal-to-noise ratio of the fringe measurements. Previous studies have only considered an arrangement where all the apertures in the beam-propagation system have the same diameter. If the light at the end of the propagation path is collected with a fixed size aperture, we find that in many cases the signal-to-noise ratio for fringe detection is maximized when the initial beam diameter is approximately 30 per cent smaller than the final collector diameter. We discuss the implications of our results in the context of future interferometer designs.     

A digital signal pre-processor for pulsar search

A fast digital signal processor has been designed and built for survey and some observations of pulsars. The processor obtains spectral information over a bandwidth of 16 MHz (256 channels) every 25μsecs Wedescribethe design ofthisprocessor and present some test observations made with the Ooty Radio Telescope.