Pre-Impact Mid-IR and Optical Observations of Comet 9P/Tempel 1

Comet 9P/Tempel 1, the target of the Deep Impact mission, has been intensively observed for a long time period before the encounter. Pre-impact ground based monitoring of the comet was an important prerequisite for the success of the first space experiment in which a comet is treated by an artificial impact. It provided the background data needed to disentangle the features caused by the impact from variations caused by the natural activity of the comet. In this paper we present results from the ESO-monitoring of the comet, conducted in the thermal infrared and optical spectral ranges during several months before the Deep Impact encounter with the comet.     

应用于金属矿勘查中的地面地震层析成像技术

在金属矿地震勘探中,反射地震是一种最常用的一种方法技术,为更有效地探测与金属矿有关的局部不均匀体,我们利用了地面地震层析成像技术。这里结合模型实验和在金属矿勘查中的应用实例,论述了地面地震层析成像技术的有效性。     

Seismic Imaging from a TBM

Summary Seismic monitoring from the head of a tunnel-boring machine (TBM) enables improved assessment of the risks associated with the tunnel-boring process. The monitoring system provides a live image of ground conditions along the trajectory followed by the TBM and detects local heterogeneities such as boulders, foundations, and other obstacles that commonly pass undetected using local geotechnical techniques. From a seismic perspective, the underground setting of tunnelling projects places limitations on imaging capability. The principal limiting factor is the size of the area upon which transducers can be installed. This limitation requires adjustments to traditional seismic imaging techniques in which a large area is assumed to be available for attaching the transducers. Recently developed short imaging operators take this limitation into account and are used in the examples described herein. The unique conditions of tunnelling yield two advantages over traditional settings in terms of imaging: rotation of the cutter wheel and the lateral progression of the TBM. Rotation of the cutter wheel, upon which the transducers are installed, provides the opportunity to illuminate obstacles from different angles in different recordings. Spatial progression of the TBM enables improvement in the illumination of obstacles and the signal-to-noise ratio by combining recordings from different lateral positions. In this paper, these specific aspects of seismic imaging during tunnelling are discussed via models that represent different cases encountered in actual tunnelling projects. These case studies demonstrate the way in which image quality along the trajectory of the TBM is improved over that in traditional settings. In this way, the risks associated with the tunnelling process can be more accurately assured.     

Isotopic and Elemental Imaging of Geological Materials by Laser Ablation Inductively Coupled Plasma-Mass Spectrometry

Laser ablation ICP-MS represents a promising new development for the acquisition of elemental and isotopic images from a variety of different materials. Compared to existing methods for imaging, it offers relatively rapid throughput, very wide dynamic range, a relatively clean mass spectrum, utility at a variety of scales (from μm to cm) and multi-element/isotopic capability. Although developing rapidly in the biological sciences, the method has not yet seen widespread application to geological materials. This contribution documents some preliminary experiments aimed at understanding the fundamental aspects of elemental and isotopic image acquisition using laser ablation ICP-MS. In particular, we note that ablation cell designs must be optimised to promote rapid system response, in contrast to the signal-smoothing that is often preferred for simple spot analyses. Furthermore, experimental parameters must be carefully evaluated on a system-by-system basis to avoid the blurring effects of re-sampling phenomena. With careful attention to these details, and development of appropriate data processing software, laser ablation ICP-MS imaging has much to offer workers in the Earth and environmental sciences.     

3-D electromagnetic imaging of a Palaeozoic plate-tectonic boundary segment in SW Iberian Variscides (S Alentejo, Portugal)

In SW Iberian Variscides, the boundary between the South Portuguese Zone (SPZ) and the Ossa Morena Zone (OMZ) corresponds to a major tectonic suture that includes the Beja Acebuches Ophiolite Complex (BAOC) and the Pulo do Lobo Antiform Terrane (PLAT). Three sub-parallel and approximately equidistant MT profiles were performed, covering a critical area of this Palaeozoic plate-tectonic boundary in Portugal; the profiles, running roughly along an NE–SW direction, are sub-perpendicular to the main Variscan tectonic features. Results of the three-dimensional (3-D) modelling of MT data allow to generate, for the first time, a 3-D electromagnetic imaging of the OMZ–SPZ boundary, which reveals different conductive and resistive domains that display morphological variations in depth and are intersected by two major sub-vertical corridors; these corridors coincide roughly with the NE–SW, Messejana strike–slip fault zone and with the WNW–ESE, Ferreira–Ficalho thrust fault zone. The distribution of the shallow resistive domains is consistent with the lithological and structural features observed and mapped, integrating the expected electrical features produced by igneous intrusions and metamorphic sequences of variable nature and age. The development in depth of these resistive domains suggests that: (1) a significant vertical displacement along an early tectonic structure, subsequently re-taken by the Messejana fault-zone in Late-Variscan times, has to be considered to explain differences in deepness of the base of the Precambrian–Cambrian metamorphic pile; (2) hidden, syn- to late-collision igneous bodies intrude the meta-sedimentary sequences of PLAT; (3) the roots of BAOC are inferred from 12 km depth onwards, forming a moderate resistive band located between two middle-crust conductive layers extended to the north (in OMZ) and to the south (in SPZ). These conductive layers overlap the Iberian Reflective Body (evidenced by the available seismic reflection data) and are interpreted as part of an important middle-crust décollement developed immediately above or coinciding with the top of a graphite-bearing granulitic basement.     

二维圆周综合孔径阵列优化及其毫米波成像特性研究

运用模拟退火算法对由20-30根天线组成的二维圆周综合孔径阵列进行优化排列,得到优化排布结果。在此基础上依据综合孔径成像的基本原理,分析了毫米波的成像算法,在u-v域运用了栅格化处理（Gridding方法）和线性插值方法。运用该成像算法对已优化排布的阵列进行了仿真,并进一步讨论了天线数目、插值方法等因素对成像特性的影响。     

Starspot distributions on XY UMa during 1997–2000 from eclipse mapping

We present narrow-band red light curves and surface maps of the short-period RS CVn binary system XY UMa, obtained between 1997 January and 2000 March. The light-curve morphology of this system is known to vary on time-scales of a few days. We have used eclipse-mapping techniques to map the distribution of cool starspots on the surface of the primary star. The resulting maps show the continued evolution of spot features on time-scales of a few days to a week. By comparison with the images of Collier Cameron & Hilditch, we also find evidence for longer term trends, including a decline to an activity minimum during 1997 and a rise in activity during 1998–2000. We also find marginal evidence from the O–C ephemeris curves for a periodicity and a peak corresponding to the time of activity minimum.     

CFH12K: Optimizing 12 MIT/LL CCID20 CCDs for a Direct Imaging Application

CFH12K is a 12 k by 8 k wide field imaging camera for the CFHT prime focus. The mosaic consists of twelve MIT Lincoln laboratories 2 k by 4 k thinned backside illuminated CCID20 devices. The devices’ operating parameters have been optimized to ensure the best data quality for use in broad and narrow band filter imaging mode. Adaptation to the CFHT prime focus environment included modifications to reduce the scattered light seen by the CFH12K. Science data taken by the camera has proven the success of CFHT’s new capability for 42 by 28 arcmin² imaging with high resolution subarcsecond seeing. This revised version was published online in July 2006 with corrections to the Cover Date.     

In-flight Performance of the Advanced Camera for Surveys CCDs

The Advanced Camera for Surveys (ACS), installed in the Hubble Space telescope in March 2002, will significantly extend HST's deep, survey imaging capabilities. ACS has met, or exceeded, all of its key performance specifications. In this paper we briefly review the in-flight performance of the instrument's CCD detectors and preview early ACS science observations. This revised version was published online in July 2006 with corrections to the Cover Date.     

深部矿产勘查的地震学方法：问题与前景——铜陵矿集区的应用实例

深部资源是未来资源勘查的重要方向,地震技术在深部资源勘查中具有不可替代的优势。为试验该方法在探测深部“层控”矿床和浅表容矿构造方面的有效性,进一步完善金属矿地震勘查技术,在铜陵矿集区进行了反射地震和首波地震层析方法试验。结果显示,反射地震技术可以精确确定研究区的主要容矿层位石炭系黄龙组与泥盆系五通组接触面的空间分布,并能清晰反映地表5km深度内的大尺度结构、构造;首波地震层析技术可以揭示浅表岩体形态。试验结果表明,该技术对在中国东部“第二富集带”寻找深部“层控”矿床具有潜在的应用价值,预示着广阔的应用前景。