A Faraday rotation template for the Galactic sky

Using a set of compilations of measurements for extragalactic radio sources, we construct all-sky maps of the Faraday rotation produced by the Galactic magnetic field. In order to generate the maps, we treat the radio source positions as a kind of 'mask' and construct combinations of spherical harmonic modes that are orthogonal on the masked sky. As long as relatively small multipoles are used, the resulting maps are quite stable to changes in the selection criteria for the sources, and show clearly the structure of the local Galactic magnetic field. We also suggest the use of these maps as templates for cosmic microwave background (CMB) foreground analysis, illustrating the idea with a cross-correlation analysis between the Wilkinson Microwave Anisotropy Probe ( WMAP ) data and our maps. We find a significant cross-correlation, indicating the presence of a significant residual contamination.     

基于Poulos弹性理论的被动桩改进算法

传统的Poulos弹性理论仅适合于均质土中土体侧向位移时桩的性状分析,无法考虑土的层状特性。通过引入层状地基中作用一水平集中力的广义Mindlin解和地面作用有竖向荷载时的应力和位移通解,对Poulos方法进行了改进,使之扩展到多层土中,还用于研究堆载条件下的被动桩变形和受力响应。算例分析表明,改进弹性理论要比Poulos方法更为严密、合理,提高了计算精度,应用范围也更广。     

GPS卫星反射信号增强技术研究

本文根据GPS卫星反射信号在海洋参数测量、无源雷达目标探测以及大地测绘中的应用,从天线接收、信号处理运算和多路径信号抵消角度,详细地研究了GPS卫星反射信号增强技术,给出了相应天线和电路结构及信号处理方法,并进行了计算机仿真,结果表明所提出的技术能增强GPS卫星反射信号。     

Mechanisms controlling the temporal variation of the sea ice edge in the Southern Ocean

This paper examines the mechanism controlling the short time-scale variation of sea ice cover over the Southern Ocean. Sea ice concentration and ice velocity datasets derived from images of the Defense Meteorological Satellite Program (DMSP) Special Sensor Microwave Imager (SSM/I) are employed to reveal this mechanism. The contribution of both dynamic and thermodynamic processes to the change in ice edge location is examined by comparing the meridional velocity of ice edge displacement and sea ice drift. In the winter expansion phase, the thermodynamic process of new ice production off the ice edge plays an important role in daily advances of ice cover, whereas daily retreats are mostly due to southward ice drift. On the other hand, both advance and retreat of ice edges in the spring contraction phase are mostly caused by the dynamic process of the ice drift. Based on the above mechanism and the linear relation between the degree of ice production at the ice edge and northward wind speed, the seasonal advance of ice cover can be roughly reproduced using the meridional velocity of ice drift at the ice edge.     

Cross-Calibration and Long-Term Monitoring of the Microwave Radiometers of ERS, TOPEX, GFO, Jason, and Envisat

The radiometers on board the satellites ERS-1, TOPEX/Poseidon, ERS-2, GFO, Jason-1, and Envisat measure brightness temperatures at two or three different frequencies to determine the total columnal water vapor content and wet tropospheric path delay, a major correction to the altimeter range measurements. In order to asses the long-term stability of the path delay, the radiometers are calibrated against vicarious cold and hot references, against each other, and against several atmospheric models. Four of these radiometers exhibit significant drifts in at least one of the channels, resulting in yet unmodeled errors in path delay of up to 1 mm/year, thus limiting the accuracy at which global sea level rise can be inferred from the altimeter range measurements.     

Difference characteristics of sea surface temperature observed by GLI and AMSR aboard ADEOS-II

This study compares infrared and microwave measurements of sea surface temperature (SST) obtained by a single satellite. The simultaneous observation from the Global Imager (GLI: infrared) and the Advanced Microwave Scanning Radiometer (AMSR: microwave) aboard the Advanced Earth Observing Satellite-II (ADEOS-II) provided an opportunity for the intercomparison. The GLI-and AMSR-derived SSTs from April to October 2003 are analyzed with other ancillary data including surface wind speed and water vapor retrieved by AMSR and SeaWinds on ADEOS-II. We found no measurable bias (defined as GLI minus AMSR), while the standard deviation of difference is less than 1°C. In low water vapor conditions, the GLI SST has a positive bias less than 0.2°C, and in high water vapor conditions, it has a negative (positive) bias during the daytime (nighttime). The low spatial resolution of AMSR is another factor underlying the geographical distribution of the differences. The cloud detection problem in the GLI algorithm also affects the difference. The large differences in high-latitude region during the nighttime might be due to the GLI cloud-detection algorithm. AMSR SST has a negative bias during the daytime with low wind speed (less than 7 ms⁻¹), which might be related to the correction for surface wind effects in the AMSR SST algorithm.     

高灵敏度机载L波段微波辐射计探测海表盐度

海水盐度是研究大洋环流和全球气候变化的重要参数,L波段(1400-1427MHz)微波辐射计是进行海水盐度遥感的最有效工具.在该频段内,微波辐射亮度温度对海水盐度变化的灵敏度为0.5K/psu,而用于海洋研究的盐度分辨率为0.1-0.2psu,要求微波辐射计的灵敏度优于0.1K.高灵敏度机载L波段微波辐射计,应用数字增益波动自动补偿和温度补偿技术,保证了系统的稳定性,并采用高效的滤波技术有效地抑制了全球定位信号(GPS)对接收机的干扰,灵敏度达到0.08K.进行了多次航空和海上对比遥感试验,获得了分辨率优于0.2psu、误差精度0.42psu的测量结果.     

非均匀月壤介质的被动微波辐射传输模拟

基于非均匀月壤物理模型和辐射传输方程,模拟月壤介质中的微波辐射传输特性,探讨频率、月壤厚度等与月表亮温的关系。结果表明:在低频段,月壤微波辐射亮温的动态变化范围较大,可探测的月壤厚度大,3 GHz时的最大可探测月壤厚度达12.4 m;在高频段对应的可探测月壤厚度较小,特别是从50GHz往后的频率段内,最大可探测月壤厚度均小于2 m。不同频率的亮温-厚度变化曲线没有交叉点,且频率越高,所能探测的月壤厚度越小。根据模拟结果,建立了月壤厚度与亮温的查找表。基于查找表,利用单个波段的亮温数据即可得到月壤厚度信息。     

被动震源进行地震勘探的可行性研究

为研究冲击钻机、打桩机、打夯机以及筑路机等设备工作时产生的震源,对开展工程地震勘探时的利用价值,在东庞矿2093工作面治水钻孔冲击钻进过程中进行了该项实验工作。试验采用WF-1006遥测数字地震仪及CGS-40型加速度检波器,接收排列之间方位角间隔20。,接收道数24道,道距5m,采样率1ms,记录长度2s。最近检波器距钻孔7m。利用SCHRAMM钻机产生的强大振动为被动震源,进行了250m、257m、183m、263m等不同钻井深度,以及与此相对应不同方位角（250°、250°、230°275°）的地震波接收试验。通过分析其地震记录,判定引发东庞矿矿井突水的陷落柱中心位于治水钻孔西南方向。该结论与三维地震勘探确定的陷落柱位置一致,可见通过选择合理的接收方式及参数,被动震源也能够用于地震勘探。     

中国深空测控网建立方案的研究

概述了深空测控网的基本技术要求,总结了我国卫星测控网和国内现有射电观测设施的技术、组成和分布,分析和论述了将我国现有的测控设施建设成深空测控网的具体方案。