说明

中国科学院国家授时中心承担国家的授时任务,保持着我国高精度的原子时基准,负责目前由国家授时中心(NTSC)、上海天文台(SO)、北京天文台(BAO)、测量与地球物理研究所武昌时辰站(WTO)和北京无线电计量测试研究所(BIRM)共同组成的我国综合原子时TA(JATC)的归算工作,通过专用长、短波授时台发播我国的标准时间与标准频率信号,并通过本刊向用户提供广泛的授时业务信息。     

Winding sense of galaxies around the local supercluster

We present an analysis of the winding sense(S and Z-shapes) of 1 621 field galaxies that have radial velocity between 3 000 km s-1 and 5 000 km s-1.The preferred alignments of S-and Z-shaped galaxies are studied using chi-square,autocorrelation and Fourier series tests.We classify all the galaxies into 32 subsamples and notice a good agreement between the position angle(PA) distribution of the S-and Zshaped galaxies.The homogeneous distribution of the S-and Z-shaped galaxies is more noticeable for the late-...     

说明

中国科学院国家授时中心承担国家的授时任务,保持着我国高精度的原子时基准,负责目前由国家授时中心（wrsc）、匕海天文台（SO）、北京天文台（BAO）、测量与地球物理研究所武昌时辰站（WTO）和北京无线电计量测试研究所（BmM）共同组成的我国综合原子时TA（JATC）的归算工作,通过专用长、短波授时台发播我国的标准时间与标准频率信号,并通过本刊向用户提供广泛的授时业务信息。     

基于飞机观测资料的石家庄秋季对流层CH4垂直分布特征

为研究石家庄秋季对流层内CH₄垂直分布特征,2018年9月使用“空中国王350”飞机搭载Picarro温室气体在线观测仪和气象要素观测设备,对石家庄上空（600—5500 m）CH₄浓度进行探测。探测期间共飞行7架次,取得7条CH₄浓度廓线数据。结果表明: 石家庄上空近地面层（1000 m以下）CH₄平均浓度与同时间段区域背景站上甸子站CH₄浓度呈显著正相关（r=0.81,P < 0.03）。探测到的CH₄浓度最小值为1898×10^-9摩尔分数,最大值为2219×10^-9摩尔分数,平均浓度为1981×10^-9摩尔分数。观测得到的7条廓线均有较好的一致性,2000 m以上,浓度均随高度呈先增大后减小的趋势。利用后向轨迹模式（HYSPLIT）对探测时段内石家庄上空不同高度层主要气流传输路径进行统计分析表明,600 m高度输送路径较短,CH₄浓度受本地排放影响较大; 3000 m受输送作用影响较大,偏西和西南路径可能将较高CH₄浓度气团输送至石家庄上空; 5000 m气团传输对CH₄浓度影响较小,浓度相对较稳定,对传输路径的变化不敏感。     

Detection and Correction of AMSR-E Radio-Frequency Interference

Radio-frequency interference (RFI) affects greatly the quality of the data and retrieval products from space-borne microwave radiometry. Analysis of the Advanced Microwave Scanning Radiometer on the Earth Observing System (AMSR-E) Aqua satellite observations reveals very strong and widespread RFI contam- inations on the C- and X-band data. Fortunately, the strong and moderate RFI signals can be easily identified using an index on observed brightness temperature spectrum. It is the weak RFI that is diffi- cult to be separated from the nature surface emission. In this study, a new algorithm is proposed for RFI detection and correction. The simulated brightness temperature is used as a background signal (B) and a departure of the observation from the background (O-B) is utilized for detection of RFI. It is found that the O-B departure can result from either a natural event (e.g., precipitation or flooding) or an RFI signal. A separation between the nature event and RFI is further realized based on the scattering index (SI). A positive SI index and low brightness temperatures at high frequencies indicate precipitation. In the RFI correction, a relationship between AMSR-E measurements at 10.65 GHz and those at 18.7 or 6.925 GHz is first developed using the AMSR-E training data sets under RFI-free conditions. Contamination of AMSR-E measurements at 10.65 GHz is then predicted from the RFI-free measurements at 18.7 or 6.925 GHz using this relationship. It is shown that AMSR-E measurements with the RFI-correction algorithm have better agreement with simulations in a variety of surface conditions.     

国际地球参考框架(ITRF)的原点和无整体旋转

目前国际地球参考框架(ITRF)建立和维持中,参考架原点和其定向随时间演变的约束上,并没有遵循协议地球参考系(CTRS)的定义。ITRF的定义和实现不一致的这种特征,将对毫米级地球参考框架的构建产生重要的影响。分析和讨论了最新的国际地球参考框架(ITRF2005)的原点和定向随时间演变的问题,并提出了目前可能解决的办法。     

Kalman算法在原子时计算中的应用研究

为了寻求改进地方原子时算法的可能性,基于原子钟的离散动态模型,分析研究了Kalman滤波算法在地方原子时计算中的具体应用。采用中国科学院国家授时中心的18台铯原子钟数据,分别计算出基于ALGOS算法和经典Kalman算法的时间尺度。结果表明,两种时间尺度在性能方面极为相似,短期和长期频率稳定度相当。     

说明

<正>中国科学院国家授时中心承担国家的授时任务,保持着我国高精度的原子时基准,负责目前由国家授时中心(NTSC)、上海天文台(SO)、北京天文台(BAO)、测量与地球物理研究所武昌时辰站(WTO)和北京无线电计量测试研究所(BIRM)共同组成的我国综合原子时TA(JATC)的归算工作,通过专用长、短波授时台发播我国的标准时间与标准频率信号,并通过本刊向用户提供广泛的授时业务信息。     

Why are halo coronal mass ejections faster?

Halo coronal mass ejections (CMEs) have been to be significantly faster than normal CMEs, which is a long-standing puzzle. In order to solve the puzzle, we first investigate the observed properties of 31 limb CMEs that clearly display loopshaped frontal loops. The observational results show a strong tendency that slower CMEs are weaker in white-light intensity. Then, we perform a Monte Carlo simulation of 20000 artificial limb CMEs that have an average velocity of ～523km s -1. The Thomson scattering of thes...     

用于测量圆顶视宁度的微温脉动仪的研制

为评价云南天文台丽江2.4m望远镜的圆顶视宁度,研制了一种能测量温度、气压和微温脉动的仪器。在天文圆顶附近,望远镜前方光路上,放置几组微温传感器,可以测得圆顶附近影响天文观测的湍流强度的分布情况。介绍了这套仪器的基本原理,电路设计,程序设计,实验定标以及一个简单的测试。