多层等效源曲面磁异常转换方法

在磁异常数据处理中,利用等效源技术重构磁异常场具有较好的稳定性和较高的计算精度,因而被广泛应用.传统方法是采用设置在近地表的单层等效源拟合实测磁异常数据,尽管拟合精度很高,但向上延拓之后往往会出现较大的拟合误差,即可能存在磁异常信号的"泄漏",尤其在原始数据中存在背景场时更容易出现此种误差.本文提出一种多层等效源技术方案,应用分布于不同深度范围内的等效源模拟实测数据,减少了等效源参数设置的盲目性.理论模型试验表明,采用多层等效源方法重构的磁异常及其梯度与分量,较单层等效源方法具有更高精度,可以吸收更完整的实测磁异常信息.论文详细地讨论了如何优化多层等效源设置、等效源参数选择以及计算方法,通过二维和三维理论模型试验,验证了在复杂条件下多层等效源方法的可行性和适应性,并且将该方法应用于广西某地的实测磁异常数据转换之中,取得了较好的应用效果.     

中国电离层TEC同化现报系统

数据同化是在基于物理机制的背景模型上,融合时空不规则分布的观测数据的一种现报方法.同化能够有效弥补数据的时空局限和模型的精度偏差,使二者相互匹配从而获得更加合理可信的模拟效果.本研究利用电离层数据同化方法,针对中国及周边区域（15°N-55°N,70°E-140°E）构建了电离层总电子含量（TEC）同化现报系统.系统使用国际参考电离层（IRI）作为背景场,利用中国科学院空间环境监测网和国际GNSS服务组织（IGS）的部分地基GNSS台站数据作为观测值,并采用三维变分与Gauss-Markov卡尔曼滤波相结合的算法进行背景场和观测值的数据同化,生成覆盖中国及周边区域的电离层TEC和GPS单频接收机延迟误差的格点化准实时现报地图,并在中国科学院空间环境预报中心（http：//sepc.ac.cn/TEC_chn.php）网上发布,每15 min进行更新.该系统是我国基于同化算法的电离层现报系统之一,已用于中国及周边区域的电离层环境实时监测,可为卫星导航、雷达成像、短波通信等科学研究和工程应用提供相对及时、准确、有效的电离层TEC和误差修正信息.     

数据采集器自动检测与断电重启的实现

针对太原基准地震台加速度观测中出现的数据采集器死机现象,使用Visual Studio 2015开发环境,对网络远程控制设备进行二次开发,编写自动处理软件,实现了对加速度数据采集器执行自动检测、自动断电复位和开启数据流的操作,为其他观测台站解决类似的问题提供技术参考。     

射电天线指向改正模型中轴系误差的完全表达式

为了提高射电天线的目标跟踪精度,采用直接法推导了射电天线轴系误差对指向的影响,并给出轴系误差指向改正模型的完全表达式,明确了指向改正模型中各轴系参数的定义,传统分项以及球谐函数所推导的轴系误差项为该模型的简化形式.基于此,评估得出基本参数改正模型中,因忽略轴系误差高次谐项而引起的指向精度损失可能达到1′′量级,具体需结合轴系误差大小而定;同时明确了基本参数改正模型(如22项指向模型)中与轴系误差有关的部分高次谐项系数的物理意义.为高精度轴系误差指向改正模型的建立提供了理论依据.     

亮红外星系NGC 1614中多谱线示踪的致密分子气体

利用高空间分辨率的¹²CO(1-0)、¹³CO(1-0)、¹²CO(3-2)、¹²CO(6-5)、HCN(3-2)、\lk HCN(4-3)、 HCO⁺(3-2)和HCO⁺(4-3)分子谱线的ALMA (Atacama Large Millimeter/ submillimeter Array)归档数据, 来研究近邻亮红外星系NGC 1614的分子气体性质, 尤其是致密分子气体的性质. 在高分辨率分子气体谱线的积分强度图中, 在星系中心区域($<$ 1kpc)可以看到环状结构, 分子气体主要分布于星系中心区域, 核区分子气体含量较少. ¹²CO(1-0)显示出向南部、 北部以及东南部的延展结构, 高阶的CO ($J \ge$ 3, J为转振能级量子数)分子谱线和致密分子HCN、HCO⁺谱线显示, 较致密的分子气体主要集中于星系中心区域. HCN(4-3)/¹²CO(1-0)和HCN⁺(4-3)/¹²CO(1-0)积分强度比值图显示, 致密分子气体主要集中于中心区域的环状结构上. HCN/HCO⁺强度比值的分布变化表明星暴环的不同区域可能具有不同的激发条件. HCN/HCO⁺(4-3)强度比值分布在环的东、西部(sim0.44 pm 0.04)高于环的南、北部(sim0.35 pm 0.03). HCN/HCO⁺(3-2)强度比值较高的区域(sim0.38 pm 0.04)分布在HCN(3-2)峰值位置, 而环的西北、东南部强度比值相对较低(sim0.3 pm 0.03). 对于中心不同区域 HCN/HCO⁺比值变化的原因进行了讨论.     

The Performance Evaluation of BeiDou-3 System Time Based on CGGTTS

According to the Common GNSS Generic Time Transfer Standard Version2E (CGGTTS_V2E) developed by the GNSS (Global Navigation Satellite System) Working Group of the International Consultative Committee for Time and Frequency (CCTF), the data processing software is developed by using the pseudorange signal measured by the GNSS receiver, which is used to generate the CGGTTS files in the standard format, and its reliability is verified. The results show that, compared with the CGGTTS files generated by sbf2cggtts software, the offset between the GNSS system time and local time scale calculated by the same GPS and BDS satellite observations in the same epoch is identical, and the difference with the absolute value of the difference less than 0.5 ns accounts for 96% and 94% of the total, respectively. Taking Chinese standard time UTC(NTSC) (Coordinated Universal Time (National Time Service Center)) as the reference time scale, the data processing software is used to process the observations of the B1I and B3I dual-frequency ionospheric combination of BeiDou-2 and BeiDou-3 satellites, and generate the CGGTTS files in the standard format, and the performance of BeiDou system time is evaluated by analyzing the parameter of offset between the GNSS system time and local time scale. The results show that, compared with BeiDou-2, the internal precision of BeiDou-3 system time is increased by about 28%, and the frequency stability of medium and long-term is obviously better than BeiDou-2 after one day.     

超级终端在自动站维护中的应用

利用W indow s操作系统中的超级终端检测、判断自动站采集器的状态,同时可对已缺测的正点数据进行补救。     

基于PSP观测的行星际Ⅲ型射电爆发的研究进展

与太阳射电爆发相比,通常认为频率较低的行星际射电爆发产生于远离低日冕的行星际空间.地球电离层的截止导致地基设备无法对其进行观测.美国国家航空航天局(National Aeronautics and Space Administration, NASA)发射的帕克太阳探测器(Parker Solar Probe, PSP)是迄今为止距离太阳最近的空间探测器.其搭载的射电频谱仪能够对10 k Hz–19.17 MHz频段范围内的射电辐射进行观测. PSP能够靠近甚至可能穿越行星际III型射电爆发的辐射源区,因此使用PSP对行星际射电爆发进行观测具有前所未有的优势.简要介绍了目前为止使用PSP的射电观测数据对行星际III型射电爆发的多方面研究,包括爆发的发生率、偏振、散射、截止频率、可能的辐射机制和相关的辐射源区等方面的研究进展,并讨论了其未来的研究前景.     

PhenoCrop: An integrated satellite-based framework to estimate physiological growth stages of corn and soybeans

The accurate and timely estimates of crop physiological growth stages are essential for efficient crop management and precise modeling of agricultural systems. Satellite remote sensing has been widely used to retrieve vegetation phenology metrics at local to global scales. However, most of these phenology metrics (e.g., green-up) are different from crop growth stages (e.g., emergence) used in crop management and modeling. As such, an integrated framework referred to as PhenoCrop was developed to: 1) establish a connection between remote sensing-derived phenology metrics and key crop growth stages based on Wang and Engle plant phenology model and 2) use fused MODIS-Landsat 30 m 8-day reflectance data generated using Kalman Filter-based data fusion technique to produce onset dates of key growth stages of corn (Zea mays L.) and soybeans (Glycine max L.) at 30 m spatial resolution. In this paper, we described the PhenoCrop framework, and tested its performance for the State of Nebraska for 2012–2016 by comparison to observations of estimated key growth stages at four experimental sites, and state-level statistical data from Crop Progress Reports (CPRs) published by the United States Department of Agriculture’s (USDA) National Agricultural Statistical Services (NASS). In addition, to evaluate the suitability of using coarse or high spatial resolution satellite imagery, fused MODIS-Landsat-based estimates were compared with those produced using EOS MODIS 250 m (MOD9Q1) reflectance data.The PhenoCrop estimates captured the typical spatial trends of gradual delay in the progression of the growing season from southeast to northwest Nebraska. Also inter-annual differences due to factors such as weather fluctuations and change in management strategies (e.g., early season in 2012) were evident in the estimates. Validation results revealed that average root mean square error (RMSE) of the state-level estimates of corn and soybean growth stages ranged from 1.10 to 4.20 days and from 3.81 to 7.89 days, respectively, while pixel level estimates had a RMSE ranging from 3.72 to 8.51 days for corn and 4.76–9.51 days for soybean growth stages. Although MODIS 250 m based estimates showed similar general spatial patterns observed in the fused MODIS-Landsat based estimates, the accuracy and ability to capture field scale variations was improved with fused MODIS-Landsat data. Overall, results showed the ability of PhenoCrop framework to provide reliable estimates of crop growth stages that can be highly useful in crop modeling and crop management during the growing season.     

天宫二号三维成像微波高度计大气斜距时延校正

2016-09-15随天宫二号空间实验室发射升空的三维成像微波高度计（简称天宫二号成像高度计）是国际上第一个采用小入射角、短干涉基线实现宽刈幅海面高度测量的高度计。由于天宫二号没有为成像高度计配备用于大气校正的微波辐射计,因此需要采用模型方法对大气时延进行精确估计。传统高度计采用星下点观测,通常只考虑大气折射率的改变引起传播速度变化的时延。天宫二号成像高度计采用偏离星下点1°—8°的小角度观测,因此在进行大气传输时延校正时不仅要考虑雷达信号传播速度的改变,还应考虑由于传播方向改变带来的路径弯曲效应。本文针对天宫二号成像高度计的观测几何特性,提出基于数值天气模型校正大气斜距时延的算法：采用欧洲中期天气预报中心的天气数据和大气分层模型,通过气象参数计算大气折射率;根据高度计参数和各层大气折射率,依赖折射定律和信号传播的几何关系在路径上逐层积分,计算大气斜距时延的估值。通过对天宫二号成像高度计的陆地角反射器定标实测数据进行处理,经大气斜距时延校正后,角反射器的剩余距离误差的标准差约为6.2 cm,达到厘米量级的斜距测量精度,验证了在不同入射角情况下,所提出的大气斜距时延校正算法的有效性和可靠性。