Demonstration on the indexes design of gravity satellite orbit parameters in the low-low satellite-to-satellite tracking mode

Combining with the exigent demand of the development of satellite gravimetry system in China, aiming at the determination of technical indexes of gravity satellite orbit parameters, on the basis of the numerical experiments and results analysis, the design indexes of gravity satellite orbit height, inter-satellite range and the orbit inclination are analyzed and calculated, and the issues towards twin gravity satellites such as coherence requirement of the orbit semi-major axes, control requirement of the pitch angle and time interval requirement to keep twin satellites formation in mobility are diseussed. Results show that the satellite orbit height is 400 km to 500 km, the inter-satellite range is about 220 km, the satellite orbit inclination is between polar orbit and sun-synchronous orbit, the semi-major axes difference of twin satellites orbit is within ± 70. 146 m, the pitch angle of twin satellites is about 0.9 degree, and the time interval to keep twin satellites formation in mobility is 7 days to 15 days.

THE RELATIONSHIPS BETWEEN TROPICAL CYCLONE TRACKS AND LOCAL SST OVER THE WESTERN NORTH PACIFIC

Tropical Cyclone (TC) tracks over the western North Pacific (WNP) during 1949–2007, obtained from China Meteorological Administration/Shanghai Typhoon institute, are classified into three track types. These types are the main pathways by which TCs influence the coast of East Asia. The relationships between local sea surface temperature (SST) in WNP and TC tracks are revealed. Results show that the local SST plays an important role in TC tracks, though the relationships between local SST and the frequencies of different TC tracks are very dissimilar. The local SST has significant positive correlation with northwest-path TCs, and negative correlation with recurving-path TCs. However, the west-path TCs do not have statistically significant relationship with the local SST. The upper sea temperature anomalies which influence TC tracks last about six months before TC occurrence. Further analysis indicates that the ocean conditions influence TC tracks by modifying the atmospheric circulation, and then the modified atmospheric circulation can affect TC’s genesis location and motion.

Impacts of Increased SST Resolution on the North Pacific Storm Track in ERA-Interim

This study examines the artificial influence of increasing the SST resolution on the storm track over the North Pacific in ERA-Interim.Along with the mesoscale oceanic eddies and fronts resolved during the high-resolution-SST period,the low-level storm track strengthens northward,reaching more than 30%of the maximum values in the low-resolution-SST period after removing the influence of ENSO.The mesoscale structure firstly imprints on the marine atmospheric boundary layer,which then leads to changes in turbulent heat flux and near-surface convergence,forcing a secondary circulation into the free atmosphere,strengthening the vertical eddy heat,momentum and specific humidity fluxes,and contributing to the enhancement of the storm track.Results from a high-resolution atmospheric model further indicate the changes in the storm track due to the mesoscale SST and their relationship.

Interannual and Decadal Variability of the North Pacific Blocking and Its Relationship to SST, Teleconnection and Storm Tracks

Climalological features of mid-latitude blocking occurring over the North Pacific Ocean during 52 winters (December to February) of 1948/1949-1999/2000 are statistically analyzed based on NCEP/ NCAR reanalysis data. Significant interannual variation with a period of about 3-7 years as well as decadal variability is found by wavelet analysis and power spectrum analysis. A decreasing trend of the 2-7 year bandscale-averaged variance occurs throughout the 52 years and an abrupt shift from a higher state to a lower state during the 1970s is also found, which suggests an interdecadal variation of the North Pacific blocking. The possible relationship between the variability of blocking and sea surface temperature (SST), storm tracks and teleconnection are shown using composite analysis. In strong blocking anomaly winter (SBW), the geopotential height anomaly at 500 hPa exhibits a typical PNA (Pacific-North American)-like wave-train pattern in the North Pacific. The storm tracks, representing the activity of transient eddies, extend northeastward to the western coast of North America along the mid latitudes of about 40°-50°N, with the SST anomaly exhibiting a Pacific decadal oscillation (PDO) mode at mid-latitude and a La Niña-like pattern along the equator. Contrasting features appear in weak blocking anomaly winter (WBW).

A preliminary study of level 1A data processing of a low-low satellite to satellite tracking mission

With the Gravity Recovery and Climate Experiment {GRACE） mission as the prime example, an overview is given on the management and processing of Level IA data of a low-low satellite to satellite tracking mission. To illustrate the underlying principle and algorithm, a detailed study is made on the K-band ranging （KBR） assembly, which includes the measurement principles, modeling of noises, the generation of Level 1A data from that of Level 0 as well as Level IA to Level IB data processing.

北太平洋东部风暴轴的变化特征及其与大气环流和SST异常的关系

利用欧洲中期天气预报中心ECMWF(European Center for Medium-range Weather Forecast)逐日再分析资料(ERA40),通过经验正交函数(empirical orthogonal function,EOF)分解发现,冬季北太平洋东部风暴轴有着显著的年际变化特征:第一变化模态为在气候平均位置南北相反的偶极子变化型,第二变化模态为在气候平均位置处一致增强或减弱的变化型,第三变化模态为三极子的变化型。进一步的回归分析发现:当东部风暴轴南压(北抬)时,同期冬季是一种厄尔尼诺(拉尼娜)年海温异常空间分布型,中纬度北太平洋海区以及赤道中、东海区,冬季冷(暖)异常的洋面上是异常低压(高压),对流层中层是太平洋—北美型(Pacific-North American Pattern,PNA)遥相关的正(负)位相;当东部风暴轴增强(减弱)时,同期冬季黑潮区海温偏暖(偏冷),对流层中层表现为西太平洋型(West Pacific Pattern,WP)遥相关的正(负)位相;当东部风暴轴呈现西北—东南+-+(-+-)相间三极子的分布时,同期冬季巴布亚新几内亚附近海温异常偏暖(冷),夏威夷附近海温异常偏冷(暖),冬季冷(暖)异常的洋面上是异常低(高)压,对流层中层表现出类似PNA正(负)位相。EOF分解各模态所对应时间系数与阿留申低压(Aleutian Low,AL)指数、PNA指数、Nino3指数、WP指数、黑潮海温(Kuroshio Current,KC)指数之间存在显著的相关,这些证明了东部风暴轴与同期大气环流及SST异常之间的联系。

精化地球重力场模型中SST距离的观测方程

在卫星受摄运动分析的基础上,给出了在利用卫星跟踪卫星(SST)精化地球重力场模型中,SST卫星之间距离的观测方程,实际上是地球引力位的一阶导数。

SST-11重力卫星轨道参数指标设计论证

本文结合我国发展卫星重力测量系统的需求，针对如何确定重力卫星轨道参数的技术指标问题，以数值实验为手段，分析并计算了重力卫星轨道高度、卫星星间距离和卫星轨道倾角的设计指标，讨论了两颗重力卫星轨道长半轴的一致性要求、姿态俯仰角的控制要求以及编队保持机动的时间间隔要求。结果表明，我国将来低低跟踪模式中重力卫星的轨道高度应在400～500km之间，星间距离应为220km左右，卫星轨道倾角应该位于极轨和太阳同步轨道之间，双星轨道的长半轴之差需要控制在±70m的范围之内，双星的姿态俯仰角应控制在0．9。左右，双星编队保持机动的时间间隔要求在7一15天之间。

基于SST的无砟轨道离缝缺陷识别方法研究

无砟轨道离缝缺陷是高速铁路运营过程中常见病害形式。针对弹性波在高速铁路无砟轨道层状结构中传播路径复杂,轨道板与功能层之间的离缝缺陷检测困难,构建带离缝缺陷的层状混凝土结构模型,分析弹性波在无砟轨道结构中的时域传播特性和显著性频域特征;研究系统噪声对缺陷回波信号频谱分析的影响,剖析同步挤压小波变换(SST)原理及其时频分辨率,进而提出层状结构弹性波信号处理和离缝缺陷识别方法。数值模拟试验和现场试验表明,基于SST方法,可有效降低系统噪声和结构噪声的干扰,实现离缝缺陷回波显著频域提取,提高无砟轨道离缝缺陷识别精度。

SST-ll重力卫星轨道运动对K波段测距系统的影响

给出了物体作近圆椭圆轨道运动的近似运动学方程,并结合GRACE重力卫星的轨道参数,在没有考虑摄动效应的前提下,计算了双星的距离、相对速度以及双星连线的倾角,并讨论了这些量对K波段测距系统的影响。同时分析表明,2倍轨道频率的效应可望用于K波段测距和测速的在轨性能检验,这对于K波段研究具有一定指导意义。

Comparison of Present SST Gravity Field Models

Taking the main land of Europe as the region to be studied, the potential of the new satellite gravity technique: satellite-to-satellite tracking (SST) and improving the accuracy of regional gravity field model with the SST models are investigated. The drawbacks of these models are discussed. With GPM98C as the reference, the gravity anomaly residuals of several other models, the latest SST global gravity field models (EIGEN series and GGM series), were computed and compared. The results of the comparison show that in the selected region, some systematic errors with periodical properties exist in the EIGEN and GGM’s S series models in the high degree and order. Some information that was not shown in the classic gravity models is detected in the low and middle degree and order of EIGEN and GGM’s S series models. At last, the effective maximum degrees and orders of SST models are suggested.

模拟研究卫-卫跟踪中星间隔的选择问题

从两个方面讨论了低轨卫星在做卫-卫跟踪(SST)观测时,星间隔的选择问 题. 1)用地球重力位系数作为扰动量,比较该扰动引起的不同间隔的SST星间距离和速 度变化大小. 2)用随机误差为1μm／s的星间速度变化作为模拟观测量,恢复不同间隔的 地球重力位系数,并做精度评估.两种结果表明,适当增大SST间隔对求解重力场有利, 但无限制增大无实际意义,对于选定高度为420 km卫星,在作SST观测时,星间隔不宜 超过690km.此模拟方法及结果对我国确定重力卫星指标有着重要意义.

日本SELENE月球探测计划和卫星间多普勒跟踪的数学模型

日本月球探测计划（ＳＥＬＥＮＥ）定于２００４年夏季利用ＨＩＩａ火箭发射一组共３颗绕月人造卫星。他们是主卫星、跟踪中继卫星和空间ＶＬＢＩ电波源。其主要科学目标之一是利用对绕月卫星的多普勒跟踪数据精确测定月球重力场，研究月球的起源与演化。ＳＥＬＥＮＥ计划中实现这个科学目标的关键技术是引入中继卫星，目的在于当处于低轨道的主卫星飞行到月球背面地面观测站无法观测时，采用卫星间跟踪方法（ＳＳＴ），建立地面站与主卫星之间的联系，以得到月球背面重力场的直接测量数据。介绍了几种典型的四程卫星间多普勒跟踪模式和相应的数学模型，并针对ＳＥＬＥＮＥ计划中采用的特殊四程多普勒跟踪模式建立了卫星相对观测站速度与跟踪信号多普勒频移之间的转换关系。提出了利用 ＧＥＯＤＹＮ ＩＩ定轨分析软件处理ＳＥＬＥＮＥ多普勒跟踪数据的流程。

海洋表层温度对台风“蔷薇”路径和强度预测精度的影响

基于中尺度大气模式WRF(Weather Research and Forecasting Model),首先对2007年3次船舶辐射通量观测进行模拟,以检验WRF对长波和短波辐射通量的模拟能力,结果表明使用中国近海海洋环境数值预报系统环流模式POM(Princeton Ocean Model)模拟的高时空分辨率的海洋表层温度能够显著改进短波辐射通量的模拟,而对长波辐射通量模拟的改进不明显。然后,将业务化运行的中国近海海洋环境数值预报系统后报的逐时海洋表面温度(SST)作为WRF底边界条件,对2008年15号强台风"蔷薇"(Jangmi)过程进行了数值后报试验。结果表明,与使用NCEP/NCAR的SST试验后报的台风中心位置偏差相比,使用高时空分辨率的SST能够较为显著地改善"蔷薇"的路径模拟,台风中心位置模拟偏差减少11%,尤其在台风减弱阶段,台风中心位置模拟偏差减少37%。台风强度在台风发展的不同阶段对下垫面SST的变化敏感性不同。台风路径附近的海表面温度下降会导致海洋向大气输送的热量减少从而减弱台风强度。

一种新型重力测量卫星系统确定全球重力场的性能分析

本文设计了一种高-低卫星跟踪卫星、低-低卫星跟踪卫星和卫星重力梯度测量相结合的新型重力测量卫星系统,其可在一定程度上发挥卫星重力梯度和低低卫星跟踪卫星两种测量模式各自的优势.基于重力卫星系统指标设计的半解析法,深入分析了不同重力测量卫星系统配置和不同观测量及其不同白噪声水平情况下,新型卫星重力测量模式反演重力场模型的能力.数值模拟分析结果表明:在观测值精度和星间距离相同的条件下,轨道高度是影响重力场反演精度的关键因素;随着星间距离的增大,高频重力场信号反演精度会先提高后降低,轨道高度在200~350km之间时,星间距离在150~180km之间时反演精度最优;星间距离变率和卫星重力梯度两类观测值仅在某些精度配置时可达到优势互补,如果某一类观测值精度很高,则另一类观测值在联合解算时贡献非常小或者没有贡献.在300km轨道高度,若以GRACE和GOCE任务的设计指标1μm·s-1/(Hz)^(1/2)和5mE/(Hz)^(1/2)来配置新型重力测量卫星系统中星间距离变率和引力梯度观测值的精度,联合两类观测值解算200阶次模型大地水准面的精度比独立解算分别提高1.2倍和2.8倍.如果以实现100km空间分辨率1~2cm精度大地水准面为科学目标,考虑卫星在轨寿命,建议轨道高度选择300km,星间距离变率和卫星重力梯度的精度分别为0.1μm·s-1/(Hz)^(1/2)和1mE/(Hz)^(1/2).本文的研究成果可为中国研制自主的重力测量卫星系统提供参考依据.

海温变化对台风路径的影响

在台风模式中采用周平均海温和多年的月平均海温 ,对一些台风个例进行了比较。

卫星星座整网轨道确定分析与仿真(英文)

编队飞行的卫星或卫星星座对轨道确定自主性和精度提出了较高要求。针对这个问题,通过建立星座的轨道动力学模型和星间观测的测量模型,将星座中的星间观测数据和地面观测数据融合起来,将待估的卫星轨道参数和部分动力学参数进行适当的分类,研究卫星星座整网轨道确定的新方法,并在理论上分析了整网定轨方法能提高定轨精度的原因;最后采用自主开发的卫星星座整网轨道确定软件进行了仿真计算。计算表明,该方法能有效地减少对地面站的依赖,并较大幅度提高定轨时卫星绝对位置和相对位置精度。

GOCE卫星重力探测任务

通过分析利用卫星观测技术恢复地球重力场的现状与不足,论述了实施GOCE任务———地球重力场和稳态海洋环流实验的必要性;并阐述了GOCE任务的发展历史及现状、基本特点、组成部分、重力梯度测量原理、数据处理过程、误差特性,以及该任务在固体地球物理学、大地测量学、海洋学、冰河学等地球物理相关科学领域中的应用。

联合不同类型重力测量数据确定地球重力场模型的迭代法

不同的重力测量数据包含了不同波段的地球重力场信息,因此要恢复更高精度的地球重力场模型,就必须对不同类型的重力测量数据进行联合处理.以地面重力异常Δg为例,推导了利用迭代法联合不同类型重力测量数据反演地球重力场模型的基本原理公式,并给出了其具体实现步骤,接着采用全球的重力异常Δg数据和扰动位T数据,基于迭代法对卫星重力梯度SGG数据解算的重力场模型进行了进一步的精化.结果表明,初始的卫星重力梯度SGG模型和经过全球重力异常Δg数据精化后的模型,其对应的累计大地水准面误差分别达到1.128cm和0.048cm、累计重力异常误差分别达到0.416mGal和0.018mGal的精度;在经过全球扰动位T数据进一步精化后的模型,其对应的累计大地水准面误差达到0.043cm、累计重力异常误差达到0.016mGal的精度.

卫星重力探测技术与地球重力场研究

这是一篇综述性的文章 ,主要阐述了两个问题 :一是概述了 4种卫星重力探测技术的概念、发展情况和应用结果 ;二是阐述了基于卫星重力数据的地球重力场研究在理论和方法上应考虑的若干问题。