利用SLR与伪距资料综合定轨

以GPS伪距为观测量对GPS35卫星进行定轨 ,然后将SLR与GPS伪距资料综合起来进行定轨 ,并将计算的轨道与IGS精密轨道进行了比较     

星蚀期北斗卫星轨道性能分析——SLR检核结果

星蚀期北斗卫星的轨道性能是北斗卫星导航系统性能分析的重要部分。了解北斗卫星导航系统星历中星蚀期轨道的精度,不仅可为系统服务性能评估提供支持,还有助于了解星蚀期精密定轨中相关模型可能存在的问题,进而为精密定轨函数模型改进提供参考。本文基于2014年1月至2015年7月的卫星激光测距资料,重点分析了星蚀期对北斗不同类型卫星轨道的影响,同时也对北斗广播星历和精密星历中整体轨道径向精度进行检核。结果表明:星蚀期内(尤其是偏航机动期间),IGSO/MEO卫星的广播星历和精密星历轨道均存在明显的精度下降;广播星历轨道径向误差达1.5~2.0m,精密星历轨道径向误差超过10.0cm。但仅从轨道径向残差序列中难以发现星蚀期对GEO卫星轨道是否有显著影响。非星蚀期间,IGSO/MEO卫星和GEO卫星的广播星历轨道径向精度分别优于0.5 m和0.9 m。IGSO/MEO卫星的精密星历轨道径向精度优于10.0cm,GEO卫星的轨道径向精度约50.0cm,且存在40.0cm左右的系统性偏差。     

Accuracy of mean earth ellipsoid based on Doppler,laser and altimeter observations

The error in the mean earth ellipsoid computer on the basis of Doppler or laser observations of artificial earth satellites or radar altimeter observations of the ocean surface from a satellite depends upon instrument precision, on uncertainties in the specification of the earth's gravity field at both long and short wave lengths, on uncertainties in the origin of the coordinate system, on modeling errors in ionospheric (except laser) and tropospheric refraction, and, for altimetry, on oceanographic effects. The magnitude of the uncertainty in the computed ellipsoid will vary depending on the size of these errors and on the number and distribution of observation stations. Review of computations based on various data sets indicates that differences in the computed ellipsoids are consistent with those expected due to the various error sources and that the best fitting ellipsoid has a semi-major axis of6378136±2 m.     

GPS/GLONASS/BDS广播星历轨道误差分析

针对GPS、GLONASS、BDS组合定位中观测值定权的问题,利用广播星历计算卫星位置,以IGS提供的精密星历为参考,将卫星坐标的三维均方根误差与附有加权因子的用户等效距离误差作为精度指标,对各系统轨道误差进行对比分析,找寻其规律。对2013、2014、2015各年8月份轨道误差进行分析,结果表明BDS系统在逐步完善,GPS/GLONASS/BDS 3系统轨道误差的权比在3年间显示出5∶2∶1、5∶2∶2、5∶2∶3的变化。以后的组合定位观测值可参考2015年的权比定权。     

GOCE gradiometer: estimation of biases and scale factors of all six individual accelerometers by precise orbit determination

A method has been implemented and tested for estimating bias and scale factor parameters for all six individual accelerometers that will fly on-board of GOCE and together form the so-called gradiometer. The method is based on inclusion of the individual accelerometer observations in precise orbit determinations, opposed to the baseline method where so-called common-mode accelerometer observations are used. The method was tested using simulated data from a detailed GOCE system simulator. It was found that the observations taken by individual accelerometers need to be corrected for (1) local satellite gravity gradient (SGG), and (2) rotational terms caused by centrifugal and angular accelerations, due to the fact that they are not located in the satellite’s center of mass. For these corrections, use is made of a reference gravity field model. In addition, the rotational terms are derived from on-board star tracker observations. With a perfect a priori gravity field model and with the estimation of not only accelerometer biases but also accelerometer drifts, scale factors can be determined with an accuracy and stability better than 0.01 for two of the three axes of each accelerometer, the exception being the axis pointing along the long axis of the satellite (more or less coinciding with the flight direction) for which the scale factor estimates are unreliable. This axis coincides with the axis of drag-free control, which results in a small variance of the signal to be calibrated and thus an inaccurate determination of its scale factor in the presence of relatively large (colored) accelerometer observation errors. In the presence of gravity field model errors, it was found that still an accuracy and stability of about 0.015 can be obtained for the accelerometer scale factors by simultaneously estimating empirical accelerations.     

四大GNSS广播星历精度评估与对比分析

分析了 目前广播星历精度评估中存在的问题,详细论述了广播星历精度评估过程中对精密星历进行天线相位中心改正的取值方法,提出了利用单颗星单日钟差均值作二次差对广播星历钟差的系统性偏差进行改正的方法.选取2019-09-01-2019-11-01 共计62天的多模 GNSS 实验(multi-GNSS experiment,...     

Improved GRACE science results after adjustment of geometric biases in the Level-1B K-band ranging data

The GRACE (Gravity Recovery and Climate Experiment) satellite mission relies on the inter-satellite K-band microwave ranging (KBR) observations. We investigate systematic errors that are present in the Level-1B KBR data, namely in the geometric correction. This correction converts the original ranging observation (between the two KBR antennas phase centers) into an observation between the two satellites’ centers of mass. It is computed from data on the precise alignment between both satellites, that is, between the lines joining the center of mass and the antenna phase center of either satellite. The Level-1B data used to determine this alignment exhibit constant biases as large as 1–2 mrad in terms of pitch and yaw alignment angles. These biases induce non-constant errors in the Level-1B geometric correction. While the precise origin of the biases remains to be identified, we are able to estimate and reduce them in a re-calibration approach. This significantly improves time-variable gravity field solutions based on the CNES/GRGS processing strategy. Empirical assessments indicate that the systematic KBR data errors have previously induced gravity field errors on the level of 6–11 times the so-called GRACE baseline error level. The zonal coefficients (from degree 14) are particularly affected. The re-calibration reduces their rms errors by about 50%. As examples for geophysical inferences, the improvement enhances agreement between mass variations observed by GRACE and in-situ ocean bottom pressure observations. The improvement also importantly affects estimates of inter-annual mass variations of the Antarctic ice sheet.     

低轨卫星初始状态误差对反演地球重力场的影响

基于动力学法反演地球重力场的基本理论,研究了卫星初始状态向量误差对应用低轨卫星精密轨道数据反演地球重力场的影响。在仅考虑低轨卫星初始状态误差的情况下进行了模拟计算,结果表明:在利用低轨卫星精密轨道数据反演地球重力场时,卫星初始状态向量误差需要重新进行估计;在目前的轨道精度水平下,若不顾及误差方程二次项的影响,反演弧长不宜过长;卫星初始状态速度误差(约1.5mm/s)的影响要大于位置误差(约10 cm)的影响。     

GPS卫星轨道数值积分与广播星历及IGS精密星历的比较

本文采用作者自编的SPPORB IT程序,对GPS卫星轨道的运动方程进行Adam s数值积分求解,同时利用广播星历计算卫星轨道坐标,然后将两者结果同IGS精密星历提供的卫星坐标进行比较,并探讨其轨道误差,计算结果显示广播星历与精密星历差值在2m左右,而数值积分与精密星历的差值在2 cm左右,进一步的分析表明前者误差较大是没有考虑卫星所受的太阳光压、日月引力等影响,而后者考虑了这些影响。鉴于IGS提供的是地固系坐标,而本文数值积分是在惯性系坐标系下进行的,因此本文还举例对惯性坐标系和地固系之间的坐标转换进行了描述。最后,通过实例说明SPPORB IT程序的稳定性以及Adam s数值积分方法的有效性。     

基于道路的地球同步卫星定位方法误差分析

针对基于道路的地球同步卫星定位方法，分析了几种主要的误差源（测距误差，星历误差，中心站站址误差和道路数据库误差）对定位精度的影响特点，从而给出院 系统本身的定位精度及对道路数据库的精度要求，理论分析表示，测距误差，星历误差是影响用户平面精度的主要因素，而道路数据库的高程误差是影响用户高程精度的主要因素，另外，也进一步验证了该方法的可行性和可靠性。     

GPS/BDS卫星摄动力数值分析

由精密星历利用拉格朗日插值公式求二次导数的方法计算了卫星在J2000.0惯性坐标系下的总加速度;利用现有的力模型计算了地球中心引力,地球非球形摄动力,太阳、月球和其他行星的摄动力,地球固体潮摄动力,相对论效应摄动力对GPS/BDS卫星所产生的加速度数值大小;利用G-file里的BERNE太阳光压模型参数计算了GPS卫星太阳光压摄动加速度大小;对GPS/BDS卫星所受的不同摄动力进行了数值分析,对同一摄动力对不同类型卫星的影响进行了数值分析比较。结果表明,现有力模型与GPS/BDS卫星所受的实际作用力仍有一定的差距,不同类型卫星所受摄动力有明显差异,在精密定轨的实际应用中应根据不同类型卫星建立合适的力学模型。     

VLBI、卫星网和地面网联合平差的数学模型

本文同时顾及地面网尺度系统误差和卫星网尺度系统误差对各自网点坐标的影响,对联合平差中常用的两种7参数转换模型:Bursa模型和Molodensky模型进行了分析比较,在此基础上,提出了一种新的7参数转换模型;建立了甚长基线(VLBI)、卫星网和地面网联合平差的数学模型,并用模拟数据进行了数值分析,得到了一些有益结论。     

基于IGS精密星历的完备性监测指标SISA研究

在卫星导航定位系统中,空间信号精度SISA是反映完备性参数的重要指标之一。从SISE与SISA的基本概念出发,描述了SISA的计算算法,根据卫星星钟的不同,选取了不同类型的GPS卫星,并利用IGS精密星历,预报精密星历进行了SISE和SISA的计算,结果表明:IGR星历计算的SISA指标满足系统要求,SISA主要受卫星钟差的精度影响,不同原子钟类型的卫星计算出来的SISA值变化不大。该成果对于卫星导航的完备性监测数据处理具有参考意义。     

快速星历代替最终星历的可行性研究

精密单点定位中卫星星历误差和卫星钟差是影响定位精度的重要误差。基于传统的消电离层模型,编制相应的程序,然后对目前IGS提供的2种精密星历（IGF、IGR）及其钟差进行实验分析。结果表明,快速星历及其钟差可以代替最终星历及其钟差进行定位。     

A parametric study on the impact of satellite attitude errors on GOCE gravity field recovery

In the recent design of the Gravity field and steady-state Ocean Circulation Explorer (GOCE) satellite mission, the gravity gradients are defined in the gradiometer reference frame (GRF), which deviates from the actual flight direction (local orbit reference frame, LORF) by up to 3–4°. The main objective of this paper is to investigate the effect of uncertainties in the knowledge of the gradiometer orientation due to attitude reconstitution errors on the gravity field solution. In the framework of several numerical simulations, which are based on a realistic mission configuration, different scenarios are investigated, to provide the accuracy requirements of the orientation information. It turns out that orientation errors have to be seriously considered, because they may represent a significant error component of the gravity field solution. While in a realistic mission scenario (colored gradiometer noise) the gravity field solutions are quite insensitive to small orientation biases, random noise applied to the attitude information can have a considerable impact on the accuracy of the resolved gravity field models.     

关于广播星历轨道误差的探讨

通过利用广播星历中的开谱勒轨道参数与轨道摄动修正量计算卫星轨道坐标与精密星历的轨道信息进行比较 ,探讨广播星历的轨道精度。     

激光在天空对地观测中的应用

1960年7月世界上第一台激光器问世后，激光测距迅速兴起，不管是地面激光测距，还是激光测卫和激光测月，都为大地测量学的发展作出了重大贡献；特别是激光测卫测月成果，为我们深化对地球动态效应的认识，揭示地球的奥秘，提供了许多重要的科学数据，本文综析了值得注视的下列新近发展。.在IGEX-98国际大联测中，求定GLONASS卫星的激光轨道与微波轨道之差；.评定PRN05/06号GPS卫星星历的精度；.检核Topex/Poseidon海洋测高卫星用GPS定轨的测量误差，.用机载激光测深系统测量海水的浓度；.用EOS-ALT星载激光测距/测高系统测量地球动态参数。     

GNSS广播星历轨道和钟差精度分析

为了对多个全球导航卫星系统（global navigation satellite system,GNSS）当前的广播星历精度进行一个全面的分析,对比了2014—2018年共5 a的GNSS广播星历与精密星历,并对全球定位系统（global positioning system,GPS）、格洛纳斯卫星导航系统（global navigation satellite system,GLONASS）、伽利略卫星导航系统（Galileo satellite navigation system,Galileo）、北斗卫星导航系统（BeiDou navigation satellite system,BDS）、准天顶卫星系统（quasi-zenith satellite system,QZSS）等5个系统的广播星历长期精度变化进行了分析。结果表明：5 a中GPS的广播星历轨道及钟差精度最稳定;GLONASS的广播星历轨道精度稳定性较好,但其钟差精度存在较大的离散度;Galileo得益于具备全面运行能力（full operational capability, FOC）卫星的大量发射及运行,其广播...     

太阳活动对GPS卫星广播星历的影响

采用了切比雪夫拟合多项式内插IGS精密星历,计算了GPS卫星广播星历轨道误差,比较了其在太阳活动谷值和峰值时的误差,讨论了其与太阳活动状况的关系。     

不同参考基准精密星历对单点定位的影响

精密单点定位的实质就是利用精密星历和精密卫星钟改正来实现定位。但是IGS不同分析中心提供的精密星历和卫星钟改正数的基准不一致,如果使用不同分析中心提供的精密星历和卫星钟差就会对定位精度产生影响。本文采用IGS精密星历和JPL精密星历,使用相同的IGS精密卫星钟差,分别计算对测站坐标精度的影响。