One-Centimeter Orbit Determination for Jason-1: New GPS-Based Strategies

The U.S./French Jason-1 satellite is carrying a state-of-the-art GPS receiver to support precise orbit determination (POD) requirements. The performance of the Jason-1 “BlackJack” GPS receiver was strongly reflected in early POD results from the mission, enabling radial accuracies of 1–2 cm soon after the satellite's 2001 launch. We have made further advances in the GPS-based POD for Jason-1, most notably in describing the phase center variations of the on-board GPS antenna. We have also adopted new geopotential models from the Gravity Recovery and Climate Experiment (GRACE). The new strategies have enabled us to better exploit the unique contributions of the BlackJack GPS tracking data in the POD process. Results of both internal and external (e.g., laser ranging) comparisons indicate that orbit accuracies of 1 cm (radial RMS) are being achieved for Jason-1 using GPS data alone.     

GPS制导技术浅析及对抗策略

GPS导航技术应用于武器精确制导,大大提高了武器的制导能力和打击精度。卫星制导武器已逐渐成为战争的主要打击兵器,推动着作战样式的新发展。通过对GPS／INS（惯性导航）组合制导技术进行分析,针对弱点提出了干扰对策。     

导航卫星自主定轨时轨道机动问题的处理方法

在各种摄动因素的作用下,导航卫星将逐渐偏离其预定轨道,因而需要通过轨道机动的方法来予以纠正。但轨道机动后,由预报轨道所提供的轨道先验信息将失去作用,这是用星间距离观测值和先验轨道信息进行导航卫星自主定轨时必须要解决的问题。提出机动后,机动卫星采用几何法来确定自己的位置,然后用动力学法来进行轨道拟合和轨道预报,在机动后第二天就能恢复正常的自主定轨。即使有多个卫星在同一天发生机动,个别卫星因可观测卫星不足4个而无法定轨,在第二天就能实现几何法定位,不会影响整个系统的导航定位功能。     

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GPS positioning accuracy using precise real‐time ephemeris and clock correction

Global positioning system (GPS) has found applications in various areas including marine geodesy. GPS positioning accuracy, however, is greatly degraded by GPS ephemeris and clock errors, particularly errors due to Selective Availability (SA). Thus, it is crucial to use precise ephemeris and clock corrections for users who require high position accuracy. Presently, precise ephemeris and clock corrections are available only in post‐mission. This paper investigates the generation of precise real‐time ephemeris and clock corrections and the positioning accuracy using them. In this research, precise real‐time ephemeris is generated from accurate dynamic orbit prediction and clock corrections are calculated using instantaneous GPS measurements. Numerical analysis using data from an actual GPS tracking network is performed that indicates use of precise ephemeris and clock corrections can improve the positioning accuracy to the one meter level. This accuracy is attainable in real‐time as the precise real‐time ephemeris and clock corrections become available in the future.     

基于原始观测值的单频精密单点定位算法

研究了一种基于GPS原始观测值的单频PPP算法。该算法通过增加电离层延迟先验信息、空间和时间约束的虚拟观测方程,将电离层延迟当作未知参数与其他定位参数一并进行估计来高效修正电离层延迟误差。通过使用全球178个IGS站1d的实测数据对本算法的收敛速度、定位精度和电离层VTEC的精度进行检验与分析。结果表明,该算法的收敛速度和稳定性均得到了改善,其静态单频单天PPP解的精度可达2~3cm、模拟动态单频单天PPP解的精度可达2~3dm,并且单频PPP与双频PPP提取的电离层总电子含量平均偏差小于5个TECU,可作为一种附属定位产品使用。     

GNSS观测值统一表达及组合PPP解算性能分析

针对GNSS多系统组合进行PPP定位的问题,推导了GNSS观测值统一表达式;进而给出了基于UofC模型的多系统组合PPP的函数模型和随机模型;最后采用6个IGS观测站24 h观测数据对7种组合模型的PPP进行解算,并从收敛率、收敛速度和定位精度等方面进行了统计分析。实验结果表明,当观测时长为60 min时,GPS/GLONASS/BDS组合PPP收敛性能最好,收敛率为91.7%,平均收敛时间为16.1 min;而BDS PPP收敛性能最差,收敛率仅为32.7%,平均收敛时间为38.4 min。可见,多系统组合有利于提高精密单点定位的解算性能。对于定位精度,在观测时长较短时(如0.5 h),GPS/GLONASS/BDS组合PPP整体上具有最优的定位精度,(N,E)方向偏差和标准差分别为(0.3,0.5)cm和(1.9,4.3)cm;短时间内对流层参数与垂直方向的强相关性,将致使U方向精度较差。     

基于全球MGEX数据的北斗导航星座精密轨道确定

利用全球分布的MGEX站观测数据,使用"两步法"以双差方式对北斗卫星进行精密定轨。主要研究北斗卫星轨道确定的处理策略,重点分析轨道确定的流程,并通过实验评价了3种不同类型轨道的精度。结果显示,MEO和IGSO卫星的定轨内符合精度优于0.2m,其中径向优于10cm,外符合精度优于30cm;GEO(以C05号为例)卫星外符合精度优于0.7m,且径向优于10cm。     

工业现场近景数字摄影视觉精密测量

研究了基于近景数字摄影原理的现场三维精密视觉测量方法,对其核心技术:数字成像器件模型及标定、高精度亚像素图像处理算法以及光学编码与精密测头技术进行了深入的讨论,给出了实现思路,为工业现场近景数字摄影精密测量系统的设计提供了理论依据。