Co-location of Geodetic Observation Techniques in Space
Co-location of Geodetic Observation Techniques in Space
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DOI：
10.3929/ethz-a-010811791
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发表时间：
2016
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影响因子：
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通讯作者：
Benjamin Männel
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作者：
Benjamin Männel
本文介绍了卫星上大地测量观测技术的组合。这种所谓的空间同地定位在实现长期、准确和稳定的地面参照基准所需的改进方面提供了相当大的潜力。空间关系（即，机载传感器之间的集合矢量）在不同空间大地测量技术的传感器之间引入了新的几何连接。通过空间大地测量观测，可以很容易地为每个基本站点提供这种空间联系。因此，空间共址允许评估技术特定的误差源，因为系统效应可以针对某个站或某个技术。此外，引入的额外轨道动力学改进了对若干大地测量参数的估计。本论文讨论了空间共定位的核心问题：轨道确定、地面和空间GNSS观测的结合以及VLBI地球轨道卫星跟踪。高度精确的轨道确定是适当的空间共址的先决条件。基于GRACE、GOCE和OSTM/Jason-2对地观测卫星任务，研究了非引力摄动建模的影响。总体达到的轨道精度为几厘米。基于53个地面站和4个低地球轨道卫星（LEO）的GPS观测数据，研究了地面和空间大地测量GNSS观测数据的组合。在仅地面处理中添加一个LEO可将每周地心估计的形式误差降低约20%，由于观测数量增加，这是预期的八倍。这表明地面数据和低地球轨道数据相结合的巨大潜力。从卫星激光测距（SLR）的结果与推导出的地心时间序列进行比较，显示出良好的协议，每年的振幅，而每年的阶段显示出相当大的差异，在x和z分量。从长期解中估计的表面载荷密度系数得到的地心坐标与SLR解的结果吻合得更好，但没有额外LEO的显著影响。利用地球引力约束，利用地面和低轨卫星观测数据估计GPS卫星天线相位中心。结果表明，引入LEO有助于消除极限相关，对水平O集有显著的贝内。针对单频VLBI卫星跟踪问题，介绍了基于GNSS共址观测的L4 R方法，推导了电离层延迟改正量。在引入L4 R校正的同时，在单频GNSS处理中实现了每天1 cm的站坐标重复性。从VLBI观测得到的电离层延迟的差异也显示出很好的一致性。由于VLBI卫星跟踪目前还处于试验阶段，因此对8种不同的卫星轨道类型进行了蒙特-卡罗模拟。对于全球导航卫星系统星座跟踪，区域和全球网络的台站坐标重复性分别为0.7和1.2厘米。对一个高度为2000 km的近地轨道卫星进行VLBI模拟观测，得到了约1 cm的台站坐标重复率。由E-GRIP和E-GRASP/Eratosthenes模拟观测估计的台站坐标显示出较大的不确定性。根据这些结果，拟订了关于空间同地办公的未来行动项目的建议。最重要的建议是，地面和空间全球导航卫星系统观测相结合，为确定若干参数提供了相当大的贝内，电离层延迟校正应根据共址全球导航卫星系统观测得出。
This thesis describes the combination of geodetic observation techniques on-board satellites. This socalled co-location in space provides a considerable potential regarding the improvements needed to realize a long-term accurate and stable terrestrial reference frame. The space ties (i.e., the o set vectors between the on-board sensors) introduces new geometrical connections between sensors of di erent space geodetic techniques. This space ties can be provided easily to each fundamental site via space geodetic observations. Consequently, co-location in space allows to assess technique-speci c error sources as systematic e ects can be addressed either to a certain station or to a certain technique. Moreover, the additional introduced orbit dynamics improve the estimation of several geodetic parameters. Within this thesis the following core topics concerning co-location in space are discussed: orbit determination, the combination of ground and space GNSS observations, and VLBI Earth-orbiting satellite tracking. Highly accurate orbit determination is the prerequisite for a suitable co-location in space. Based on the Earth observation satellite missions GRACE, GOCE, and OSTM/Jason-2 orbit determination and the impact of modeling non-gravitational perturbations is studied. The overall reached orbit accuracies are at the level of a few centimeters. The combination of ground and space-geodetic GNSS observations is studied based on the GPS observations derived by 53 ground stations and the four LEOs (low Earth orbiter). Adding one LEO to the ground-only processing decreases the formal errors of weekly geocenter estimates by around 20% which is eight times more than expected due to the increased number of observations. This shows the considerable potential of the combination of ground and LEO data. Comparing the derived geocenter time series against results from satellite laser ranging (SLR) shows a good agreement for annual amplitudes, whereas the annual phases shows considerable discrepancies in the xand the z-component. Geocenter coordinates derived from surface load density coe cients estimated in a long-term solution show a better agreement to SLR solutions but without a signi cant impact of additional LEOs. Using the gravitational constraint GPS satellite antenna phase center o sets were estimated based on ground and LEO observations. The results show a signi cant bene t for the horizontal o sets as the introduced LEOs help to dissolve limiting correlations. Concerning single-frequency VLBI satellite tracking the L4R method is introduced to derive ionosphere delay corrections based on co-located GNSS observations. A 1 cm daily station coordinate repeatability is achieved in a single-frequency GNSS processing while introducing the L4R corrections. Di erences to ionospheric delays derived from VLBI observations show also a good agreement. As VLBI satellite tracking is currently in an experimental stage Monte-Carlo simulations were performed for eight di erent satellite orbit types. For a GNSS constellation tracking, station coordinate repeatabilities are at the level of 0.7 and 1.2 cm for a regional and a global network, respectively. Station coordinate repeatabilities of around 1 cm were derived for simulated VLBI observation to a ctitious LEO with an altitude of 2000 km. The station coordinates estimated from simulated observations to E-GRIP and E-GRASP/Eratosthenes show larger uncertainties. Based on the results suggestions for future action items regarding co-location in space were formulated. The most important recommendations are, that the combination of groundand space GNSS observations provides a considerable bene t for the determination of several parameters and that ionosphere delay corrections should be derived from co-located GNSS observations.