Precise Orbit Determination of Global Navigation Satellite System of ...

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Chapter 9 Software and Simulation Results Difference (meter) 10 10 8 6 4 2 0 -2 -4 -6 -8 -10 0 24 48 72 96 120 144 168 192 216 240 8 6 4 2 0 -2 -4 -6 -8 -10 Tim e (hour) Figure 9-19 Accuracy of Orbit Determination of a GEO Satellite Located at λ=20° 0 24 48 72 96 120 144 168 192 216 240 Figure 9-20 Accuracy of Orbit Determination of a GEO Satellite Located at λ=60 The accuracy of x, y, z coordinates of dynamic orbit determination of a GEO satellite located at λ=-10° are ±0.09, ±0.09 and ±0.13 meters respectively. The accuracy of a GEO satellite located at λ= 20° are ±0.15, ±0.16 and ±0.13 meters respectively. The accuracy of a GEO satellite located at λ=60° are ±0.24, ±0.25 and ±0.14 meters respectively. Also considering the unmodeling errors in the satellite dynamic models, the propagation and some unknown errors, 1-10 m accuracy-level of dynamic orbit determination of GEO satellites can be achieved using range observations with 1 m errors. Obviously, the accuracy of dynamic orbit determination of GEO satellites is better than that of IGSO satellites. This is related to satellite visibility, refer to Figure 9-5 to Figure 9-8. 9.3 Simulation Results using Carrier Observations In order to carry out the simulation of dynamic orbit determination of IGSO and GEO satellite using carrier phase observation, a theoretical error-free orbit is produced using a numerical integration method. Four major 122 dx dy dz dx dy dz
Chapter 9 Software and Simulation Results perturbation effects on the satellite orbit such as geopotential attraction (n, m ≤ 10), solar and lunar attraction and solar radiation pressure are included in the satellite dynamic model. The observation is a one-way carrier phase that is generated from the integrated theoretical orbit and the known coordinates of tracking stations described in §9.1.2. The white noise with σ = ±1 cm are added to carrier phase observation. The elevation cut-off angle of observation is 15°. The sample rate is 10 minutes. When observations are discontinuous due to the elevation mask limitation, new ambiguities of carrier phase observations will be added and solved during the orbit determination process. In the satellite dynamical models of orbit determination, the perturbation effects included are the same as those used for the theoretical error-free orbit integration, but there is a difference, for example, the degree and order of geoperturbation used in orbit determination are less than those used to determine the theoretical orbit. The accuracy of orbit determination is obtained using differences between the results of orbit determination and the theoretical error-free integration orbit. 9.3.1 Orbit Determination with Float Ambiguity Solution 9.3.1.1 The Accuracy of Orbit Determination without Satellite Visibility Considered The distribution of tracking stations used for orbit determination using carrier observations are drawn in Figure 9-2. In the following simulation results, the carrier phase observations are assumed to be continuous. The satellite visibility problem and cycle slips are not considered. All observations have to be set with true initial ambiguities according to their tracking stations as listed in Table 9-2. Table 9-2 TRUE INITIAL AMBIGUITY SET FOR TRACKING STATIONS Tracking Station True Initial Ambiguity Set(Cycles) Herstmonceux 20 Azoren 40 Kreta 60 Maspalomas 80 Kourou 100 Libreville 120 Hartebeesthoek 140 Perth 160 Float ambiguity solutions of IGSO satellite located at λ = -10° are shown in Figure 9-21 to Figure 9-28. Ambiguity 21 20.8 20.6 20.4 20.2 20 19.8 19.6 19.4 19.2 19 0 24 48 72 96 120 144 168 192 216 240 Tim e (hour) Figure 9-21 Float Ambiguity Solution of Tracking Station 1 123
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PRECISE ORBIT DETERMINATION OF GLOB
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Summary GNSS-2 (Global Navigation S
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3.2.2.1 Principle..................
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9.3.3 The Effect of Distribution of
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Chapter 1 Introduction 1.2 Developm
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Chapter 2 Observations of Orbit Det
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Chapter 3 Orbit Tracking System and
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Chapter 4 Major Error Sources of Sa
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Chapter 5 Perturbation Models of IG
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Chapter 6 Algorithms of Orbit Deter
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Page 154 and 155: References Carpino M. (1995): SAEG
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Page 158 and 159: References Traquilla, J. M. and J.
Page 160 and 161: Acknowledgments 152
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Precise Orbit Determination of Global Navigation Satellite System of ...

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