Orbit determination strategy using single frequency GPS data

다국어 초록 (Multilingual Abstract)

This thesis presents an orbit solution determined by various ionospheric error correction schemes for LEO (Low Earth Orbit) satellites carrying single frequency GPS receiver. A scale factor, dependent on satellite altitude, was applied to the model-based ionosphere correction method. The direct-calibration method, DRVID (Differenced Range Versus Integrated Doppler), used the difference of group delay and phase advance to correct for the first order ionospheric error. The ionospheric error was corrected using an assumption of zero-bias at the minimum range epoch. This assumption introduces some orbit error. The disadvantage of the zero-bias assumption was overcome by estimating measurement bias during the orbit determination process.
The fidelity of the ionospheric error correction methods was demonstrated by evaluating the orbit accuracy using the CHAMP (Challenging Mini-satellite Payload) satellite. The orbit accuracy study for the LEO satellite was completed using the MicroCosm software. The conventional dynamic orbit solution method estimated position, velocity, empirical accelerations along the cross-track and along-track directions, a drag coefficient, and a solar pressure coefficient.
The orbit overlap differences, calculation of the orbit difference from dual frequency truth orbits, and comparison with JPL (Jet Propulsion Laboratory)'s POD (Precise Orbit Determination) were used as methods for evaluating orbit accuracy. The orbit overlap solution resulted in a level of several tens of centimeters RSS in a 3-D sense if the ionospheric error was corrected. The orbit, estimated by the DRVID carrier phase data, differed by 40 centimeters RSS from the truth orbit. However, the orbit determined without any ionospheric error correction showed 2.4 meters RSS in a 3-D sense in comparison to the truth orbit. The orbits compared to the JPL's POD solution over four days appeared to be less than 1 meter RSS difference in a 3-D sense for both the ionosphere-free orbit and the orbit using DRVID carrier phase data.
The analyses showed that the DRVID ionospheric error correction method can determine the orbit accuracy below the meter level with a single frequency receiver on the LEO satellite.

목차 (Table of Contents)

• ACKNOWLEDGEMENTS = v
• CONTENTS = vi
• TABLES = viii
• FIGURES = x
• CHAPTER 1 INTRODUCTION = 1
• 1.1 Purpose of Research = 2
• 1.2 GPS Overview = 5
• 1.3 Previous Research = 6
• 1.4 CHAMP Satellite Mission = 7
• 1.5 MicroCosm = 8
• 1.6 Outline = 9
• CHAPTER 2 ORBIT SYSTEM = 11
• 2.1 Time and Coordinate System = 11
• 2.2 Force Model = 12
• 2.2.1 Gravity Field = 13
• 2.2.2 Atmospheric Drag = 14
• 2.2.3. Solar Radiation Pressure = 16
• 2.3 Empirical Acceleration = 19
• 2.4 GPS Ground Networks = 20
• 2.5 GPS Measurements = 21
• 2.5.1 Double Differenced Measurements = 23
• 2.5.2 GPS Measurement Error = 24
• 2.6 Orbit Estimation Strategy = 25
• CHAPTER 3 IONOSPHERE ERROR ANALYSIS = 29
• 3.1 Ionosphere Error = 29
• 3.1.1 Dual Frequency Ionospheric Error Correction = 31
• 3.1.2 Differential Range Versus Integrated Doppler (DRVID) = 33
• 3.1.3 Ionosphere Model = 35
• 3.1.3.1 JPL's GIM = 37
• 3.1.3.2 CODE's GIM = 40
• 3.1.3.3 IRI Model = 41
• 3.2 Ionosphere Model Data Processing = 42
• 3.3 Scale Factor for the LEO Satellite Ionospheric Error Correction = 46
• 3.4 Ionosphere Error Analysis = 49
• 3.5 Differential Code Bias (DCB) = 55
• CHAPTER 4 ORBIT SOLUTION COMPARISON = 59
• 4.1 Dynamic Orbit System = 59
• 4.2 Orbit Solution Assessment = 62
• 4.2.1 Postfit Residual = 62
• 4.2.2 Orbit Overlap Solutions = 71
• 4.2.2.1 Comparison of Pseudorange Orbit Overlaps = 72
• 4.2.2.2 Comparison of Carrier Phase Orbit Overlaps = 77
• 4.2.3 Internal Orbit Differences = 82
• 4.2.4 Comparison of GIPSY/OASIS H and MicroCosm Solutions = 89
• CHAPTER 5 ORBIT PREDICTION = 99
• 5.1 Introduction = 99
• 5.2 Results = 102
• CHAPTER 6 CONCLUSIONS = 118
• 6.1 Summary = 118
• 6.2 Conclusions = 120
• 6.3 Future Research = 121
• BIBLIOGRAPHY = 123