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

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Chapter 6 Algorithms of Orbit Determination of IGSO, GEO and MEO Satellites 84
Chapter 7 Orbit Determination Using Carrier Phase Observation CHAPTER 7 ORBIT DETERMINATION USING CARRIER PHASE OBSERVATIONS Highly precise orbit determination of IGSO, GEO and MEO satellites is a key issue for second generation of Global Navigation Satellite System (GNSS-2). According to research work (Hein et al, 1997), using pseudorange observation the accuracy of orbit determination of IGSO and GEO satellites is about 1-2 meters. In order to obtain better accuracy of satellite orbits, one should use the carrier phase measurements that are the most accurate observations available at present. The carrier phase observable is biased by integer number of cycles called an initial ambiguity. If the initial ambiguities of carrier phase observations are solved, precise orbit determination with the accuracy of order of better than 1 meter level can be achieved. In this chapter, the orbit determination of IGSO, GEO and MEO satellites using carrier phase observations are described. Some problems of carrier phase observations with IGSO, GEO and MEO orbit determination are presented. The initial ambiguity resolution which could be used for orbit determination are discussed. In order to overcome the influence of multipath effects on initial ambiguity resolution, a new and unique method for reduction of multipath effects is presented and discussed. The results of orbit determination using carrier phase observations based on simulation data are shown in §9.3, Chapter 9. The cycle slip problem in the carrier phase observations is not considered. 7.1 Mathematical Models for Carrier Phase Observations 7.1.1 Carrier Phase Orbit determination using carrier-phase observations is greatly different from that using range observations. Carrier phase observations are biased by integer number of cycles and oscillator frequency offsets between the transmitter and the receiver. In the observation equations, the initial ambiguities should be included as parameters and resolved with other parameters at the same time. From Eq.(2-43), Chapter 2, the carrier phase observation equation is rewritten as 2π L = ϕ r() t − ϕt() t = S1 + λN1 + ε (7-1) λ where ϕ r 1 ϕ t receiver’s phase, received satellite phase at the nominal reception time t , N1 initial integer ambiguity, λ1 wavelength of signal frequency c speed of light in vacuum, ε carrier-phase measurement noise including hardware delays of receiver and the satellite as well as multipath. S1 line-of-sight between satellite and tracking station 7.1.2 Doppler Doppler measurements may also be used to determine the satellite orbit. The basic observation equation of integrated Doppler count measurement is given by (Figure 2-3) L = ( f − f )( t f0 − t ) + ( S −S ) where f0 ft 0 t 3 1 c 2 1 (7-2) the reference frequency of the receiver the transmitting frequency of satellite signal (not shifted by Doppler effect) S1, S2 line-of-sights between satellite and tracking station at different epochs 85
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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 9 Software and Simulation R
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Conclusion 144
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References Carpino M. (1995): SAEG
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References Klobuchar, J. A.(1996):
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References Traquilla, J. M. and J.
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Acknowledgments 152
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