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

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
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