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

Chapter 8 Geostationary Orbit Determination And Prediction During Satellite Maneuvers
Difference (meter)
30
20
10
0
-10
-20
Maneuver Start
-30
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
Time (hour)
Maneuver Stop
Figure 8-9 Dynamic Orbit Determination of Geostationary Satellite during Maneuver
Comparing Figure 8-5 with Figure 8-8, it shows that there are no great differences found for orbit determination
using kinematic method with or without maneuver operations. This property can be used for improving
maneuver force model. Comparing Figure 8-6 with Figure 8-9 it is obvious that during satellite maneuver, the
accuracy of the dynamic orbit determination is significantly degraded. For some larger maneuver force, the
accuracy of dynamic orbit determination would be worse. This is because in the dynamic method, no precise
maneuver force models are included. Even if the maneuver force models were included, but there were some
unmodeled or mismodeled errors, the accuracy of the dynamic orbit determination would also be reduced.
8.3 Maneuver Force Model
For post-processing, it is sufficient to use the kinematic method for orbit determination during satellite
maneuver. For real-time navigation application, users usually need the so-called satellite ephemeris, i.e.
predicted orbit, as a reference to compute their positions and velocities. The kinematic method can be used to
determine the satellite orbit during satellite maneuver, but it cannot be used to predict orbit. For orbit prediction,
the dynamic method is still needed and the maneuver force should be included in the satellite dynamic force
models.
First let us see the accuracy of orbit prediction using current dynamic models without satellite maneuver force
model included.
Figure 8-10 and Figure 8-11 show the accuracy of orbit prediction due to the maneuver accelerations expressed
by Eq.(8-53). The maneuver operation lasts about 5 hours. Figure 8-12 shows the accuracy of orbit prediction
due to the maneuver accelerations written below and the maneuver operation lasts about 48 minutes
−5
2
x&= y& = 8× 10 m/ s �
�
z&=
0
�
107
dx
dy
dz
(8-54)