Viavi 87339, Operation Manual

Page: 145 / 198

Principals of Operation
6 -28
6.1.9 The Galileo System
Galileo is the European global navigation satellite system which provides a highly
accurate, guaranteed global positioning service under civilian control. It is inter-operable
with GPS and GLONASS, the two other global satellite navigation systems.
Fig. 6-28 Galileo Satellite (GIOVE Test SV)
A user can take a position with the same receiver from any of the satellites in any
combination. By offering dual frequencies as standard, Galileo delivers real-time
positioning accuracy down to the meter range. Galileo guarantees availability of the
service under all but the most extreme circumstances and informs users within seconds
of a failure of any satellite. This makes it suitable for applications where safety is crucial,
such as running trains, guiding cars and landing aircraft.
The first experimental satellite, part of the so-called Galileo System Test Bed (GSTB-V1),
was launched in 2003. The objective of this satellite was to characterize the critical
technologies, developed under ESA contracts. Two initial test satellites were launched
GIOVE-A, in 2005, and GIOVE-B, in 2008, to validate the basic Galileo space segment.
Four In Orbit Validation (IOV) satellites are scheduled to be launched in the 2010 to 2011
time frame, to complete the validation of the space segment in conjunction with the
ground segment. A further 16 satellites are currently funded, which will provide a
minimum operational capability. The balance of 14 satellites required to reach Full
Operational Capability (FOC), as of 2010, are not currently funded.
The fully deployed Galileo system will consist of 30 satellites (27 opera 3 active
spares), positioned in three circular Medium Earth Orbit (MEO) planes at 23 222 km
altitude above the Earth, and at an inclination of the orbital planes of 56 degrees with
reference to the equatorial plane. The Galileo navigation signals provide good coverage
even at latitudes up to 75 degrees north, which corresponds to the North Cape, and
beyond.
The large number of satellites together with the optimization of the constellation, and the
availability of the three active spare satellites, ensures that the loss of one satellite has
no discernible effect on the user. The use of BOC (Binary Offset Carrier) Modulation
minimizes interference with GPS BPSK.