Projects:
Definition
& Development
of Galileo
Signal Structure
Galileo Test
Bed GATE
ESA Galileo
Test Bed GSTB_V1
GNSS Software
Simulation
C-Nav
Study |
Definition and Development of Galileo
The Institute of Geodesy and Navigation contributes to the definition,
development and validation phase of the European Galileo system by providing
input the signal task force of the European Community (EC).The Galileo project
is carried out in co-operation by bodies EC and the European Space Agency
(ESA). In principle it is to be realised in three phases: project definition,
development and implementation. The fundamental decision for the realization
Galileo was made by the council of the European ministers of transport at
March 26, 2002. According to the present planning the development and validation
phase should cover the period 2005-2009, the implementation phase 2009-2012,
and the operational phase could start in 2013.
Overall Architecture
The main characteristics of the Galileo system architecture can be summarised
as follows
• Independence of other satellite navigation systems
• Interoperability with GPS (GLONASS)
• Service concept (open, commercial, safety critical, regulated)
• Implementation of an Integrity Service (inside/outside Europe)
• Independence between Integrity Service and Galileo control System
(GCS)
• Global services (SAR, and referred to navigation data related
services)
• Global location and time dissemination on the basis of a global
constellation
• Regional components (Monitor and uplink stations)
• Integration with regional systems (e.g. EGNOS)
• Integration with local (differential etc.) systems
• Compatibility with future mobile radio networks
(UMTS)
The main
extension of Galileo compared to GPS consists in the implementation of a
global/ regional segment for integrity monitoring. The goal is to assist
the safety critical aircraft navigation (landing approach CAT I) and to locate
and guide railway trains (Train control).
Space Segment
The space
segment of Galileo is intended to consist of a total 30 Mean Earth Orbiting
(MEO) satellites configured as walker 27/3/1 (+ 3 replacement satellites)
constellation (Benedicto et al., 2000), i.e. distributed over three orbital
planes. The altitude is 23616 km, and the inclination is 56°. The satellite
design is based on already carried out precursor programs (e.g. GLOBALSTAR)
including critical payload technologies, which are developed in accompanying
ESA programs. The Galileo satellite has a mass of 625 kg, generates a primary
power of 1500 W and belongs with dimensions of 2.7 x 1.2 x 1.1 m3;
to the category mini-satellites. The satellite comprises all standard systems
for orbit and attitude control, thermal control, etc. Unlike GPS, also Laser
retro-reflectors will be integrated in order to assist the orbit determination
by satellite Laser ranging.
The navigation payload is the heart of the Galileo satellite. The payload
is a regenerative transponder with modern digital and semiconductor technology
applied to the essential subsystems. It consists of atomic clocks (Clock
Monitoring and Control Unit), the signal generator (Navigation Signal Generation
Unit) with CPU, the frequency generator (FPGU), the output amplifier (Solid
State Power Amplifier) and the L-band antenna sub-system. As atomic clocks
two Rubidium standards (5 10 -13 over 100 s) and two space-borne H-Masers
(5 10 -14 over 10000 s) are to be used.
Ground Segment
As already
outlined, the Galileo ground segment comprises the control segment for operation
as well as orbit and time determination (GCS or Ground Control Segment) and
the system for integrity monitoring (IDS or Integrity Determination
System).The number of elements in the GCS and the IDS are under further
investigation in the present definition phase. The GCS will consist of about
12-15 reference stations, 5 up-link stations and two control centres. The
IDS for Europe will include 16-20 monitor stations, three up-link stations
for integrity data and two central stations for integrity computations. In
the European area the integration with the EGNOS ground segment plays an
important role.
Point
of contact: Thomas Pany |
