Galileo Architecture: Difference between revisions

Latest revision as of 07:19, 14 December 2020

The Galileo System is an independent, global, European-controlled, satellite-based navigation system and will provide a number of guaranteed services to users equipped with Galileo-compatible receivers once it achieves its Full Operational Capability foreseen for 2020. From 2016, Galileo moved from a testing phase to the provision of life services thanks to the Galileo Initial Services declaration.

To ensure GALILEO services, a specific architecture is deployed, that consists of 30 satellites, to be deployed in a staggered approach, and the associated ground infrastructure.^[1] The Galileo system is divided into three major segments: Space Segment, Ground Segment and User Segment.

Introduction

Galileo Architecture

The Galileo infrastructure is composed of:

a constellation of 30 satellites (including 6 spares) in Medium-Earth Orbit (MEO). Each satellite contains a navigation payload and a search and rescue transponder;
a global network of Galileo Sensor Stations (GSS) providing coverage for clock synchronisation and orbit measurements;
two Control Centres;
a network of Mission Uplink stations;
Telemetry, Tracking and Control (TT&C) stations.
additional core infrastructure to service which support the provision of the Galileo service.

This infrastructure is organized in two segments, the Space Segment and the Ground Segment, to be complemented by the user receivers, which compose the User Segment.

GALILEO Space Segment

Galileo Space Segment

The main functions of the Galileo Space Segment are to generate and transmit code and carrier phase signals with a specific Galileo signal structure, and to store and retransmit the navigation message sent by the Control Segment. These transmissions are controlled by highly stable atomic clocks on board the satellites.

When Galileo is fully operational, there will be 30 satellites in Medium Earth Orbit (MEO) at an altitude of 23,222 kilometres. The satellites will occupy each of three orbital planes inclined at an angle of 56° with respect to the equator. The satellites will be spread evenly around each plane and will take about 14 hours to orbit the Earth. Each orbital plane includes 8 satellites uniformly distributed within the plane. The angular shift between satellites in two adjacent planes is 15º. One satellite in each plane will be a spare, on stand-by should any operational satellite fail. The full constellation includes 6 spare satellites, resulting a walker 24/3/1 constellation. These spare satellites can be activated and allocated to a given operational slot depending on maintenance or service evolution activities. The constellation geometry repetition period corresponding to the nominal orbital parameters is 10 days (corresponding to 17 orbital revolutions). This means that for any fixed Galileo user, the local satellite geometry at a given instant is repeated every 10 sideral days. In the following table are shown the Nominal Value of the different Reference Orbit Parameters:

*Galileo Reference Orbit Parameters*
Reference Orbit Parameter	Nominal Value
Orbit semi-major axis, m	29599801
Orbit eccentricity	1E-07
Orbit inclination, deg	56.0
Argument of Perigee, deg	0.0

Highly accurate atomic clocks are installed on these satellites. Each of the 30 satellites in the Galileo system has two of each type of clock on board, a rubidium and a hydrogen maser clock. The frequency is at around 6 GHz for the rubidium clock and at around 1.4 GHz for the hydrogen clock. The Galileo system uses the clock frequency as a very stable reference by which other units can generate the accurate signals that the Galileo satellites will broadcast. The broadcast signals also provide a reference by which the less stable user receiver clocks can continuously reset their time.

The satellites are deployed gradually according to the Galileo Program schedule.

GALILEO Ground Segment

The Galileo Ground Segment is the responsible for the proper operation of the GNSS system. It comprises two control centres, a global network of transmitting and receiving stations implementing monitoring and control functions and a series of service facilities which support the provision of the Galileo services^[1].

The core of the GALILEO ground segment are the two Galileo Control Centres (GCC). Each control centre manages control functions supported by a Galileo Control Segment (GCS) and mission functions, supported by a dedicated Galileo Mission Segment (GMS). The GCS handles spacecraft housekeeping and constellation maintenance while the GMS handles navigation system control. The GCS and GMS interfaces the satellites with a worldwide ground station network implementing control and monitoring functions^[1]^[2].

The Galileo Control Segment (GCS) is responsible for a large range of functions to support satellite constellation control and management of Galileo satellites. The scope of this functionality includes control and monitoring of the satellites and payload, planning and automation functions that allow safe and correct operations to take place, and the support of payload related operations by means of Telemetry Tracking and Control (TT&C) stations links. The GCS provides the telemetry, telecommand and control function for the whole Galileo satellite constellation. Its functional elements are deployed within the Galileo Control Centres (GCC) and the six globally distributed Telemetry Tracking and Control (TT&C) stations. To manage this, the GCS uses the TT&C stations to communicate with each satellite on a scheme combining regular, scheduled contacts, long-term test campaigns and contingency contacts.

The Galileo Mission Segment (GMS) consists of facilities deployed in the two Galileo Control Centres (GCCs) plus a series of Mission Up-Link Stations (ULS) and Galileo Sensor Stations (GSS) deployed at remote sites located around the world. The GMS is responsible for the determination and uplink of navigation data messages needed to provide the navigation and timing data. For this purpose, it uses a global network of Galileo Sensor Stations (GSS)^[1]^[2] to monitor the navigation signals of all satellites on a continuous basis, through a comprehensive communications network using commercial satellites as well as cable connections in which each link is duplicated for redundancy.

GALILEO User Segment

The Galileo User Segment is composed by Galileo receivers. Their main function is to receive Galileo signals, determine pseudoranges (and other observables), and solve the navigation equations in order to obtain their coordinates and provide a very accurate time.

Notes

References

GALILEO
Title	Galileo Architecture
Edited by	GMV
Level	Basic
Year of Publication	2011

[Galileo-OS-SDD-1] Galileo Open Service - Service Definition Document

[Galileo_System-2] Galileo System at European Galileo Service Centre website

[1]

[2]

@@ Line 1: / Line 1: @@
-{{Article Infobox2
-|Category=GALILEO
-|Title={{PAGENAME}}
-|Authors=GMV
-|Level=Basic
-|YearOfPublication=2011
-|Logo=GMV
-}}
-The Galileo is a space-based global navigation satellite system (GNSS) that provides reliable positioning, navigation, and timing services to users on a continuous worldwide basis freely available to all. Galileo receivers compute their position in the [[Galileo Reference Frame|Galileo Reference System]] using satellite technology and based on [[An intuitive approach to the GNSS positioning|triangulation principles]].
+The [[GALILEO General Introduction|Galileo]] System is an independent, global, European-controlled, satellite-based navigation system and will provide a number of guaranteed services to users equipped with Galileo-compatible receivers once it achieves its Full Operational Capability foreseen for 2020. From 2016, Galileo moved from a testing phase to the provision of life services thanks to the Galileo Initial Services declaration.
+To ensure GALILEO services, a specific architecture is deployed, that consists of 30 satellites, to be deployed in a staggered approach, and the associated ground infrastructure.<ref name="Galileo-OS-SDD">[https://www.gsc-europa.eu/system/files/galileo_documents/Galileo-OS-SDD.pdf Galileo Open Service - Service Definition Document]</ref> The Galileo system is divided into three major segments: [[GALILEO Space Segment|Space Segment]], [[GALILEO Ground Segment|Ground Segment]] and [[GALILEO User Segment|User Segment]].
 ==Introduction==
+[[File:GalileoFOCArchitecture.JPG|300px|Galileo Architecture|thumb]]
-The Galileo program is Europe's initiative for a state-of-the-art global satellite navigation system, providing a highly accurate, guaranteed global positioning service under civilian control.<ref name="CR Galileo">Council Resolution of 19 July 1999 on the involvement of Europe in a new generation of satellite navigation services -Galileo- Definition phase [http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:C:1999:221:0001:0003:EN:PDF (1999/C 221/01)]</ref> While providing autonomous navigation and positioning services, the system established under the Galileo program will at the same time be interoperable with other GNSS systems such as [[GPS]] and [[GLONASS]]. The system will consist of 30 satellites, to be deployed in a staggered approach, and the associated ground infrastructure.<ref>[http://www.esa.int/esaNA/galileo.html ESA Galileo web page]</ref>
+The Galileo infrastructure is composed of:
+* a constellation of 30 satellites (including 6 spares) in Medium-Earth Orbit (MEO). Each satellite contains a navigation payload and a search and rescue transponder;
-A user will be able to take a position with the same receiver from any of the satellites in any combination. By offering dual frequencies as standard, Galileo will deliver real-time positioning accuracy down to the meter range.  It will guarantee availability of the service under all but the most extreme circumstances and will inform users within seconds of a failure of any satellite. This will make it suitable for applications where safety is crucial, such as running trains, guiding cars and landing aircraft.
+* a global network of Galileo Sensor Stations (GSS) providing coverage for clock synchronisation and orbit measurements;
+* two Control Centres;
-The first experimental satellites, GIOVE-A (launched on 2005) and GIOVE-B (launched on 2008) have already tested critical technologies and secured the Galileo frequencies within the [[Wikipedia:International Telecommunications Union|International Telecommunications Union]]. Thereafter, four operational satellites - the basic minimum for satellite navigation in principle - will be launched in 2011 to validate the Galileo concept with both segments: space and related ground infrastructure.
+* a network of Mission Uplink stations;
+* Telemetry, Tracking and Control (TT&C) stations.
-Based on the award of the contracts for the first order of satellites, the launch services, the system support services and the operations, the [[Wikipedia:European Commission|European Commission]] announced the Initial Operational Capability (IOC) with three initial services to be provided in 2014/2015: an initial [[GALILEO Open Service|Open Service]], an initial [[GALILEO Public Regulated Service|Public Regulated Service]] and an initial [[GALILEO Search and Rescue Service|Search and Rescue Service]].<ref>Commission awards major contracts to make Galileo operational early 2014,  [http://europa.eu/rapid/pressReleasesAction.do?reference=IP/10/7 IP/10/7], Brussels, 7 January 2010.</ref> At this stage, accuracy and availability will not yet have reached their optimum level, the [[GALILEO Safety-of-Life Service|Safety-of-Life Service]] and the [[GALILEO Commercial Service| Commercial Service]] will be tested and will be provided as the system reaches full operational capability with the 30 satellites<ref name="Mid-term review">[http://ec.europa.eu/enterprise/newsroom/cf/_getdocument.cfm?doc_id=6321 Mid-term review of the European satellite radio navigation programmes]</ref>
+* additional core infrastructure to service which support the provision of the Galileo service.
-Galileo will ensure Europe's independence in a sector that has become critical for its economy and the well-being of its citizens.
-[[GPS]] (US), [[GLONASS]] (Russia) and the other regional systems developed by Japan and China are military systems under military control – indeed they provide a civil service but that civil service could be either switched off or made less precise when desired e.g. in case of conflict. The world has become so dependent on services provided by satellite navigation in our daily lives that should a service be reduced or switched off, the potential disruption to business, banking, transport, aviation, communication, etc., to name but a few, would be very costly (e.g. in terms of revenues for business, road safety, etc.).
-The combination of Galileo and [[GPS]] signals ([[Principlies of Interoperability amongs GNSS|inter-operability]]) in dual receivers will open the door to new [[GNSS Application|GNSS applications]] that require a higher level of precision than currently available with [[GPS]] alone. From most locations, six to eight Galileo satellites will be visible which, in combination with [[GPS]] signals, will allow positions to be determined up to within a few centimetres. Examples of these applications are: guide the blind, increase the success rate of rescue operations in the mountains, monitor the whereabouts of people suffering from Alzheimer Disease, etc.
+This infrastructure is organized in two segments, the [[GALILEO Space Segment|Space Segment]] and the [[GALILEO Ground Segment|Ground Segment]], to be complemented by the user receivers, which compose the [[GALILEO User Segment|User Segment]].
-In addition, Galileo will improve the overall [[Availability|availability]] and coverage of GNSS signals. For example, the higher number of satellites will improve the [[Availability|availability]] of the signals in high rise cities where buildings can obstruct signals from satellites that are low on the horizon.
+==GALILEO Space Segment==
+[[File:Galileo Space Segment.jpg|250px|Galileo Space Segment|left|thumb]]
+The main functions of the [[GALILEO Space Segment|Galileo Space Segment]] are to generate and transmit code and carrier phase signals with a specific [[GALILEO Signal Plan|Galileo signal structure]], and to store and retransmit the navigation message sent by the [[GALILEO Ground Segment|Control Segment]]. These transmissions are controlled by highly stable atomic clocks on board the satellites.
-With Galileo, Europe will be able to exploit the opportunities provided by satellite navigation to the full extent. [[GNSS Receivers|GNSS receiver]] and equipment manufacturers, application providers and service operators will benefit from novel business opportunities.<ref name="EC GAL web">[http://ec.europa.eu/enterprise/policies/satnav/galileo/index_en.htm EC Galileo website]</ref>
+When Galileo is fully operational, there will be 30 satellites in Medium Earth Orbit (MEO) at an altitude of 23,222 kilometres. The satellites will occupy each of three orbital planes inclined at an angle of 56° with respect to the equator. The satellites will be spread evenly around each plane and will take about 14 hours to orbit the Earth. Each orbital plane includes 8 satellites uniformly distributed within the plane. The angular shift between satellites in two adjacent planes is 15º.
+One satellite in each plane will be a spare, on stand-by should any operational satellite fail. The full constellation includes 6 spare satellites, resulting a walker 24/3/1 constellation. These spare satellites can be activated and allocated to a given operational slot depending on maintenance or service evolution activities.
+The constellation geometry repetition period corresponding to the nominal orbital parameters is 10 days (corresponding to 17 orbital revolutions). This means that for any fixed Galileo user, the local satellite geometry at a given instant is repeated every 10 sideral days.
+In the following table are shown the Nominal Value of the different Reference Orbit Parameters:
-==History and Development==
+{| class="wikitable" align="center"
+|+align="bottom" |''Galileo Reference Orbit Parameters''
+|-
+! Reference Orbit Parameter
+! Nominal Value
+|- align="center"
+| Orbit semi-major axis, m
+| 29599801
+|- align="center"
+| Orbit eccentricity
+| 1E-07
+|- align="center"
+| Orbit inclination, deg
+|  56.0
+|- align="center"
+| Argument of Perigee, deg
+| 0.0
+|- align="center"
+|}
-As far back as the 1990s, the [[Wikipedia:European Union|European Union]] saw the need for Europe to have its own global satellite navigation system.<ref name="CR Galileo"/> The conclusion to build one was taken in similar spirit to decisions in the 1970s to embark on other well-known European endeavours, such as the [http://www.esa.int/esaMI/Launchers_Home/index.html Ariane] launcher and the [[Wikipedia:Airbus|Airbus]]. The [[Wikipedia:European Commission|European Commission]] and [http://www.esa.int/ European Space Agency] joined forces to build Galileo, an independent European system under civilian control.
-The definition phase and the development and In-Orbit Validation phase of the Galileo program were carried out by the [http://www.esa.int/ European Space Agency (ESA)] and co-funded by ESA and the [[Wikipedia:European Union|European Union]]. The Full Operational Capability phase of the Galileo program is fully funded by the [[Wikipedia:European Union|European Union]] and managed by the [[Wikipedia:European Commission|European Commission]]. The [[Wikipedia:European Commission|Commission]] and [http://www.esa.int/ ESA] have signed a delegation agreement by which [http://www.esa.int/ ESA] acts as design and procurement agent on behalf of the [[Wikipedia:European Commission|Commission]].
+Highly accurate atomic clocks are installed on these satellites. Each of the 30 satellites in the Galileo system has two of each type of clock on board, a rubidium and a hydrogen maser clock. The frequency is at around 6 GHz for the rubidium clock and at around 1.4 GHz for the hydrogen clock. The Galileo system uses the clock frequency as a very stable reference by which other units can generate the accurate signals that the Galileo satellites will broadcast. The broadcast signals also provide a reference by which the less stable user receiver clocks can continuously reset their time.
-The Galileo program has been structured according to three main phases:<ref name="EC GAL web"/>
+The satellites are deployed gradually according to the [[GALILEO_Future_and_Evolutions|Galileo Program schedule]].
-* In-Orbit Validation (IOV) phase:
-:The IOV phase consists of qualifying the system through tests and the operation of two experimental satellites and a reduced constellation of four operational satellites and their related ground infrastructure.
-:The two experimental satellites were launched in respectively December 2005 and April 2008. Their purpose was to characterize the Medium-Earth Orbit (MEO) environment (radiations, magnetic field etc) and to test in such environment the performance of critical payload technology (atomic clocks and radiation hardened digital technology). They also provide an early experimental signal-in-space allowing securing the frequency spectrum required for Galileo in accordance with WRC RNSS allocations. The launch of the first two operational satellites is scheduled for end of 2011.
-* Initial Operational Capability (IOC) phase:
+==GALILEO Ground Segment==
-:The IOC stage will be the partial commissioning of the ground and space infrastructure as from 2014-2015 and the provision of the [[GALILEO Open Service|open service]], the [[GALILEO Search and Rescue Service|search and rescue service]] and the [[GALILEO Public Regulated Service|PRS]]. While this first stage will be sufficient to test the services it should nonetheless be as short as possible, because it will not allow the system's full potential to be exploited and will not meet the requirements of all users.
+The [[GALILEO Ground Segment|Galileo Ground Segment]]  is the responsible for the proper operation of the GNSS system. It comprises two control centres, a global network of transmitting and receiving stations implementing monitoring and control functions and a series of service facilities which support the provision of the Galileo services<ref name="Galileo-OS-SDD"></ref>.
-* Full Operational Capability (FOC) phase:
-:The FOC phase consists of the deployment of the full system which will consist of 30 satellites, control centres located in Europe and a network of sensor stations and uplink stations installed around the globe. Galileo's Full Operational Capability (FOC) should be achieved in 2019-2020, in a staggered approach from the IOC phase. It might change, depending on availability of financing, technical problems and industrial performance.
-==[[GALILEO Architecture]]==
+The core of the GALILEO ground segment are the two Galileo Control Centres (GCC). Each control centre manages ''control'' functions supported by a '''Galileo Control Segment (GCS)''' and ''mission'' functions, supported by a dedicated '''Galileo Mission Segment (GMS)'''. The GCS handles spacecraft housekeeping and constellation maintenance while the GMS handles navigation system control. The GCS and GMS interfaces the satellites with a worldwide ground station network implementing control and monitoring functions<ref name="Galileo-OS-SDD"/><ref name="Galileo_System">[https://www.gsc-europa.eu/galileo/system Galileo System at European Galileo Service Centre website]</ref>.
-[[File:Galileo Space Segment.jpg|250px|Galileo Space Segment|right|thumb]]To ensure these Galileo services, a specific architecture is deployed.  The Galileo system is divided into three major segments: [[GALILEO Space Segment|Space Segment]], [[GALILEO Ground Segment|Control Segment]] and [[GALILEO User Segment|User Segment]]. For details see [[GALILEO Architecture|Galileo Architecture]].
+The '''Galileo Control Segment (GCS)''' is responsible for a large range of functions to support satellite constellation control and management of Galileo satellites. The scope of this functionality includes control and monitoring of the satellites and payload, planning and automation functions that allow safe and correct operations to take place, and the support of payload related operations by means of Telemetry Tracking and Control (TT&C) stations links. The GCS provides the telemetry, telecommand and control function for the whole Galileo satellite constellation. Its functional elements are deployed within the Galileo Control Centres (GCC) and the six globally distributed Telemetry Tracking and Control (TT&C) stations. To manage this, the GCS uses the TT&C stations to communicate with each satellite on a scheme combining regular, scheduled contacts, long-term test campaigns and contingency contacts.
-The main functions of the [[GALILEO Space Segment|Galileo Space Segment]] are to generate and transmit code and carrier phase signals with a specific [[GALILEO Signal Structure|Galileo signal structure]], and to store and retransmit the navigation message sent by the [[GALILEO Ground Segment|Control Segment]]. These transmissions are controlled by highly stable atomic clocks on board the satellites.
+The '''Galileo Mission Segment (GMS)''' consists of facilities deployed in the two Galileo Control Centres (GCCs) plus a series of Mission Up-Link Stations (ULS) and Galileo Sensor Stations (GSS) deployed at remote sites located around the world. The GMS is responsible for the determination and uplink of navigation data messages needed to provide the navigation and timing data. For this purpose, it uses a global network of Galileo Sensor Stations (GSS)<ref name="Galileo-OS-SDD"/><ref name="Galileo_System"/> to monitor the navigation signals of all satellites on a continuous basis, through a comprehensive communications network using commercial satellites as well as cable connections in which each link is duplicated for redundancy.
-When Galileo is fully operational, there will be 30 satellites in Medium Earth Orbit (MEO) at an altitude of 23,222 kilometres. The satellites will occupy each of three orbital planes inclined at an angle of 56° to the equator. The satellites will be spread evenly around each plane and will take about 14 hours to orbit the Earth. One satellite in each plane will be a spare; on stand-by should any operational satellite fail.
+==GALILEO User Segment==
+The  [[GALILEO User Segment|Galileo User Segment]] is composed by [[GALILEO Receivers|Galileo receivers]]. Their main function is to receive Galileo signals, determine pseudoranges (and other observables), and solve the navigation equations in order to obtain their coordinates and provide a very accurate time.
-[[File:Galileo Ground Segment.png|300px|Galileo Ground Segment|left|thumb]]The [[GALILEO Ground Segment|Galileo Control Segment]] (also referred to as Ground Segment) is the responsible for the proper operation of the GNSS system. Its basic functions are:
-* To control and maintain the status and configuration of the satellite constellation.
-* To predict ephemeris and satellite clock evolution.
-* To keep the corresponding GNSS time scale (through atomic clocks).
-* To update the navigation messages for all the satellites.
-The [[GALILEO Ground Segment|Galileo Ground Segment]] constitutes the major system element controlling the entire constellation, the navigation system facilities and the dissemination services. It is composed of two Ground Control Centres (GCC), five Telemetry, Tracking and Control (TT&C) stations, nine Mission Uplink Stations (ULS), and about fourteen Galileo Sensor Stations (GSS).
-The  [[GALILEO User Segment|Galileo user segment]] is composed by [[GALILEO Receivers|Galileo receivers]]. Their main function is to receive Galileo signals, determine pseudoranges (and other observables), and solve the navigation equations
-in order to obtain their coordinates and provide a very accurate time.
 ==Notes==
 <references group="footnotes"/>
 ==References==
-<references/>
+<references/>{{Article Infobox2
+|Category=GALILEO
+|Editors=GMV
+|Level=Basic
+|YearOfPublication=2011
+|Logo=GMV
+|Title={{PAGENAME}}
+}}
-[[Category:GALILEO]]
+[[Category:GALILEO|Architecture]]
+[[Category:GALILEO Architecture]]
+[[Category:GALILEO Ground Segment]]