Galileo Space Segment - Revision history

Gema.Cueto: Updated reference ICD/SDD links

2026-04-17T11:33:08Z

Updated reference ICD/SDD links

← Older revision		Revision as of 11:33, 17 April 2026
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	[[File:Galileo satellite system.jpg\|right\|thumb\|300px\|Galileo satellite]]		[[File:Galileo satellite system.jpg\|right\|thumb\|300px\|Galileo satellite]]

	The Galileo constellation is composed of a total of 30 Medium Earth Orbit (MEO) satellites, of which 6 are spares. Each satellite broadcasts precise time signals, ephemeris and other data. The Galileo satellite constellation has been optimised to the following nominal constellation specifications:<ref name="OS SDD"> [https://www.gsc-europa.eu/sites/default/files/sites/all/files/Galileo-OS-~~SDD_v1.1~~.pdf Applicable galileo Open Service (OS) Service Definition Document (SDD)]</ref>		The Galileo constellation is composed of a total of 30 Medium Earth Orbit (MEO) satellites, of which 6 are spares. Each satellite broadcasts precise time signals, ephemeris and other data. The Galileo satellite constellation has been optimised to the following nominal constellation specifications:<ref name="OS SDD"> [https://www.gsc-europa.eu/sites/default/files/sites/all/files/Galileo-OS-SDD_in_force.pdf Applicable galileo Open Service (OS) Service Definition Document (SDD)]</ref>

	*circular orbits (satellite altitude of 23 222 km)		*circular orbits (satellite altitude of 23 222 km)
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	*six spare satellites (also transmitting)		*six spare satellites (also transmitting)

	The constellation is complemented by spare satellites that can be repositioned to any given slot depending on maintenance or service evolution needs. The location of the spare satellites in each plane is not yet frozen and will be decided at the time of deployment of the spare capability.<ref name="OS SDD"> [https://www.gsc-europa.eu/sites/default/files/sites/all/files/Galileo-OS-~~SDD_v1.1~~.pdf Applicable galileo Open Service (OS) Service Definition Document (SDD)]</ref>		The constellation is complemented by spare satellites that can be repositioned to any given slot depending on maintenance or service evolution needs. The location of the spare satellites in each plane is not yet frozen and will be decided at the time of deployment of the spare capability.<ref name="OS SDD"> [https://www.gsc-europa.eu/sites/default/files/sites/all/files/Galileo-OS-SDD_in_force.pdf Applicable galileo Open Service (OS) Service Definition Document (SDD)]</ref>

	Each Galileo satellite is a 700 kg/1600 W class satellite, contains all the equipment needed to perform its assigned navigation and timing tasks over the course of its 12-year design life. Powered by solar arrays, with its internal components carefully shielded against the radiation prevailing in medium-Earth orbit.		Each Galileo satellite is a 700 kg/1600 W class satellite, contains all the equipment needed to perform its assigned navigation and timing tasks over the course of its 12-year design life. Powered by solar arrays, with its internal components carefully shielded against the radiation prevailing in medium-Earth orbit.

Natalia.Castrillo at 09:00, 25 June 2025

2025-06-25T09:00:02Z

← Older revision		Revision as of 09:00, 25 June 2025
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	The Galileo constellation comprises of 30 satellites placed in MEO orbit, with 10 satellites placed in each of 3 orbital planes (at 56º nominal inclination <ref name="Galileo_Early_Services">[https://www.gsc-europa.eu/galileo/system Galileo System in European GNSS Service Centre website]</ref>) distributed evenly round the equator. The active constellation comprises of 24 satellites (Walker 24/3/1), including 6 spare satellites, which can be moved to replace any failed satellite within the same plane, thereby reducing the impact of failures upon quality of service. All satellites are identical in terms of design, performance capability and fuel load. Each satellite broadcasts navigation timing signals together with navigation data providing the clock and ephemeris correction data which are essential for navigation.<ref name="Galileo_Early_Services">[https://www.gsc-europa.eu/galileo/system Galileo System in European GNSS Service Centre website]</ref>		The Galileo constellation comprises of 30 satellites placed in MEO orbit, with 10 satellites placed in each of 3 orbital planes (at 56º nominal inclination <ref name="Galileo_Early_Services">[https://www.gsc-europa.eu/galileo/system Galileo System in European GNSS Service Centre website]</ref>) distributed evenly round the equator. The active constellation comprises of 24 satellites (Walker 24/3/1), including 6 spare satellites, which can be moved to replace any failed satellite within the same plane, thereby reducing the impact of failures upon quality of service. All satellites are identical in terms of design, performance capability and fuel load. Each satellite broadcasts navigation timing signals together with navigation data providing the clock and ephemeris correction data which are essential for navigation.<ref name="Galileo_Early_Services">[https://www.gsc-europa.eu/galileo/system Galileo System in European GNSS Service Centre website]</ref>

	The orbit altitude of 23 ~~222~~ km ~~(orbital radius: 29994 Km)~~ results in ~~an orbit of repeated trace with respect to the orientation of the Earth below them,~~ that repeats ~~itself after~~ ten days ~~during which each satellite has completed seventeen revolutions~~.		The nominal orbit of a Galileo satellite is circular, with an altitude of approximately 23,229 km above the Earth’s surface. This configuration results in a ground track that repeats every 10 days, corresponding to 17 orbital revolutions over nearly ten sidereal days.

Vicente.Navarro at 12:26, 15 August 2024

2024-08-15T12:26:52Z

← Older revision		Revision as of 12:26, 15 August 2024
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	[[File:Rubidium_clock.jpg\|left\|thumb\|250px\|Rubidium clock]]		[[File:Rubidium_clock.jpg\|left\|thumb\|250px\|Rubidium clock]]

	At any time, only one clock of each type is operating. Under normal conditions, the operating maser clock produces the reference frequency from which the navigation signal is generated. Should the maser clock fail, however, the operating rubidium clock will take over instantaneously and the two reserve clocks will start up. If the problem with the failed maser clock is unique to that clock, the second maser clock will take over from the rubidium clock after a few days when it is fully operational. The rubidium clock will then go on stand-by or reserve again. In this way, by having four clocks, the Galileo spacecraft is guaranteed to generate a navigation signal at all times~~.The two types of on-board clocks are described below~~.		At any time, only one clock of each type is operating. Under normal conditions, the operating maser clock produces the reference frequency from which the navigation signal is generated. Should the maser clock fail, however, the operating rubidium clock will take over instantaneously and the two reserve clocks will start up. If the problem with the failed maser clock is unique to that clock, the second maser clock will take over from the rubidium clock after a few days when it is fully operational. The rubidium clock will then go on stand-by or reserve again. In this way, by having four clocks, the Galileo spacecraft is guaranteed to generate a navigation signal at all times.

	The '''clock monitoring and control unit''' provides the interface between the four clocks and the navigation signal generator unit (NSGU). It passes the signal from the active master clock to the NSGU and also ensures that the frequencies produced by the master clock and the active spare are in phase, so that the spare can take over instantly should the master clock fail.		The '''clock monitoring and control unit''' provides the interface between the four clocks and the navigation signal generator unit (NSGU). It passes the signal from the active master clock to the NSGU and also ensures that the frequencies produced by the master clock and the active spare are in phase, so that the spare can take over instantly should the master clock fail.

Vicente.Navarro at 11:12, 15 August 2024

2024-08-15T11:12:59Z

← Older revision		Revision as of 11:12, 15 August 2024
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	*Broadcast of navigation signals		*Broadcast of navigation signals

	The timing signals are provided by high precision on-board clocks, implemented as two (cold) redundant pairs per satellite, each pair including two different technologies, both of them being operated simultaneously. At any time, only one of each type is operating. Under normal conditions, the operating maser clock produces the reference frequency from which the navigation signal is generated. Should the maser clock fail, however, the operating rubidium clock will take over instantaneously and the two reserve clocks will start up. If the problem with the failed maser clock is unique to that clock, the second maser clock will take over from the rubidium clock after a few days when it is fully operational. The rubidium clock will then go on stand-by or reserve again. In this way, by having four clocks, the Galileo spacecraft is guaranteed to generate a navigation signal at all times.The two types of on-board clocks are described below.		The timing signals are provided by high precision on-board clocks, implemented as two (cold) redundant pairs per satellite, each pair including two different technologies, both of them being operated simultaneously:

	A '''Passive Hydrogen Maser (PHM) clock''' is the master clock on board the spacecraft. It is an atomic clock which uses the ultra stable 1.4 GHz transition in a hydrogen atom to measure time to within 0.45 ns over 12 hours.		A '''Passive Hydrogen Maser (PHM) clock''' is the master clock on board the spacecraft. It is an atomic clock which uses the ultra stable 1.4 GHz transition in a hydrogen atom to measure time to within 0.45 ns over 12 hours.
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	A '''Rubidium Atomic Frequency Standard (RAFS) clock''' will be used should the maser clock fail. It is accurate to within 1.8 ns over 12 hours.		A '''Rubidium Atomic Frequency Standard (RAFS) clock''' will be used should the maser clock fail. It is accurate to within 1.8 ns over 12 hours.
	[[File:Rubidium_clock.jpg\|left\|thumb\|250px\|Rubidium clock]]		[[File:Rubidium_clock.jpg\|left\|thumb\|250px\|Rubidium clock]]

			At any time, only one clock of each type is operating. Under normal conditions, the operating maser clock produces the reference frequency from which the navigation signal is generated. Should the maser clock fail, however, the operating rubidium clock will take over instantaneously and the two reserve clocks will start up. If the problem with the failed maser clock is unique to that clock, the second maser clock will take over from the rubidium clock after a few days when it is fully operational. The rubidium clock will then go on stand-by or reserve again. In this way, by having four clocks, the Galileo spacecraft is guaranteed to generate a navigation signal at all times.The two types of on-board clocks are described below.

	The '''clock monitoring and control unit''' provides the interface between the four clocks and the navigation signal generator unit (~~NSU~~). It passes the signal from the active master clock to the ~~NSU~~ and also ensures that the frequencies produced by the master clock and the active spare are in phase, so that the spare can take over instantly should the master clock fail.		The '''clock monitoring and control unit''' provides the interface between the four clocks and the navigation signal generator unit (NSGU). It passes the signal from the active master clock to the NSGU and also ensures that the frequencies produced by the master clock and the active spare are in phase, so that the spare can take over instantly should the master clock fail.

	The '''navigation signal generator, frequency generator and up-conversion units''' are in charge of generating the navigation signals using input from the clock monitoring unit and the up-linked navigation and integrity data from the C-band antenna. The navigation signals are converted to L-band for broadcast to users.		The '''navigation signal generator, frequency generator and up-conversion units''' are in charge of generating the navigation signals using input from the clock monitoring unit and the up-linked navigation and integrity data from the C-band antenna. The navigation signals are converted to L-band for broadcast to users.

Vicente.Navarro: Reverted edits by Vicente.Navarro (talk) to last revision by Gema.Cueto

2024-08-12T14:56:13Z

Reverted edits by Vicente.Navarro (talk) to last revision by Gema.Cueto

← Older revision		Revision as of 14:56, 12 August 2024
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	*Broadcast of navigation signals		*Broadcast of navigation signals

	The timing signals are provided by high precision on-board clocks, implemented as two (cold) redundant pairs per satellite, each pair including two different technologies, both of them being operated simultaneously. At any time, only one of each type is operating. Under normal conditions, the operating ~~master~~ clock produces the reference frequency from which the navigation signal is generated. Should the ~~master~~ clock fail, however, the operating rubidium clock will take over instantaneously and the two reserve clocks will start up. If the problem with the failed ~~master~~ clock is unique to that clock, the second ~~master~~ clock will take over from the rubidium clock after a few days when it is fully operational. The rubidium clock will then go on stand-by or reserve again. In this way, by having four clocks, the Galileo spacecraft is guaranteed to generate a navigation signal at all times.The two types of on-board clocks are described below.		The timing signals are provided by high precision on-board clocks, implemented as two (cold) redundant pairs per satellite, each pair including two different technologies, both of them being operated simultaneously. At any time, only one of each type is operating. Under normal conditions, the operating maser clock produces the reference frequency from which the navigation signal is generated. Should the maser clock fail, however, the operating rubidium clock will take over instantaneously and the two reserve clocks will start up. If the problem with the failed maser clock is unique to that clock, the second maser clock will take over from the rubidium clock after a few days when it is fully operational. The rubidium clock will then go on stand-by or reserve again. In this way, by having four clocks, the Galileo spacecraft is guaranteed to generate a navigation signal at all times.The two types of on-board clocks are described below.

	A '''Passive Hydrogen ~~Master~~ (PHM) clock''' is the master clock on board the spacecraft. It is an atomic clock which uses the ultra stable 1.4 GHz transition in a hydrogen atom to measure time to within 0.45 ns over 12 hours.		A '''Passive Hydrogen Maser (PHM) clock''' is the master clock on board the spacecraft. It is an atomic clock which uses the ultra stable 1.4 GHz transition in a hydrogen atom to measure time to within 0.45 ns over 12 hours.

	A '''Rubidium Atomic Frequency Standard (RAFS) clock''' will be used should the ~~master~~ clock fail. It is accurate to within 1.8 ns over 12 hours.		A '''Rubidium Atomic Frequency Standard (RAFS) clock''' will be used should the maser clock fail. It is accurate to within 1.8 ns over 12 hours.
	[[File:Rubidium_clock.jpg\|left\|thumb\|250px\|Rubidium clock]]		[[File:Rubidium_clock.jpg\|left\|thumb\|250px\|Rubidium clock]]

Vicente.Navarro at 14:54, 12 August 2024

2024-08-12T14:54:53Z

← Older revision		Revision as of 14:54, 12 August 2024
Line 98:		Line 98:
	*Broadcast of navigation signals		*Broadcast of navigation signals

	The timing signals are provided by high precision on-board clocks, implemented as two (cold) redundant pairs per satellite, each pair including two different technologies, both of them being operated simultaneously. At any time, only one of each type is operating. Under normal conditions, the operating ~~maser~~ clock produces the reference frequency from which the navigation signal is generated. Should the ~~maser~~ clock fail, however, the operating rubidium clock will take over instantaneously and the two reserve clocks will start up. If the problem with the failed ~~maser~~ clock is unique to that clock, the second ~~maser~~ clock will take over from the rubidium clock after a few days when it is fully operational. The rubidium clock will then go on stand-by or reserve again. In this way, by having four clocks, the Galileo spacecraft is guaranteed to generate a navigation signal at all times.The two types of on-board clocks are described below.		The timing signals are provided by high precision on-board clocks, implemented as two (cold) redundant pairs per satellite, each pair including two different technologies, both of them being operated simultaneously. At any time, only one of each type is operating. Under normal conditions, the operating master clock produces the reference frequency from which the navigation signal is generated. Should the master clock fail, however, the operating rubidium clock will take over instantaneously and the two reserve clocks will start up. If the problem with the failed master clock is unique to that clock, the second master clock will take over from the rubidium clock after a few days when it is fully operational. The rubidium clock will then go on stand-by or reserve again. In this way, by having four clocks, the Galileo spacecraft is guaranteed to generate a navigation signal at all times.The two types of on-board clocks are described below.

	A '''Passive Hydrogen ~~Maser~~ (PHM) clock''' is the master clock on board the spacecraft. It is an atomic clock which uses the ultra stable 1.4 GHz transition in a hydrogen atom to measure time to within 0.45 ns over 12 hours.		A '''Passive Hydrogen Master (PHM) clock''' is the master clock on board the spacecraft. It is an atomic clock which uses the ultra stable 1.4 GHz transition in a hydrogen atom to measure time to within 0.45 ns over 12 hours.

	A '''Rubidium Atomic Frequency Standard (RAFS) clock''' will be used should the ~~maser~~ clock fail. It is accurate to within 1.8 ns over 12 hours.		A '''Rubidium Atomic Frequency Standard (RAFS) clock''' will be used should the master clock fail. It is accurate to within 1.8 ns over 12 hours.
	[[File:Rubidium_clock.jpg\|left\|thumb\|250px\|Rubidium clock]]		[[File:Rubidium_clock.jpg\|left\|thumb\|250px\|Rubidium clock]]

Gema.Cueto: /* Galileo Metadata */

2021-07-22T07:04:32Z

Galileo Metadata

← Older revision		Revision as of 07:04, 22 July 2021
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	The Galileo Metadata can be found in the GNSS Service Centre Web Page. See the following link:		The Galileo Metadata can be found in the GNSS Service Centre Web Page. See the following link:

	[https://www.gsc-europa.eu/support-to-developers/galileo-satellite-metadata ~~\|https://www.gsc-europa.eu/support-to-developers/galileo-satellite-metadata]~~		https://www.gsc-europa.eu/support-to-developers/galileo-satellite-metadata

	==Satellites Names and Launching ==		==Satellites Names and Launching ==

Gema.Cueto: /* Galileo Metadata */

2021-07-22T07:02:12Z

Galileo Metadata

← Older revision		Revision as of 07:02, 22 July 2021
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	The Galileo Metadata can be found in the GNSS Service Centre Web Page. See the following link:		The Galileo Metadata can be found in the GNSS Service Centre Web Page. See the following link:

	[https://www.gsc-europa.eu/support-to-developers/galileo-satellite-metadata \| https://www.gsc-europa.eu/support-to-developers/galileo-satellite-metadata]		[https://www.gsc-europa.eu/support-to-developers/galileo-satellite-metadata \|https://www.gsc-europa.eu/support-to-developers/galileo-satellite-metadata]

	==Satellites Names and Launching ==		==Satellites Names and Launching ==

Gema.Cueto: /* Galileo Metadata */

2021-07-22T07:01:56Z

Galileo Metadata

← Older revision		Revision as of 07:01, 22 July 2021
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	The Galileo Metadata can be found in the GNSS Service Centre Web Page. See the following link:		The Galileo Metadata can be found in the GNSS Service Centre Web Page. See the following link:

	[https://www.gsc-europa.eu/support-to-developers/galileo-satellite-metadata\| https://www.gsc-europa.eu/support-to-developers/galileo-satellite-metadata]		[https://www.gsc-europa.eu/support-to-developers/galileo-satellite-metadata \| https://www.gsc-europa.eu/support-to-developers/galileo-satellite-metadata]

	==Satellites Names and Launching ==		==Satellites Names and Launching ==

Gema.Cueto: /* Galileo Metadata */

2021-07-21T15:10:31Z

Galileo Metadata

← Older revision		Revision as of 15:10, 21 July 2021
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	==Galileo Metadata ==		==Galileo Metadata ==
	The Galileo Metadata can be found in the GNSS Service Centre Web Page. See the following link:		The Galileo Metadata can be found in the GNSS Service Centre Web Page. See the following link:

	[https://www.gsc-europa.eu/support-to-developers/galileo-satellite-metadata\| https://www.gsc-europa.eu/support-to-developers/galileo-satellite-metadata]		[https://www.gsc-europa.eu/support-to-developers/galileo-satellite-metadata\| https://www.gsc-europa.eu/support-to-developers/galileo-satellite-metadata]