SBAS Fundamentals - Revision history

Claudia.Prajanu at 08:34, 27 July 2018

2018-07-27T08:34:11Z

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	* Compatibility to other avionics equipment, in particular Flight Management Systems (FMS).		* Compatibility to other avionics equipment, in particular Flight Management Systems (FMS).

	The SoL civil aviation certified equipment is in the highest rank with respect its cost. There exist a large number of certified receivers manufacturers worldwide both in the US (GARMIN, Honeywell, Rockwell Collins, General Avionics, etc) and in Europe (see complete list in EASA homepage<ref>[~~http~~://www.easa.europa.eu/~~certification/docs/etso-authorisations/etsoa.pdf~~ List of ETSO Authorisations (European Aviation Safety Agency)]</ref>).		The SoL civil aviation certified equipment is in the highest rank with respect its cost. There exist a large number of certified receivers manufacturers worldwide both in the US (GARMIN, Honeywell, Rockwell Collins, General Avionics, etc) and in Europe (see complete list in EASA homepage<ref>[https://www.easa.europa.eu/ List of ETSO Authorisations (European Aviation Safety Agency)]</ref>).

	The Open Service (OS) targets low cost, general purpose GNSS equipment that uses the SBAS SIS to provide the user with an enhanced accuracy performance in comparison with the one provided by a standalone GPS device. In comparison with the certification requirements of the user equipment above, user equipment is not necessarily compliant with the RTCA MOPS DO 229 processing rules, but might only make use of the processing algorithms that render the accuracy corrections provided by the SBAS SIS.		The Open Service (OS) targets low cost, general purpose GNSS equipment that uses the SBAS SIS to provide the user with an enhanced accuracy performance in comparison with the one provided by a standalone GPS device. In comparison with the certification requirements of the user equipment above, user equipment is not necessarily compliant with the RTCA MOPS DO 229 processing rules, but might only make use of the processing algorithms that render the accuracy corrections provided by the SBAS SIS.

Filipe.Pelica: Included editor logo.

2014-09-18T16:38:20Z

Included editor logo.

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Winfried.Schroedter2: /* References */ better place in category list

2014-09-10T10:57:12Z

References: better place in category list

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	[[Category:Fundamentals]]		[[Category:Fundamentals]]
	[[Category:Other SBAS]]		[[Category:Other SBAS\|!]]

Carlos.Lopez at 11:15, 23 February 2012

2012-02-23T11:15:48Z

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	{{Article Infobox2		{{Article Infobox2
	\|Category=Fundamentals		\|Category=Fundamentals
	\|Editors=GMV ~~A.D.~~		\|Editors=GMV
	\|Level=Basic		\|Level=Basic
	\|YearOfPublication=2011		\|YearOfPublication=2011

Carlos.Lopez at 10:29, 23 February 2012

2012-02-23T10:29:16Z

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	{{Article Infobox2		{{Article Infobox2
	\|Category=Fundamentals		\|Category=Fundamentals
	\|~~Title={{PAGENAME}}~~		\|Editors=GMV A.D.
	~~\|Authors~~=GMV
	\|Level=Basic		\|Level=Basic
	\|YearOfPublication=2011		\|YearOfPublication=2011
	\|~~Logo~~=~~GMV~~		\|Title={{PAGENAME}}
	}}		}}
	A Satellite-based Augmentation System (SBAS) is a civil aviation safety-critical system that supports wide-area or regional augmentation – even continental scale - through the use of geostationary (GEO) satellites which broadcast the augmentation information.<ref name="GNSS Aug">[[Wikipedia:GNSS augmentation]]</ref><ref name="Kaplan">E.D. Kaplan, C.J. Hegarty, ''Understanding GPS Principles and Applications”, 2nd Ed., Artch House, ISBN 1-58053-894-0, 2006.</ref> A SBAS augments primary GNSS constellation(s) by providing GEO ranging, [[Integrity\|integrity]] and correction information. While the main goal of SBAS is to provide [[Integrity\|integrity]] assurance, it also increases the [[Accuracy\|accuracy]] with position errors below 1 meter (1 sigma).		A Satellite-based Augmentation System (SBAS) is a civil aviation safety-critical system that supports wide-area or regional augmentation – even continental scale - through the use of geostationary (GEO) satellites which broadcast the augmentation information.<ref name="GNSS Aug">[[Wikipedia:GNSS augmentation]]</ref><ref name="Kaplan">E.D. Kaplan, C.J. Hegarty, ''Understanding GPS Principles and Applications”, 2nd Ed., Artch House, ISBN 1-58053-894-0, 2006.</ref> A SBAS augments primary GNSS constellation(s) by providing GEO ranging, [[Integrity\|integrity]] and correction information. While the main goal of SBAS is to provide [[Integrity\|integrity]] assurance, it also increases the [[Accuracy\|accuracy]] with position errors below 1 meter (1 sigma).

Jose.Caro at 18:17, 28 September 2011

2011-09-28T18:17:18Z

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	As indicated in the table above, the performance requirements are expressed in terms of four quantitative concepts, many of them to be interpreted as probabilistic figures:		As indicated in the table above, the performance requirements are expressed in terms of four quantitative concepts, many of them to be interpreted as probabilistic figures:
	* '''Accuracy''': is expressed in terms of Navigation System Error (NSE) as the difference between the real position of the aircraft and the position provided by the airborne equipment. A SBAS assures the compliance with respect the accuracy requirements by providing to the user corrections to the satellite orbit and clock errors as well as to the ionospheric residual propagation error. For LPV200 operations, new requirements have been proposed distinguishing the fault-free and the system failure conditions.<ref>NSP WGW October 2008 Report – Attachment G, Recommended changes to Annex 10, Volume 1, Section 3.7</ref>		* '''Accuracy''': is expressed in terms of Navigation System Error (NSE) as the difference between the real position of the aircraft and the position provided by the airborne equipment. A SBAS assures the compliance with respect the accuracy requirements by providing to the user corrections to the satellite orbit and clock errors as well as to the ionospheric residual propagation error. For LPV200 operations, new requirements have been proposed distinguishing the fault-free and the system failure conditions.<ref>NSP WGW October 2008 Report – Attachment G, Recommended changes to Annex 10, Volume 1, Section 3.7</ref>
	* '''Integrity''': is defined by [http://www.icao.org ICAO] as a measure of the trust that can be placed in the correctness of the information supplied by the system. This general statement is expressed at the SBAS system level as the maximum allowable probability that the navigation position error exceeds alarm limit and the navigation system does not alert the pilot in a time less than the time to alert. The SBAS assures the integrity requirements by:		* '''Integrity''': is defined by [http://www.icao.org ICAO] as a measure of the trust that can be placed in the correctness of the information supplied by the system.<ref name="ICAO_SARPS"/> This general statement is expressed at the SBAS system level as the maximum allowable probability that the navigation position error exceeds alarm limit and the navigation system does not alert the pilot in a time less than the time to alert. The SBAS assures the integrity requirements by:
	** Providing to the user satellite and/or ionospheric alarms in order to inform the user to reject the corresponding satellite/ionospheric corrections in its positioning computation.		** Providing to the user satellite and/or ionospheric alarms in order to inform the user to reject the corresponding satellite/ionospheric corrections in its positioning computation.
	** Providing to the user Horizontal and Vertical Protection Level information (HPL, VPL) in order to assess the availability of the system, by comparing these PLs with the corresponding Alarm Limits (AL) for a given phase of flight (see next table). The SBAS computes and broadcasts integrity bounds to the satellite orbit and clock (UDRE) corrections as well as to the ionospheric corrections errors (GIVE) so that the user is able to compute a PL that over bounds the navigation system error experienced by the user with the integrity risk requirement.		** Providing to the user Horizontal and Vertical Protection Level information (HPL, VPL) in order to assess the availability of the system, by comparing these PLs with the corresponding Alarm Limits (AL) for a given phase of flight (see next table). The SBAS computes and broadcasts integrity bounds to the satellite orbit and clock (UDRE) corrections as well as to the ionospheric corrections errors (GIVE) so that the user is able to compute a PL that over bounds the navigation system error experienced by the user with the integrity risk requirement.
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	* '''Continuity''': is the probability that the specified system performance will be maintained for the duration of a phase of operation, presuming that the system was available at the beginning of that phase of operation and was predicted to operate throughout the operation.<ref name="~~MOPS~~"~~>[http:~~/~~/www.rtca.org RTCA] MOPS DO-229-D, ''Minimum Operational Performance Standards for Global Positioning System/Wide Area Augmentation System airborne equipment''</ref~~> Lack of continuity means that the operation must be aborted (with the associated risk).		* '''Continuity''': is the probability that the specified system performance will be maintained for the duration of a phase of operation, presuming that the system was available at the beginning of that phase of operation and was predicted to operate throughout the operation.<ref name="ICAO_SARPS"/> Lack of continuity means that the operation must be aborted (with the associated risk).
	* '''Availability''': is the probability that the navigation service is available at the beginning of the planned operation. A SBAS is considered available when the accuracy, integrity and continuity requirements are met and it is measured in terms of probability of the system being available for any given user at any given time. In practice, the availability is computed by measuring the probability of a protection level being below its corresponding alarm limit. It should be noted that a lack of availability is not a safety concern but prevents the nominal operation of the system, and implies an associated impact on the service operation status.		* '''Availability''': is the probability that the navigation service is available at the beginning of the planned operation. A SBAS is considered available when the accuracy, integrity and continuity requirements are met and it is measured in terms of probability of the system being available for any given user at any given time. In practice, the availability is computed by measuring the probability of a protection level being below its corresponding alarm limit. It should be noted that a lack of availability is not a safety concern but prevents the nominal operation of the system, and implies an associated impact on the service operation status.

Jose.Caro at 18:10, 28 September 2011

2011-09-28T18:10:00Z

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	* '''Continuity''': is the probability that the specified system performance will be maintained for the duration of a phase of operation, presuming that the system was available at the beginning of that phase of operation and was predicted to operate throughout the operation. Lack of continuity means that the operation must be aborted (with the associated risk).		* '''Continuity''': is the probability that the specified system performance will be maintained for the duration of a phase of operation, presuming that the system was available at the beginning of that phase of operation and was predicted to operate throughout the operation.<ref name="MOPS">[http://www.rtca.org RTCA] MOPS DO-229-D, ''Minimum Operational Performance Standards for Global Positioning System/Wide Area Augmentation System airborne equipment''</ref> Lack of continuity means that the operation must be aborted (with the associated risk).
	* '''Availability''': is the probability that the navigation service is available at the beginning of the planned operation. A SBAS is considered available when the accuracy, integrity and continuity requirements are met and it is measured in terms of probability of the system being available for any given user at any given time. In practice, the availability is computed by measuring the probability of a protection level being below its corresponding alarm limit. It should be noted that a lack of availability is not a safety concern but prevents the nominal operation of the system, and implies an associated impact on the service operation status.		* '''Availability''': is the probability that the navigation service is available at the beginning of the planned operation. A SBAS is considered available when the accuracy, integrity and continuity requirements are met and it is measured in terms of probability of the system being available for any given user at any given time. In practice, the availability is computed by measuring the probability of a protection level being below its corresponding alarm limit. It should be noted that a lack of availability is not a safety concern but prevents the nominal operation of the system, and implies an associated impact on the service operation status.

Rui.Pereira at 17:31, 29 June 2011

2011-06-29T17:31:27Z

Jose.Caro: IRKP Actions 12 and 13 closure.

2011-06-27T13:42:22Z

IRKP Actions 12 and 13 closure.

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	As indicated in the table above, the performance requirements are expressed in terms of four quantitative concepts, many of them to be interpreted as probabilistic figures:		As indicated in the table above, the performance requirements are expressed in terms of four quantitative concepts, many of them to be interpreted as probabilistic figures:
	* '''Accuracy''': is expressed in terms of Navigation System Error (NSE) as the difference between the real position of the aircraft and the position provided by the airborne equipment. A SBAS assures the compliance with respect the accuracy requirements by providing to the user corrections to the satellite orbit and clock errors as well as to the ionospheric residual propagation error.		* '''Accuracy''': is expressed in terms of Navigation System Error (NSE) as the difference between the real position of the aircraft and the position provided by the airborne equipment. A SBAS assures the compliance with respect the accuracy requirements by providing to the user corrections to the satellite orbit and clock errors as well as to the ionospheric residual propagation error. For LPV200 operations, new requirements have been proposed distinguishing the fault-free and the system failure conditions.<ref>NSP WGW October 2008 Report – Attachment G, Recommended changes to Annex 10, Volume 1, Section 3.7</ref>
	* '''Integrity''': is defined by [http://www.icao.org ICAO] as a measure of the trust that can be placed in the correctness of the information supplied by the system. This general statement is expressed at the SBAS system level as the maximum allowable probability that the navigation position error exceeds alarm limit and the navigation system does not alert the pilot in a time less than the time to alert. The SBAS assures the integrity requirements by:		* '''Integrity''': is defined by [http://www.icao.org ICAO] as a measure of the trust that can be placed in the correctness of the information supplied by the system. This general statement is expressed at the SBAS system level as the maximum allowable probability that the navigation position error exceeds alarm limit and the navigation system does not alert the pilot in a time less than the time to alert. The SBAS assures the integrity requirements by:
	** Providing to the user satellite and/or ionospheric alarms in order to inform the user to reject the corresponding satellite/ionospheric corrections in its positioning computation.		** Providing to the user satellite and/or ionospheric alarms in order to inform the user to reject the corresponding satellite/ionospheric corrections in its positioning computation.

Jose.Caro: Small correction of typo when referring to ICAO SARPS.

2011-04-07T11:29:51Z

Small correction of typo when referring to ICAO SARPS.

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	The SBAS delivers to the user the corrections and integrity data as well as some ancillary information (timing, degradation parameters, etc.) through messages encoded in the signal. The specification of the SBAS message data format is contained in the [http://www.icao.org ICAO] SARPS Appendix B for the aspects related with the signal in space, as well as in the RTCA MOPS DO-229D for the minimum performance requirements applicable to the airborne SBAS receiver equipment. The format of the messages is thoroughly explained in the article [[The EGNOS SBAS Message Format Explained]].		The SBAS delivers to the user the corrections and integrity data as well as some ancillary information (timing, degradation parameters, etc.) through messages encoded in the signal. The specification of the SBAS message data format is contained in the [http://www.icao.org ICAO] SARPS Appendix B for the aspects related with the signal in space, as well as in the RTCA MOPS DO-229D for the minimum performance requirements applicable to the airborne SBAS receiver equipment. The format of the messages is thoroughly explained in the article [[The EGNOS SBAS Message Format Explained]].

	The SBAS satellite shall transmit a GPS-like L1 (1574.42 MHz) signal, modulated with a Coarse/Acquisition Pseudo-Random Noise (PRN) code. The SBAS L1 radiofrequency characteristics are:<ref name=~~”ICAO SARPS”~~>[http://www.icao.org ICAO] Standards and Recommended Practices, Annex 10, Volume 1 Radio Navigation Aids, July 2006</ref>		The SBAS satellite shall transmit a GPS-like L1 (1574.42 MHz) signal, modulated with a Coarse/Acquisition Pseudo-Random Noise (PRN) code. The SBAS L1 radiofrequency characteristics are:<ref name="ICAO_SARPS">[http://www.icao.org ICAO] Standards and Recommended Practices, Annex 10, Volume 1 Radio Navigation Aids, July 2006</ref>

	{\| class="wikitable"		{\| class="wikitable"
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	==SBAS Performances==		==SBAS Performances==
	The SBAS performances are defined with respect to the level of service that the system is designed to provide. The main source for SBAS performances comes from civil aviation navigation safety requirements and they are different for each civil aviation operation.<ref name=~~”ICAO SARPS”~~/>~~insert reference</ref>~~		The SBAS performances are defined with respect to the level of service that the system is designed to provide. The main source for SBAS performances comes from civil aviation navigation safety requirements and they are different for each civil aviation operation.<ref name="ICAO_SARPS"/>

	{\| class="wikitable"		{\| class="wikitable"
	\|-		\|-

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	A Satellite-based Augmentation System (SBAS) is a civil aviation safety-critical system that supports wide-area or regional augmentation – even continental scale - through the use of geostationary (GEO) satellites which broadcast the augmentation information.<ref name="GNSS Aug">[[Wikipedia:GNSS augmentation]]</ref><ref name="Kaplan">E.D. Kaplan, C.J. Hegarty, ''Understanding GPS Principles and Applications”, 2nd Ed., Artch House, ISBN 1-58053-894-0, 2006.</ref> A SBAS augments primary GNSS constellation(s) by providing GEO ranging, [[Integrity\|integrity]] and correction information. While the main goal of SBAS is to provide [[Integrity\|integrity]] assurance, it also increases the [[Accuracy\|accuracy]] with position errors below 1 ~~metre~~ (1 sigma).		A Satellite-based Augmentation System (SBAS) is a civil aviation safety-critical system that supports wide-area or regional augmentation – even continental scale - through the use of geostationary (GEO) satellites which broadcast the augmentation information.<ref name="GNSS Aug">[[Wikipedia:GNSS augmentation]]</ref><ref name="Kaplan">E.D. Kaplan, C.J. Hegarty, ''Understanding GPS Principles and Applications”, 2nd Ed., Artch House, ISBN 1-58053-894-0, 2006.</ref> A SBAS augments primary GNSS constellation(s) by providing GEO ranging, [[Integrity\|integrity]] and correction information. While the main goal of SBAS is to provide [[Integrity\|integrity]] assurance, it also increases the [[Accuracy\|accuracy]] with position errors below 1 meter (1 sigma).

	The ground infrastructure includes the accurately-surveyed sensor stations which receive the data from the primary GNSS satellites and a Processing Facility ~~Centre~~ which computes [[Integrity\|integrity]], corrections and GEO ranging data forming the SBAS signal-in-space (SIS). The SBAS GEO satellites relay the SIS to the SBAS users which determine their position and time information. For this, they use measurements and satellite positions both from the primary GNSS constellation(s) and the SBAS GEO satellites and apply the SBAS correction data and its [[Integrity\|integrity]].		The ground infrastructure includes the accurately-surveyed sensor stations which receive the data from the primary GNSS satellites and a Processing Facility Center which computes [[Integrity\|integrity]], corrections and GEO ranging data forming the SBAS signal-in-space (SIS). The SBAS GEO satellites relay the SIS to the SBAS users which determine their position and time information. For this, they use measurements and satellite positions both from the primary GNSS constellation(s) and the SBAS GEO satellites and apply the SBAS correction data and its [[Integrity\|integrity]].

	The augmentation information provided by SBAS covers corrections and [[Integrity\|integrity]] for satellite position errors, satellite clock/time errors and errors induced by the estimation of the delay of the signal while crossing the [[Ionospheric Delay\|ionosphere]]. For the errors induced by the estimation of the delay caused by the [[Tropospheric Delay\|troposphere]] and its integrity, the user applies a [[Tropospheric Delay\|tropospheric delay]] model.		The augmentation information provided by SBAS covers corrections and [[Integrity\|integrity]] for satellite position errors, satellite clock/time errors and errors induced by the estimation of the delay of the signal while crossing the [[Ionospheric Delay\|ionosphere]]. For the errors induced by the estimation of the delay caused by the [[Tropospheric Delay\|troposphere]] and its integrity, the user applies a [[Tropospheric Delay\|tropospheric delay]] model.
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	* '''Integrity''': is defined by [http://www.icao.org ICAO] as a measure of the trust that can be placed in the correctness of the information supplied by the system. This general statement is expressed at the SBAS system level as the maximum allowable probability that the navigation position error exceeds alarm limit and the navigation system does not alert the pilot in a time less than the time to alert. The SBAS assures the integrity requirements by:		* '''Integrity''': is defined by [http://www.icao.org ICAO] as a measure of the trust that can be placed in the correctness of the information supplied by the system. This general statement is expressed at the SBAS system level as the maximum allowable probability that the navigation position error exceeds alarm limit and the navigation system does not alert the pilot in a time less than the time to alert. The SBAS assures the integrity requirements by:
	** Providing to the user satellite and/or ionospheric alarms in order to inform the user to reject the corresponding satellite/ionospheric corrections in its positioning computation.		** Providing to the user satellite and/or ionospheric alarms in order to inform the user to reject the corresponding satellite/ionospheric corrections in its positioning computation.
	** Providing to the user Horizontal and Vertical Protection Level information (HPL, VPL) in order to assess the availability of the system, by comparing these PLs with the corresponding Alarm Limits (AL) for a given phase of flight (see next ~~tabel~~). The SBAS computes and broadcasts integrity bounds to the satellite orbit and clock (UDRE) corrections as well as to the ionospheric corrections errors (GIVE) so that the user is able to compute a PL that over bounds the navigation system error experienced by the user with the integrity risk requirement.		** Providing to the user Horizontal and Vertical Protection Level information (HPL, VPL) in order to assess the availability of the system, by comparing these PLs with the corresponding Alarm Limits (AL) for a given phase of flight (see next table). The SBAS computes and broadcasts integrity bounds to the satellite orbit and clock (UDRE) corrections as well as to the ionospheric corrections errors (GIVE) so that the user is able to compute a PL that over bounds the navigation system error experienced by the user with the integrity risk requirement.

	{\| class="wikitable"		{\| class="wikitable"
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	* '''Continuity''': is the probability that the specified system performance will be maintained for the duration of a phase of operation, presuming that the system was available at the beginning of that phase of operation and was predicted to operate throughout the operation. Lack of continuity means that the operation must be aborted (with the associated risk).		* '''Continuity''': is the probability that the specified system performance will be maintained for the duration of a phase of operation, presuming that the system was available at the beginning of that phase of operation and was predicted to operate throughout the operation. Lack of continuity means that the operation must be aborted (with the associated risk).
	* '''Availability''': is the probability that the navigation service is available at the beginning of the planned operation. A SBAS is considered available when the accuracy, integrity and continuity requirements are met and it is measured in terms of probability of the system being available for any given user at any given time. In practice, the availability is computed by measuring the probability of a ~~protrection~~ level being below its corresponding alarm limit. It should be noted that a lack of availability is not a safety concern but prevents the nominal operation of the system, and implies an associated impact on the service operation status.		* '''Availability''': is the probability that the navigation service is available at the beginning of the planned operation. A SBAS is considered available when the accuracy, integrity and continuity requirements are met and it is measured in terms of probability of the system being available for any given user at any given time. In practice, the availability is computed by measuring the probability of a protection level being below its corresponding alarm limit. It should be noted that a lack of availability is not a safety concern but prevents the nominal operation of the system, and implies an associated impact on the service operation status.

	==SBAS Architecture==		==SBAS Architecture==
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	* Ground segment comprising all the ground elements in charge of the provision of the SBAS navigation message. The main elements are:		* Ground segment comprising all the ground elements in charge of the provision of the SBAS navigation message. The main elements are:
	** Monitoring Station Network.		** Monitoring Station Network.
	** Processing Facility ~~Centre~~.		** Processing Facility Center.
	** GEO Satellite Control ~~Centre~~.		** GEO Satellite Control Center.
	** Communication Layer.		** Communication Layer.
	* Support segment comprising all the elements need to support the correct operation and maintenance of the SBAS: configuration control, performance evaluation, maintenance and development, help desk, etc.		* Support segment comprising all the elements need to support the correct operation and maintenance of the SBAS: configuration control, performance evaluation, maintenance and development, help desk, etc.
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	To achieve this objective, the Ground Mission Segment is typically broken down into the following subsystems:		To achieve this objective, the Ground Mission Segment is typically broken down into the following subsystems:
	*Monitoring Station Network: Its purpose is to collect data from the satellites that are to be augmented. This is performed by a network of GNSS receivers.		*Monitoring Station Network: Its purpose is to collect data from the satellites that are to be augmented. This is performed by a network of GNSS receivers.
	*Processing Facility ~~Centre~~: It is in charge of processing the data provided by the Monitoring Station Network to generate the messages to be broadcasted to the satellites.		*Processing Facility Center: It is in charge of processing the data provided by the Monitoring Station Network to generate the messages to be broadcasted to the satellites.
	*GEO Satellite Control ~~Centre~~: It is in charge of generating the signal with the message provided by the Processing Facility ~~Centre~~ and up-linking it to the GEO satellites.		*GEO Satellite Control Center: It is in charge of generating the signal with the message provided by the Processing Facility Center and up-linking it to the GEO satellites.
	*Communication Layer: It interconnects the different elements of the Ground Segment.		*Communication Layer: It interconnects the different elements of the Ground Segment.

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	** Integrated robustness against known threats (e.g. ''evil'' waveforms detection).		** Integrated robustness against known threats (e.g. ''evil'' waveforms detection).

	====Processing Facility ~~Centre~~====		====Processing Facility Center====
	[[File:egnos_cpfps.png\|CPFPS, component of the EGNOS Central Processing Facility\|thumb\|right\|200px]]		[[File:egnos_cpfps.png\|CPFPS, component of the EGNOS Central Processing Facility\|thumb\|right\|200px]]
	The Processing Facility ~~Centre~~ is one of the critical elements of the SBAS system as it is charge of generating the augmentation information for the user, playing a major role in the achievement of the SBAS performance requirements.		The Processing Facility Center is one of the critical elements of the SBAS system as it is charge of generating the augmentation information for the user, playing a major role in the achievement of the SBAS performance requirements.

	The Processing Facility ~~Centre~~ is in charge of the following functions:		The Processing Facility Center is in charge of the following functions:
	* Process all input data from the Monitoring Station Network.		* Process all input data from the Monitoring Station Network.
	* Estimate the satellite corrections, ionospheric model and error variance terms.		* Estimate the satellite corrections, ionospheric model and error variance terms.
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	* Format the outputs according to the SBAS standards.		* Format the outputs according to the SBAS standards.

	The Processing Facility ~~Centre~~ has a very strong algorithmic load, as it has to solve the following challenges:		The Processing Facility Center has a very strong algorithmic load, as it has to solve the following challenges:
	* Advanced models for satellite orbit determination (breaking frontiers in GEO orbit and clock determination).		* Advanced models for satellite orbit determination (breaking frontiers in GEO orbit and clock determination).
	* Determination of the SBAS reference time and satellite clock corrections with better than 2 ns accuracy.		* Determination of the SBAS reference time and satellite clock corrections with better than 2 ns accuracy.
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	* Integrity estimation valid for wide-areas with demanding performance requirements.		* Integrity estimation valid for wide-areas with demanding performance requirements.

	====GEO Satellite Control ~~Centre~~====		====GEO Satellite Control Center====
	[[File:egnos_nles_test.png\|Test diagram for EGNOS uplink station\|thumb\|right\|200px]]		[[File:egnos_nles_test.png\|Test diagram for EGNOS uplink station\|thumb\|right\|200px]]
	GEO Satellite Control ~~Centre~~ function is to relay the SBAS messages computed by the Processing Facility ~~Centre~~ to the GEO satellites. Its functions include:		GEO Satellite Control Center function is to relay the SBAS messages computed by the Processing Facility Center to the GEO satellites. Its functions include:
	* Codify the GPS-like signal encoding. In particular, the preparation of the signal generation as well as the PRN encoding.		* Codify the GPS-like signal encoding. In particular, the preparation of the signal generation as well as the PRN encoding.
	* Modulate the SBAS message information provided by the Processing Facility ~~Centre~~ into the signal.		* Modulate the SBAS message information provided by the Processing Facility Center into the signal.
	* Synchronize the timing of the signal to the SBAS reference time.		* Synchronize the timing of the signal to the SBAS reference time.
	* Control de time synchronization between the carrier and code components of the uplink signal (core-carrier coherency).		* Control de time synchronization between the carrier and code components of the uplink signal (core-carrier coherency).
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	* Service Volume Simulators in charge of evaluating the overall SBAS performances over the service area under a set of controlled conditions.		* Service Volume Simulators in charge of evaluating the overall SBAS performances over the service area under a set of controlled conditions.
	* Performance Analysis Tools in charge of measuring all the performance concepts at:		* Performance Analysis Tools in charge of measuring all the performance concepts at:
	** system level by ~~analysing~~ the Signal in Space information and checking the accuracy, integrity, continuity and availability features but using concepts based in the errors available at pseudorange domain.		** system level by analyzing the Signal in Space information and checking the accuracy, integrity, continuity and availability features but using concepts based in the errors available at pseudorange domain.
	** user point of view level, by ~~analysing~~ user data (including local conditions) and applying user-related algorithms (see [[SBAS Standards\|SBAS standards]]).		** user point of view level, by analyzing user data (including local conditions) and applying user-related algorithms (see [[SBAS Standards\|SBAS standards]]).
	* On-line monitoring tools for tracking the system ~~behaviour~~ in real time and collecting system failure and anomalies. These elements also support the system operation by predicting the expected ~~behaviour~~ of the system and provide warnings as system outages or degradations. They also provide warnings to external users.		* On-line monitoring tools for tracking the system behavior in real time and collecting system failure and anomalies. These elements also support the system operation by predicting the expected behavior of the system and provide warnings as system outages or degradations. They also provide warnings to external users.
	* Archiving tools supporting the data archiving. The data comprises both all the internal information generated by the system as well as external data (satellite reference orbit and clock data, ionospheric information, outages, etc).		* Archiving tools supporting the data archiving. The data comprises both all the internal information generated by the system as well as external data (satellite reference orbit and clock data, ionospheric information, outages, etc).
	* Application test benches to support applications by generating test scenarios for their certification and performance verification. They are able to plug different application software or equipment for homologation purposes.		* Application test benches to support applications by generating test scenarios for their certification and performance verification. They are able to plug different application software or equipment for homologation purposes.