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{{Article Infobox2
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|Authors=GMV.
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|YearOfPublication=2011
|YearOfPublication=2011
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The EGNOS space segment is composed of four geostationary satellites (GEO) broadcasting corrections and integrity information for GPS satellites in the L1 frequency band (1575,42 MHz). The configuration of the GEOs in operation does not change frequently but possible updates are nevertheless reported to users by the EGNOS Service Provider. At the date of publication the 4 GEOs used by EGNOS over time are:
* Inmarsat 3F2 AOR-E | PRN Number 120 | Orbital Slot 15.5 W
* Astra Ses-5 | PRN Number 136 | Orbital Slot 5 E
* Inmarsat 4F2 Emea | PRN Number 126 | Orbital Slot 64 E
* Astra-5B | PRN Number 123 | Orbital Slot 31.5 E
EGNOS GEO satellites SES-5 (PRN 136), ASTRE 5B (PRN 123) and INMARSAT 4F2 EMEA (PRN 126) are currently part of the EGNOS operational platform and are transmitting the operational Signal-In-Space (SIS) to be used by EGNOS users. On 1st January 2019 the INMARSAT 3F2 AOR-E (PRN 120) was decommissioned.<ref name = "EGNOS Service Notice"> [https://egnos-user-support.essp-sas.eu/new_egnos_ops/sites/default/files/documents/service_notice_20_0.pdf EGNOS Service Notice 20]</ref> From 23rd March 2020 onwards, PRN123 and PRN136 are operational while the PRN126 is in test mode.<ref name = "EGNOS Service Notice22"> [https://egnos-user-support.essp-sas.eu/new_egnos_ops/sites/default/files/documents/service_notice_22_0.pdf EGNOS Service Notice 22]</ref>
This space segment configuration provides a high level of redundancy over the whole service area in case of a geostationary satellite link failure. The EGNOS operations are handled in such a way that, at any point in time, at least two GEOs broadcast an operational signal. Since it is only necessary to track a single GEO satellite link to benefit from the EGNOS Services, this secures a switching capability in case of interruption and ensures a high level of continuity of service.
[[File:EGNOS_Coverage.png|Source: EGNOS Service Notice #22 <ref name = "EGNOS Service Notice22"> [https://egnos-user-support.essp-sas.eu/new_egnos_ops/sites/default/files/documents/service_notice_22_0.pdf EGNOS Service Notice 22]</ref>  |340px|thumb|right]]
It is intended that the EGNOS space segment will be replenished over time in order to maintain a similar level of redundancy. The exact orbital location of future satellites may vary, though this will not impact the service offered to users. Similarly, different PRN code numbers may be assigned to future GEOs. The PRN code changes will be explain in the future Service Definition Documents <ref name=" EGNOS Safety of Life Service Definition Document">[https://egnos-user-support.essp-sas.eu/new_egnos_ops/sites/default/files/documents/egnos_sol_sdd_in_force.pdf EGNOS Safety of Life Service Definition Document ]</ref> <ref name=" EGNOS Open Service Service Definition Document">[https://egnos-user-support.essp-sas.eu/new_egnos_ops/sites/default/files/documents/egnos_os_sdd_in_force.pdf EGNOS Open Service Service Definition Document]</ref> and in complementary EGNOS Service Notices.
The foreseen new services will be made available from the provision of new signals from the last EGNOS transponders generation embarked on-board the SES-5 and ASTRA-5B geostationary satellites. Both satellites are capable of transmitting dual-frequency signals compliant with GPS L1/L5 and Galileo E1/E5 signal specifications (GPS L1/L5 and Galileo E1/E5 will be augmented by EGNOS V3 evolution), but L1-only signals were introduced into the EGNOS service provision.<ref>[http://www.gsa.europa.eu/news/gsa-kicks-egnos-geo-transponder-service-contracts GSA Kicks Off EGNOS GEO Transponder Service Contracts], GSA, November 27, 2014</ref>


The EGNOS space segment is composed by three geostationary satellites centred over Europe:


* Inmarsat-3 AOR-E (Atlantic Ocean Region East) stationed at 15.5° W.
* Inmarsat-3 IOR-W (Indian Ocean Region West) stationed at 25.0°E.
* ESA-Artemis stationed at 21.5° E.


The main criteria followed in the selection of the satellites positions have been:
The main criteria followed in the selection of the satellites positions have been:
* Improve the measurement geometry and hence the system availability.
* Improve the measurement geometry and hence the system availability.
* Maximise the visibility angle diversity and hence minimise the risk of signal blocking.
* Maximise the visibility angle diversity and hence minimise the risk of signal blocking.
* Provide dual geostationary coverage (minimum) within the core service area.
* Provide dual geostationary coverage (minimum) within the core service area.


==The Inmarsat-3 Satellite-Navigation Mission==
==The Inmarsat-3 Satellite-Navigation Mission==


Inmarsat’s Third Generation satellites carry a navigation payload which is used by EGNOS.<ref name=" The Inmarsat-3 Satellite Navigation Payload">The Inmarsat-3 Satellite Navigation Payload; George V. Kinal and Oleg Razumovsky, Inmarsat, London </ref>
[[File:Inmarsat-3_Nav_Payload.JPG| Inmarsat-3 Navigation Payload block diagram  |300px|thumb|right]]
 
Inmarsat’s Third Generation satellites carry a navigation payload which is used by EGNOS, as can be seen in the Service Definition Document.<ref name=" EGNOS Open Service Service Definition Document">[https://egnos-user-support.essp-sas.eu/new_egnos_ops/sites/default/files/documents/egnos_os_sdd_in_force.pdf EGNOS Open Service Service Definition Document]</ref>


The first Inmarsat-3 (F2 AOR-E) satellite carrying an EGNOS transponder was launch in September 2006 (PRN 120) while the second one, Inmarsat-3 F5 IOR-W, was launch in February 1998.<ref name=" EGNOS Programme Evolution">[http://egnos-portal.gsa.europa.eu/discover-egnos/programme-information/evolution  EGNOS Programme Evolution (EGNOS Portal) ]</ref>
The first Inmarsat-3 (F2 AOR-E) satellite carrying an EGNOS transponder was launched in September 1996 (PRN 120) while the second one, Inmarsat-3 F5 IOR-W, was launched in February 1998 (PRN 126).


[[File:Inmarsat-3_Nav_Payload.JPG| Inmarsat-3 Navigation Payload block diagram  |300px|thumb|right]]
Inmarsat-3s were built by Lockheed Martin Astro Space (now Lockheed Martin Missiles & Space) of the USA, responsible for the basic spacecraft, and the European Matra Marconi Space (now Astrium), which developed the communications payload, being the first satellite launched by the Proton launch vehicle.<ref name=" Inmarsat Wikipedia Web site">[https://en.wikipedia.org/wiki/Inmarsat  Inmarsat Wikipedia Web site]</ref>
 
On 30th August 2018, the GEO satellite INMARSAT 3F2 (PRN120) became part of the EGNOS TEST Platform broadcasting the TEST SIS. On 1st January 2019, it ceased to broadcast EGNOS SIS and was totally removed from the EGNOS system<ref name=" EGNOS GEO Evolution">[https://egnos-user-support.essp-sas.eu/new_egnos_ops/sites/default/files/documents/service_notice_15.pdf EGNOS Service Notice 15 ]</ref>.
 
==The Inmarsat-4 Satellite-Navigation Mission==
Inmarsat’s Forth Generation satellites carry a navigation payload which is used by EGNOS.
The first Inmarsat-4 (IOR) were built by EDAS Astrium and was launched in 11 March 2005 at orbital position 143, 5º East, using the Atlas V rocket. This satellite was launched with the intention of providing BGAN and GSPS services and also for bands wide rent.
After that, a second satellite (AOR-West) was launched in 8 November 2005 at orbital position 53º West, in order to complement the BGAN and GSPS services aforementioned. The launch was made with a Proton-M/Briz-M rocket.
Finally, the Third phase of Inmarsat-4 was launched in 18 August 2008 at orbital position 98º West, by a Proton rocket. <ref name=" European Geostationary Overlay Service">[https://en.wikipedia.org/wiki/European_Geostationary_Navigation_Overlay_Service European Geostationary Overlay Service ]</ref>


==The ESA Artemis Satellite-Navigation Mission==


[[File:Artemis_Nav_Payload.JPG| The ARTEMIS Navigation Payload: block diagram  |300px|thumb|right]]


The ESA ARTEMIS satellite is not an ordinary telecommunications satellite. It incorporates new, advanced technologies that expand and improve all areas of navigation, mobile communication and satellite-to-satellite communications. Having reached its final orbital position on 31January 2003, ARTEMIS soon began delivering its planned data-relay, land-mobile and navigation services. In particular, its L-band land mobile payload is being used to complement and augment the European Mobile System, its data-relay payloads are being prepared to provide operational services to ENVISAT and SPOT-4, and its navigation payload a major operational element of the European Global Navigation Overlay Service (EGNOS).<ref name=" The ESA ARTEMIS Satellite Navigation Mission">The ESA ARTEMIS Satellite Navigation Mission: In Orbit Testing and use in EGNOS; J. Ventura-Traveset, P.Y. Dussauze, C. Montefusco, F. Toran, ESA GNSS-1 Project Office; C. Lezy , F. Absolonne, B. Demelenne, European Space Agency (ESA), ESA Redu Station; A.Bird; ESA, ARTEMIS Project, ESA ESTEC </ref>
==Astra Ses-5==
Astra SES-5 is a commercial geostationary communication satellite operated by SES. It was launched on 9 July 2012 at orbital position 5º East. The launch was made with a Proton-M/Briz-M rocket from the Baikonur air base in Kazajistan.
It was constructed by Space Systems/Loral, and is based on the LS-1300 satellite bus. The satellite is equipped with 24-C band (36MHz) and 36 Ku-band (33-36MHz) transponders. This satellite was born with the intention of improving the capacity for DTH (Direct to Home) and EGNOS services.
The mission programmed duration is 15 years and the coverage area comprises of Sub-Saharan Africa, North Africa, Europe and Middle East Atlantic Ocean.  


The Artemis navigation payload was introduced at a very late stage of the ARTEMIS satellite development and a very tight schedule was imposed on its procurement. As a consequence and to minimize all possible impacts, it was decided to design it as a completely separated structure, which shall be installed on the spacecraft top floor. Additionally, the payload design and the relevant pieces of equipment were approached, by maximizing the use of already available commercial products and avoiding as much as possible new technologies.


The technical design drivers for the navigation payload were the following:
==Astra-5B==
[[File:Astra-5B.png| Astra-5B coverage  |340px|thumb|right]]
The Astra-5B satellite officially came into service in June 2014 at orbital position 31.5º East. The Astra 5B was launched into space on 22 March 2014. The launch was made with an Ariane 5 rocket from the Kourou air base in French Guiana.
The satellite is equipped with 40 Ku-band transponders (equivalent to 36MHz) and 6 Ka-band transponders. In addition this new transponder will support the next EGNOS generation (EGNOS V3) that will provide dual-frequency signals on both bands L1 and L5 and augment both GPS and Galileo. <ref>[http://www.gsa.europa.eu/news/egnos-capability-and-service-enhanced-addition-new-generation-transponders EGNOS Capability And Service Enhanced With Addition Of New Generation Transponders], ESA, March 2014</ref>
This satellite was born with the intention of improving the capacity for DTH (Direct to Home) services. Also for the capacity of cable services. They also feed digital terrestrial television networks in Central Europe, Eastern Europe and in particular Russia and neighbouring markets. 
The Astra-5B was the 56th satellite in the SES fleet. It has two coverage beams, Wide and High Power. The High Power can be captured in the westernmost part of Europe, as can be seen in the image. <ref name=" Astra-5B High Powder coverage">[http://www.lyngsat-maps.com/footprints/Astra-5B-High-power.html Astra-5B High Power coverage]</ref>


* Appropriate frequency selection for compatibility with other existing missions;
* Good control of the group delay stability;
* Electrical and mechanical constraints imposed by the existing ARTEMIS hardware;
* Maximum reuse of off-the-shelf equipments for minimum schedule risk.


To ensure maximum compatibility with the existing missions it was decided to select for both the uplink and downlink channels the Ku-band, with a new allocation for the uplink and sharing the LLM channels in the downlink. The selection of a widely spaced Ku-band uplink ensures the possibility to use a very high EIRP in the uplink as required for an interference and jammer robust system.


For the second point, it was decided to limit the number of frequency conversion and to avoid the use of SAW filters selecting a channel filtering at Ku-band. Provisions have been taken to calibrate the payload transit time in temperature. Finally, the channel bandwidth has been slightly oversized to avoid the strong group delay variations at the narrowband channel filter edges.


The uplink signal is received at 13.875 GHz by Ku-band feeder link antenna now shared with the LLM payload, and filtered by an input multiplexer which is separating the navigation from the LLM channels. The input multiplexer provides also a first wideband filtering function to reduce interferences.


In the Ku-band receiver the signal is first amplified by a low noise front end and then directly down converted to the Ku-band downlink frequency. In order to maximize the reuse of existing hardware, it has been chosen not to employ a dedicated reference generator for the navigation payload. The same Ultra Stable Oscillator of the LLM payload is used to drive a dedicated frequency generation unit for the required Local Oscillator tones.


The signal is then fed into the narrowband channel filter which is approximately 9 MHZ wide and which is responsible of the principal filtering function of the transponder. The performance of this filter has been specified in order to meet the extremely demanding stability of the payload group delay.


At the output of the channel filter, the signal is fed into the channel amplifier where it is split in two streams. The first, at Ku-band is amplified and fed into the LLM output power stage, while the second is down converted into the GPS L1 frequency (1575.42 MHZ). Normal mode of operation of the channel amplifier is the Automatic Level Control (ALC) mode, which provides a constant output level to the following RF power sections. In ALC mode the navigation payload can provide a stable output level selectable by telecommand, implementing two basic functions:


* Up-link path signal variation recovery.
* L1 channel EIRP selection.


As the EGNOS signal is specified to be transmitted in (right hand) circular polarization, this has been implemented with an output hybrid, which splits the signal into two streams 90° phased apart. These two streams are then driven into the L-band power amplifiers, which are providing 16 W RF e.o.l. with 50 W power consumption, and then fed into the two linear polarization probes of an axially corrugated horn which provides 15 dBi e.o.c. gain.


All units are redounded in order to meet the specified mission probability target of 0.7 of meeting full performance requirements for 10 years on-station life (inclusive of spacecraft). The total mass for the navigation payload, including the structure, the thermal control hardware and the DC harness is 25 kg. Its total power consumption is in the order of 110 W.


==GEO Replenishment options==


The following three options were identified for the EGNOS GEO replenishment:<ref name=" EGNOS GEO Replenishment">EGNOS GEO Replenishment: Planning for the Future; Javier Ventura-Traveset, European Space Agency; Sally Basker, SBAS Limited; Ken Ashton, National Air Traffic Service Ltd. </ref>


# Next Generation of Inmarsat Satellites
# Piggy Back Navigation Payload in a planned GEO multi-mission satellite
# In the context of  integration of EGNOS into Galileo, the implementation  of  GALILEO GEOs providing EGNOS links.


==Notes==
==Notes==
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<references/>
<references/>


[[Category:EGNOS]]
[[Category:EGNOS|Space]]
[[Category:EGNOS Architecture]]
[[Category:EGNOS Architecture|Space]]

Latest revision as of 11:02, 18 March 2020


EGNOSEGNOS
Title EGNOS Space Segment
Edited by GMV
Level Basic
Year of Publication 2011
Logo GMV.png

The EGNOS space segment is composed of four geostationary satellites (GEO) broadcasting corrections and integrity information for GPS satellites in the L1 frequency band (1575,42 MHz). The configuration of the GEOs in operation does not change frequently but possible updates are nevertheless reported to users by the EGNOS Service Provider. At the date of publication the 4 GEOs used by EGNOS over time are:

  • Inmarsat 3F2 AOR-E | PRN Number 120 | Orbital Slot 15.5 W
  • Astra Ses-5 | PRN Number 136 | Orbital Slot 5 E
  • Inmarsat 4F2 Emea | PRN Number 126 | Orbital Slot 64 E
  • Astra-5B | PRN Number 123 | Orbital Slot 31.5 E

EGNOS GEO satellites SES-5 (PRN 136), ASTRE 5B (PRN 123) and INMARSAT 4F2 EMEA (PRN 126) are currently part of the EGNOS operational platform and are transmitting the operational Signal-In-Space (SIS) to be used by EGNOS users. On 1st January 2019 the INMARSAT 3F2 AOR-E (PRN 120) was decommissioned.[1] From 23rd March 2020 onwards, PRN123 and PRN136 are operational while the PRN126 is in test mode.[2]

This space segment configuration provides a high level of redundancy over the whole service area in case of a geostationary satellite link failure. The EGNOS operations are handled in such a way that, at any point in time, at least two GEOs broadcast an operational signal. Since it is only necessary to track a single GEO satellite link to benefit from the EGNOS Services, this secures a switching capability in case of interruption and ensures a high level of continuity of service.

Source: EGNOS Service Notice #22 [2]

It is intended that the EGNOS space segment will be replenished over time in order to maintain a similar level of redundancy. The exact orbital location of future satellites may vary, though this will not impact the service offered to users. Similarly, different PRN code numbers may be assigned to future GEOs. The PRN code changes will be explain in the future Service Definition Documents [3] [4] and in complementary EGNOS Service Notices. The foreseen new services will be made available from the provision of new signals from the last EGNOS transponders generation embarked on-board the SES-5 and ASTRA-5B geostationary satellites. Both satellites are capable of transmitting dual-frequency signals compliant with GPS L1/L5 and Galileo E1/E5 signal specifications (GPS L1/L5 and Galileo E1/E5 will be augmented by EGNOS V3 evolution), but L1-only signals were introduced into the EGNOS service provision.[5]


The main criteria followed in the selection of the satellites positions have been:

  • Improve the measurement geometry and hence the system availability.
  • Maximise the visibility angle diversity and hence minimise the risk of signal blocking.
  • Provide dual geostationary coverage (minimum) within the core service area.


The Inmarsat-3 Satellite-Navigation Mission

Inmarsat-3 Navigation Payload block diagram

Inmarsat’s Third Generation satellites carry a navigation payload which is used by EGNOS, as can be seen in the Service Definition Document.[4]

The first Inmarsat-3 (F2 AOR-E) satellite carrying an EGNOS transponder was launched in September 1996 (PRN 120) while the second one, Inmarsat-3 F5 IOR-W, was launched in February 1998 (PRN 126).

Inmarsat-3s were built by Lockheed Martin Astro Space (now Lockheed Martin Missiles & Space) of the USA, responsible for the basic spacecraft, and the European Matra Marconi Space (now Astrium), which developed the communications payload, being the first satellite launched by the Proton launch vehicle.[6]

On 30th August 2018, the GEO satellite INMARSAT 3F2 (PRN120) became part of the EGNOS TEST Platform broadcasting the TEST SIS. On 1st January 2019, it ceased to broadcast EGNOS SIS and was totally removed from the EGNOS system[7].

The Inmarsat-4 Satellite-Navigation Mission

Inmarsat’s Forth Generation satellites carry a navigation payload which is used by EGNOS. The first Inmarsat-4 (IOR) were built by EDAS Astrium and was launched in 11 March 2005 at orbital position 143, 5º East, using the Atlas V rocket. This satellite was launched with the intention of providing BGAN and GSPS services and also for bands wide rent. After that, a second satellite (AOR-West) was launched in 8 November 2005 at orbital position 53º West, in order to complement the BGAN and GSPS services aforementioned. The launch was made with a Proton-M/Briz-M rocket. Finally, the Third phase of Inmarsat-4 was launched in 18 August 2008 at orbital position 98º West, by a Proton rocket. [8]


Astra Ses-5

Astra SES-5 is a commercial geostationary communication satellite operated by SES. It was launched on 9 July 2012 at orbital position 5º East. The launch was made with a Proton-M/Briz-M rocket from the Baikonur air base in Kazajistan. It was constructed by Space Systems/Loral, and is based on the LS-1300 satellite bus. The satellite is equipped with 24-C band (36MHz) and 36 Ku-band (33-36MHz) transponders. This satellite was born with the intention of improving the capacity for DTH (Direct to Home) and EGNOS services. The mission programmed duration is 15 years and the coverage area comprises of Sub-Saharan Africa, North Africa, Europe and Middle East Atlantic Ocean.


Astra-5B

Astra-5B coverage

The Astra-5B satellite officially came into service in June 2014 at orbital position 31.5º East. The Astra 5B was launched into space on 22 March 2014. The launch was made with an Ariane 5 rocket from the Kourou air base in French Guiana. The satellite is equipped with 40 Ku-band transponders (equivalent to 36MHz) and 6 Ka-band transponders. In addition this new transponder will support the next EGNOS generation (EGNOS V3) that will provide dual-frequency signals on both bands L1 and L5 and augment both GPS and Galileo. [9] This satellite was born with the intention of improving the capacity for DTH (Direct to Home) services. Also for the capacity of cable services. They also feed digital terrestrial television networks in Central Europe, Eastern Europe and in particular Russia and neighbouring markets. The Astra-5B was the 56th satellite in the SES fleet. It has two coverage beams, Wide and High Power. The High Power can be captured in the westernmost part of Europe, as can be seen in the image. [10]








Notes

References

  1. ^ EGNOS Service Notice 20
  2. ^ a b EGNOS Service Notice 22
  3. ^ EGNOS Safety of Life Service Definition Document
  4. ^ a b EGNOS Open Service Service Definition Document
  5. ^ GSA Kicks Off EGNOS GEO Transponder Service Contracts, GSA, November 27, 2014
  6. ^ Inmarsat Wikipedia Web site
  7. ^ EGNOS Service Notice 15
  8. ^ European Geostationary Overlay Service
  9. ^ EGNOS Capability And Service Enhanced With Addition Of New Generation Transponders, ESA, March 2014
  10. ^ Astra-5B High Power coverage
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