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Inmarsat-4A F4

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Title: Inmarsat-4A F4  
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Inmarsat-4A F4

Inmarsat-4A F4
Mission type Communications
Operator Inmarsat
European Space Agency
COSPAR ID 2013-038A
SATCAT № 39215
Mission duration 15 years
Spacecraft properties
Bus Alphabus
Manufacturer EADS Astrium
Thales Alenia Space
Launch mass 6,649 kilograms (14,659 lb)
Start of mission
Launch date 25 July 2013, 19:54:07 (2013-07-25T19:54:07Z) UTC
Rocket Ariane 5ECA VA-214
Launch site Kourou ELA-3
Contractor Arianespace
Orbital parameters
Reference system Geocentric
Regime Geostationary
Longitude 25° east
Perigee 35,771 kilometres (22,227 mi)
Apogee 35,801 kilometres (22,246 mi)
Inclination 0.14 degrees
Period 23.92 hours
Epoch 29 October 2013, 17:07:36 UTC[1]

Inmarsat-4A F4, also known as Alphasat and Inmarsat-XL, is a large geostationary communications satellite operated by UK based Inmarsat in partnership with the European Space Agency. Launched in 2013, it is used to provide mobile communications to Africa and parts of Europe and Asia.[2]

Inmarsat-4A F4 has been constructed by EADS Astrium and Thales Alenia Space based on the Alphabus satellite bus. It was the first Alphabus spacecraft to be launched, and as such it carries several experimental communications systems in addition to its commercial payload. The spacecraft had a launch mass of 6,649 kilograms (14,659 lb), and is expected to operate for at least fifteen years.[2]

Arianespace had been contracted to launch Inmarsat-4A F4, with an Ariane 5ECA rocket, flight number VA-214, delivering it and INSAT-3D into geosynchronous transfer orbit.[3] The rocket lifted off from ELA-3 at Kourou at 19:54:07 UTC on 25 July 2013,[4] with Inmarsat-4A F4 separating from the rocket around 27 minutes later.[5]

The spacecraft operates in a geostationary orbit at a longitude of 25 degrees east. As of 29 October 2013, it is in an orbit with a perigee of 35,771 kilometres (22,227 mi), an apogee of 35,771 kilometres (22,227 mi) and 0.14 degrees inclination to the equator. The orbit had a semimajor axis of 42,157.20 kilometres (26,195.27 mi) and eccentricity of 0.0003552, giving it an orbital period of 1,435.75 minutes, or 23.92 hours.[1]

European Data Relay System test

The satellite was used as part of a in-orbit verification of the ESA European Data Relay System. In 2014, data from the Sentinel-1A satellite in LEO was transmitted via an optical link to the Alphasat in GEO and then relayed to a ground station using a Ka band downlink. The new system can offer speeds up to 7.2 Gbit/s in the future.[6]


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External links

  • EDRS SpaceDataHighway

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