Inmarsat-4A F4

From Wikipedia, the free encyclopedia
Jump to: navigation, search
Inmarsat-4A F4
Alphasat bourget YC2.jpg
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 (2013-07-25UTC19:54:07Z) 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 British geostationary communications satellite operated by 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 was 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 mass at launch of 6,649 kilograms (14,659 lb), and was expected to operate for at least fifteen years.[2]

Arianespace were 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 was 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[edit]

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]


  1. ^ a b "ALPHASAT (INMARSAT 4A-F4) Satellite details 2013-038A NORAD 39215". N2YO. 29 October 2013. Retrieved 29 October 2013. 
  2. ^ a b "Alphasat (Inmarsat-4A F4)". Gunter's Space Page. Retrieved 29 October 2013.  |first1= missing |last1= in Authors list (help)
  3. ^ Bergin, Chris (25 July 2013). "Ariane 5 ECA successfully deploys Alphasat and Insat-3D". Retrieved 29 October 2013. 
  4. ^ McDowell, Jonathan. "Launch Log". Jonathan's Space Page. Retrieved 29 October 2013. 
  5. ^ Clark, Stephen (25 July 2013). "Mission Status Center". Ariane Launch Report. Spaceflight Now. Retrieved 29 October 2013. 
  6. ^ "Laser link offers high-speed delivery". ESA. 28 November 2014. Retrieved 5 December 2014. 

External links[edit]