To install click the Add extension button. That's it.

The source code for the WIKI 2 extension is being checked by specialists of the Mozilla Foundation, Google, and Apple. You could also do it yourself at any point in time.

Kelly Slayton
Congratulations on this excellent venture… what a great idea!
Alexander Grigorievskiy
I use WIKI 2 every day and almost forgot how the original Wikipedia looks like.
Live Statistics
English Articles
Improved in 24 Hours
Added in 24 Hours
What we do. Every page goes through several hundred of perfecting techniques; in live mode. Quite the same Wikipedia. Just better.

Inmarsat-4A F4

From Wikipedia, the free encyclopedia

Inmarsat-4A F4
Alphasat bourget YC2.jpg
Full scale mockup Alphasat at Le Bourget Airshow 2013
Mission typeCommunications
European Space Agency
COSPAR ID2013-038A
SATCAT no.39215
Mission durationExpected: 15 years
Elapsed: 7 years, 11 months, 17 days
Spacecraft properties
ManufacturerEADS Astrium
Thales Alenia Space
Launch mass6,649 kilograms (14,659 lb)
Start of mission
Launch date25 July 2013, 19:54:07 (2013-07-25UTC19:54:07Z) UTC
RocketAriane 5ECA VA-214
Launch siteKourou ELA-3
Orbital parameters
Reference systemGeocentric
Longitude25° east
Perigee altitude35,771 kilometres (22,227 mi)
Apogee altitude35,801 kilometres (22,246 mi)
Inclination0.14 degrees
Period23.92 hours
Epoch29 October 2013, 17:07:36 UTC[1]

Inmarsat-4A F4, also known as Alphasat and Inmarsat-XL, is a large geostationary communications I-4 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]

YouTube Encyclopedic

  • 1/5
    614 388
    21 816
    3 372
  • Inmarsat-5 Flight 4 Launch Webcast
  • Space X Falcon 9 - Inmarsat 5 F4 (Flight 4) Liftoff
  • Alphasat: Technology demonstration
  • Alphasat, the fourth satellite to join Inmarsat's I-4 fleet.
  • Alphasat: new partnership in SatCom


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]


  1. ^ a b "ALPHASAT (INMARSAT 4A-F4) Satellite details 2013-038A NORAD 39215". N2YO. 29 October 2013. Retrieved 29 October 2013.
  2. ^ a b Krebs, Gunter. "Alphasat (Inmarsat-4A F4)". Gunter's Space Page. Retrieved 29 October 2013.
  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

This page was last edited on 23 January 2021, at 09:56
Basis of this page is in Wikipedia. Text is available under the CC BY-SA 3.0 Unported License. Non-text media are available under their specified licenses. Wikipedia® is a registered trademark of the Wikimedia Foundation, Inc. WIKI 2 is an independent company and has no affiliation with Wikimedia Foundation.