Alphasat or Inmarsat-4A F4 (originally Alphasat I-XL or Inmarsat XL) is a joint ESA and Inmarsat communications satellite using the Alphabus proto-flight platform, achieving in-orbit validation of the ESA initiated platform through a commercial operator.
Alphasat features a new generation digital signal processor for the payload, and a 12-meter aperture antenna reflector. The spacecraft has a mass of 6649 kg at launch, an electrical power of 12 kW. Planned for launch in 2012, Alphasat has a design lifetime of 15 years.
Inmarsat intends to fly an extended L- band payload, in parallel to and supporting its existing world-leading global mobile satellite services. This Inmarsat mission definition is based around multimedia mobile services already provided by the current Inmarsat-4 satellites through Broadband Global Area Network (GAN)
The satellite is positioned at 25 degrees east, with its coverage centred over Africa and providing additional coverage to Europe, the Middle-East and parts of Asia.
Implementation of this Geo-mobile application uses the Alphabus platform design in a configuration that requires a 90 degree change to the satellite flight orientation to improve accommodation of the feed/reflector configuration and allow the embarkation of a large deployable reflector. Both of these capabilities are offered as options in the Alphabus portfolio.
In addition, Alphasat embarks three ESA-provided technology demonstration payloads:
The Alphasat programme meets the diverse but mutually compatible goals of all the parties, such as the first flight and in-orbit verification of Alphabus and the implementation of an advanced L-band operational payload, which supplements the existing Inmarsat satellite constellation and offer the opportunity for new and advanced services.
The contract was signed in November 2007 with a launch targeted by 2013.
|Type / Application:||Communication|
|Contractors:||EADS Astrium, Thales Alenia Space|
|Propulsion:||EAM, PPS-1350-G plasma thrusters|
|Power:||2 deployable solar arrays, batteries|
|Alphasat (Inmarsat-4A F4)||25.07.2013||Ko ELA-3||Ariane-5ECA||with Insat 3D|