Inmarsat-4: the power behind BGAN

The first three Inmarsat-4 (I-4) satellites were launched into geostationary orbit between 2005-8. They were built by an international team of space technologists from the United Kingdom, France, Germany, the USA and Canada, with European satellite manufacturer EADS Astrium as the lead contractor.

Based on the Eurosat E3000 spacecraft bus, these first I-4s had a mass of 5.96 tonnes at launch and were designed to have a service life of 13 years. Each can generate up to 19 wide beams and more than 200 narrow spot beams.

Satellite resources

When required, for example in the wake of a natural disaster, satellite resources can quickly be reconfigured to provide extra capacity where needed.

The spacecraft’s other impressive features include:

  • The I-4 body – approaching the size of a double-decker bus at 7m x 2.9m x 2.3m
  • Solar arrays – with a wing span of 45 metres they extend almost the width of a soccer pitch
  • Solar panels – combining conventional silicon with advanced gallium arsenide (GaAs) cells for optimum efficiency
  • Digital signal processor – controlling the antennas, beam forming and channel allocation
  • Reflector – Nine metres wide and designed to unfurl in orbit like a giant flower
  • Antennas – 120 helix elements combined in a single flexible array
  • Thrusters – both chemical and plasma ion for orbital station keeping.

In 2010, the I-4 satellite won the Royal Academy of Engineering’s prestigious MacRobert Award for innovation for making possible the world’s first planet-wide 3G mobile communications network – Inmarsat’s Broadband Global Area Network (BGAN).

Alphasat (Inmarsat I-4A F4) joins the fleet

With the launch of Alphasat, Inmarsat becomes the commercial operator of one of the most technically advanced satellites for civilian applications.

Alphasat is the largest European telecommunications satellite ever built, with a total mass of more than 6.6 tonnes at launch. It supplements Inmarsat’s existing I-4 series, providing coverage over Europe, the Middle East and Africa from its in-orbit location at 25 degrees East.

Alphasat brings new capabilities to the Inmarsat fleet in terms of performance and resource availability, including 50 per cent more accessible L-band spectrum and nearly 20 per cent more mobile communication channels.

Additional capacity

With a nominal operational lifespan of 15 years, it will provide additional capacity to handle more than 750 communication channels with improved quality, particularly for satellite phone users.

It will also enable Inmarsat to:

  • Introduce new products and services over key land mass areas
  • Develop new high-data rate (HDR) services for new and existing customers, such as broadcast media
  • Provide additional capacity in areas with the highest levels of traffic
  • Support maritime and aviation communities with improved safety of life applications and a new range of safety services.

Our US$350 million investment in Alphasat – as part of Europe’s largest public-private partnership space project – demonstrates Inmarsat’s long-term commitment to offering services in the L-band, a robust and reliable portion of the radio spectrum largely unaffected by poor weather conditions.

Joint contract with ESA

The spacecraft platform, Alphabus, was developed by Astrium and Thales Alenia Space under a joint contract with the European Space Agency (ESA) and Centre National d’Études Spatiales (CNES).

Alphasat’s communications payload, including the advanced digital processor which doubles the spectrum efficiency of the standard I-4 satellites, was designed and built at Astrium’s UK plants in Stevenage and Portsmouth, with important contributions from Astrium in France and Germany.

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