Third Inmarsat-4 satellite set for launch on 19 August 2008

London, Toulouse, Baikonur.- The third Inmarsat-4 satellite, designed and built by Astrium, is scheduled for launch in the night of 18 to 19 August 2008 from Baikonur by an ILS provided Proton Breeze M vehicle.

Three Inmarsat I-4 spacecraft have been built to support Inmarsat’s mobile broadband services, delivering unprecedented voice and broadband data connectivity to users at sea, on land and in the air.

The third giant Inmarsat-4 satellite will be positioned in geostationary orbit at 98° West longitude, enabling Inmarsat to offer global coverage – the two first satellites launched in 2005 are already in operation; all three satellites are identical and interchangeable, their coverage is programmable and can be reconfigured in orbit.

These highly innovative satellites are based on Astrium’s Eurostar E3000 satellite platform, eleven of which have been operational since 2004. All three Inmarsat-4 satellites are equipped with a plasma propulsion system. Their 45m wide solar array generate more than 14 kW of electrical power and the spacecraft weighs nearly 6,000 kg at launch. The main body is 7 metres high and the unfurlable antenna reflector has a surface of about 80 square meters.

In order to support small terminals over the whole area with the high signal strength required, each satellite can digitally form 228 narrow spot beams. More power and spectrum can be allocated to certain beams, further enhancing mission flexibility to cope with the fluctuations in traffic. An on-board digital signal processor designed and built by Astrium, routes the signals to the different beams, acting like a switchboard in the sky: any signal uplink can be routed to any mobile downlink beam and vice versa. Frequency agility and extensive frequency re-use across the beams permit efficient utilisation of the available channels in the L-band spectrum to provide increased capacity.