The three Inmarsat-4 satellites, built by Astrium, have been designed to deliver Inmarsat’s Broadband Global Area Network (BGAN) service for seamless mobile voice and broadband Internet connectivity around the world. By providing telephony, data and high speed Internet access to laptop and palm-sized terminals, they enable business travellers, disaster relief workers, field based oil researchers, journalists, etc to operate a virtual office anywhere in the satellite footprint, including on maritime or air routes.
Each satellite can digitally form more than 200 spot beams. More power and spectrum can be allocated to certain beams to cope with the fluctuations in traffic. An on-board digital signal processor 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.
All three satellites are identical and interchangeable – their coverage is programmable and can be reconfigured in orbit. They are based on the E3000 version of Astrium's outstandly successful Eurostar satellite platform series, and equipped with electric propulsion system. Their 45m-long solar array generates 14 kW of electrical power at beginning of life and the spacecraft weighs approximately 5,950 kg at launch. The main body is 7 metres high and the unfurlable antenna reflector has a diameter of about 10 metres.
Astrium is prime contractor for both platform and payload of all the Inmarsat-4 satellites. The first Inmarsat-4 satellite was launched in March 2005 and the second in November 2005. Both are now operational. The third satellite is complete and currently stored on ground.
