Inmarsat's board approved plans at the beginning of this month to develop a $1.4 billion fourth-generation satellite system. Requests for proposals for the new system, which will be in service by the end of 2004, are due to be issued this month.

The space segment will comprise two in-orbit satellites, plus one ground spare, with the satellites located at 54°W and 64°E. The Inmarsat-4s will be operated with the existing Inmarsat-3s to provide global coverage.

The -4s will be designed to provide personal multimedia communications (PMC) at 144- 432kbits/s - higher data speeds than those of the Inmarsat-3s.

The satellites' 200 narrow spot beams will support the higher 432kbits/s with a signal strength of 67dBW. The 19 overlay wide spot beams will provide 56dBW and the global beam will transmit 39dBW. The spacecraft will operate in Inmarsat's mobile satellite services L-band allocation in the 1.5/1.6GHz band.

Inmarsat's PMC offerings will include portable, lightweight, Internet-ready satellite modem units for use with a mobile notebook computer for multimedia communications services. The international mobile satellite system operator says applications will include Internet-based e-business solutions, on-line content-based services, video conferencing and voice telephony.

The services will be compatible with third-generation cellular systems and will provide a satellite overlay for terrestrial international mobile telecommunications networks.

Source: Flight International