LE BOURGET, France — Inmarsat expects to sign parallel contracts with a European industry team and the European Space Agency (ESA) by September for delivery of a large geostationary-orbiting mobile communications satellite that will test new technologies and a new satellite platform, Inmarsat and ESA officials said.

Inmarsat’s I-XL satellite will be the first in-orbit validation of the ESA-financed Alphabus platform, designed to give European contractors a new product for international satellite competitions. With more power, fewer export-controlled U.S. parts and a new-generation digital signal processor, the I-XL satellite will be used by London-based Inmarsat to extend its high-speed mobile communications service, called BGAN, or Broadband Global Area Network.

The I-XL satellite, to be operated at 25 degrees east longitude, will provide Inmarsat an additional 7 megahertz of L-band spectrum, for both uplink and downlink, besides adding capacity to Inmarsat’s current fleet.

MagaliVaissiere, head of ESA’stelecommunications department, said there appear to be no special hurdles that would prevent a contract with Inmarsat from being signed by September.

Franco Carnevale, Inmarsat’s program manager, said the company expects to sign a related contract with Astrium Satellites for delivery of the completed satellite, also by September.

said June 21 that the Alphabus satellite platform, being built by Astrium and ThalesAlenia Space with financing from

ESA and the French space agency, CNES,

is on schedule for delivery to Inmarsat by late 2011.

He said the satellite will weigh between 6,000 and 6,500 kilograms at launch, depending on the launch vehicle selected and thus the amount of fuel they can load into the satellite’s tanks.

and Vaissiere said the arrangement between the parties includes some of the same penalty clauses for late delivery that are featured in conventional commercial contracts.

“In this case I don’t think the Alphabus platform is the item facing the most challenging schedule,” Carnevale said. “It is probably the DSP [digital signal processor] that we plan to fly, which takes the technology beyond what we have on the Inmarsat-4 satellites.”

The signal processor for the I-XL mission is being provided to Inmarsat under a separate contract with Astrium, which supplied – after considerable development difficulty that delayed the program – the processors for

the two Inmarsat-4 satellites in orbit. A third Inmarsat-4 satellite is assembled and awaiting launch.

Giuseppe Viriglio, ESA’s director of telecommunications,

said one of the ESA-financed payloads on this satellite, a laser communications payload, is designed to provide optical links with the German TanDem-X radar observation satellite in low Earth orbit. The TanDem-X schedule makes it all the more important to have I-XL in orbit soon after its planned delivery in the third quarter of 2011, Viriglio said.

-X is scheduled for launch in 2009 on a five-year mission.

Gene Jilg, Inmarsat’s chief technical officer, said Inmarsat will have a free hand in selecting an I-XL launch vehicle. Inmarsat is responsible for the launch and insurance of the satellite, but since the

mission is partly funded by ESA there is likely to be pressure to use the ESA-developed Ariane 5 rocket.