Inmarsat Still Trying To Find Orbital Slots for Global Xpress
LONDON — Mobile satellite services providerhas yet to select the orbital slots for its three Ka-band mobile broadband satellites to be launched starting in 2013 as it contends with a forest of paper satellite applications filed with international regulators for similar satellites, Inmarsat’s Ka-band project manager said Sept. 16.
While the vast majority of competitors’ applications with the International Telecommunication Union (ITU) are for systems that will never be built, the mere fact of submitting an application to the Geneva-based ITU is enough to throw obstacles in Inmarsat’s path.
Ultimately, London-based Inmarsat may resort to co-locating its three Global Xpress satellites at the same orbital position occupied by existing Inmarsat-3 spacecraft, whose primary coverage is over the world’s oceans, according to Leo Mondale, managing director for Global Xpress.
In a Sept. 16 presentation here to the VSAT 2010 conference, Mondale said the orbit over North America is particularly crowded with Ka-band satellite applications — some of which are for real projects — but that the ITU register is littered with applications for Ka-band slots just about everywhere along the geostationary arc 36,000 kilometers over the equator.
“There are increasingly difficult coordination decisions,” Mondale said of the effort to find slots and frequencies, even in the relatively little-used Ka-band, for satellites without violating the rights of others who have filed ITU notifications for systems of varying degrees of credibility.
“The game is to file for all the slots you can, and then pick the ones you want,” Mondale said, conceding that Inmarsat was obliged to do the same thing.
Hughes Communications of Germantown, Md., faced the same issue looking for a slot for its Spaceway 3 Ka-band satellite and eventually was forced to pay a monthly fee to a company that had rights to the slot Hughes wanted but had demonstrated no plans to build and operate a satellite system.
Inmarsat has hired Boeing Satellite Systems International of El Segundo, Calif., to build at least three satellites, and begin work on a fourth, for the $1.2 billion Global Xpress system. Each satellite will carry 89 fixed beams plus six steerable high-capacity overlay (HCO) beams to concentrate bandwidth on small areas.
Industry officials said the spacecraft will use both the civil and military sections of Ka-band. In addition to building the satellites, Boeing has agreed to purchase 10 percent of the system’s capacity for the first five years of Global Xpress operations and plans to sell most of it to the U.S. Defense Department.
Mondale said the HCO feature allows Global Xpress to overcome a limitation of satellites without full digital signal processing, namely that coverage areas are largely fixed before launch.
The three satellites’ 18 HCO beams will have an aggregate bandwidth of 17 gigahertz and permit Ka-band transponders to be allocated according to “unplanned and high-capacity events” such as military operations, Mondale said in his |presentation.
Traffic handled by an HCO beam could be uploaded to the satellite and then downlinked somewhere else within the beam, or to another HCO beam, or sent to one of three planned Global Xpress ground gateways, likely to be located in the western portions of the United States, Europe and Australia, according to Inmarsat.
Depending on the application, military users of the HCO service will be able to connect with 40-centimeter antennas, compared with the 60-centimeter antenna Inmarsat says will be needed for the service on the global beams.
Global Xpress will target land and aeronautical mobile-broadband markets, but the maritime market appears to be a principal focus. Industry competitors, including large satellite fleet operatorsand , have said they too are assembling a global maritime mobile-broadband capacity but will use more-conventional Ku-band, which is less sensitive to rain.
Mondale said Global Xpress has been designed with rain in mind and will have enough power and bandwidth margin to deliver the promised 50 megabits per second in downlink and 5 megabits per second in uplink to the 40- and 60-centimeter user antennas.
“We are not designing to the bleeding edge of satellite technology and then hoping it doesn’t rain,” Mondale said. “We have a design that … will perform as well as Ku-band in rain environments.”
Inmarsat is pitching Global Xpress to maritime customers who, for the most part, already will have Inmarsat L-band antennas on their vessels. The L-band systems will be a natural backup for Global Xpress if a ship encounters conditions that would overwhelm Ka- or Ku-band, he said.