PARIS — Mobile satellite services provider Inmarsat is asking prospective satellite builders to study a fifth-generation Inmarsat constellation that would carry a mixed L- and Ka-band payload to provide broadband links to maritime and other mobile platforms, according to industry officials.

London-based Inmarsat, which has built a profitable business providing medium-speed L-band data and voice links to mobile users, is apparently readying itself for what would be a major switch as Ka-band satellites with many times the throughput of today’s spacecraft prepare to enter the market.

Industry officials said Inmarsat is unlikely to make a near-term commitment of the necessary resources — ultimately, $2 billion or so — to build a fleet of three or four satellites with a mixed Ka-band and L-band payload. The company has been selling itself to investors as the sole mobile satellite operator that has no immediate need to make a substantial capital investment.

The three Inmarsat-4 satellites that now provide most of Inmarsat’s revenue were launched between 2005 and 2008. All are healthy and expected to operate for 15 years.

In addition, Inmarsat is spending around $400 million on a large satellite called Alphasat 1-XL, to provide backup for the Inmarsat-4 fleet. Alphasat, which will also carry experimental telecommunications payloads for European governments that have helped finance the program, is scheduled for launch in 2012.

One industry official said Inmarsat is struggling to determine how far and how quickly demand for broadband access will penetrate its core maritime market. Ka-band presents challenges including signal deterioration in heavy rain when compared with transmissions in the more traditional C-, Ku- and L-band frequencies. But it has the advantage of being much less used than the other frequencies, permitting operators to design satellites with throughputs that are many times what conventional satellites can offer.

Inmarsat spokesman Christopher McLaughlin declined to comment on the company’s request for information from satellite manufacturers, saying only: “We are looking at all options for our future growth, but no decisions have been made.”


Peter B. de Selding was the Paris bureau chief for SpaceNews.