PARIS — Eutelsat Chief Executive Michel de Rosen on Nov. 24 said he remains confident that investigators will find the cause of the propulsion system failure on Eutelsat’s W3B telecommunications satellite. But he conceded that one month after the failure, the inquiry is still searching for a smoking gun.

“We are lucky in the sense that, unlike some other satellite failures, we have been able to isolate the problem in the propulsion system,” de Rosen said here during the Space Perspectives 2011 conference organized by Euroconsult and the French aerospace industries association, GIFAS.

“The chief technical officer of Eutelsat is on the board of inquiry, as is the chief technical officer of Thales Alenia Space, the manufacturer. The board also includes the presence of Astrium, the builder of the propulsion system, and of Arianespace, the launch services provider, to provide [launch] metrics,” he said. “I do believe there will be a clear explanation, but we need to let them work a little longer.”

W3B developed a leak in its oxidizer tank that became so serious in the minutes after launch that the satellite could neither be raised into a proper retirement orbit nor be sent on a guided descent into the Pacific Ocean. It is expected to spend several decades in the same highly elliptical transfer orbit in which it was left following separation from the Ariane 5 ECA rocket after launch.

In an interview, de Rosen said he has heard too many theories about what may have happened to W3B to believe any of them at this point. “We have got very good people on this board of inquiry and I will let them reach their conclusions,” he said.

Eutelsat is expected to receive a W3B total-loss insurance payment of about 245 million euros ($333 million) and is expected to sign a contract for a replacement satellite in the coming weeks. Whether Eutelsat will seek a new procurement with competitive bids, or ask Thales Alenia Space to provide a W3B twin, is not known.

Paris-based Eutelsat has asked Thales Alenia Space to speed production, to the extent possible, of the similar W3C satellite that is scheduled for launch in 2011 aboard a Chinese Long March rocket.

Eutelsat, which is the world’s third-largest commercial satellite fleet operator when ranked by revenue and also one of the industry’s most profitable companies, is scheduled to launch its first all-Ka-band broadband satellite in mid-December aboard an International Launch Services Proton rocket from Russia’s Baikonur Cosmodrome in Kazakhstan.

During the conference, de Rosen and Ferdinand Kayser, chief executive of the SES Astra division of fleet operator SES of Luxembourg, debated whether Eutelsat has made a gamble with Ka-Sat that it may regret.

“Questions remain open on Ka-band,” Kayser said in outlining why SES, which is using conventional Ku-band for its European consumer broadband service, has declined to build its own Ka-band satellite. Ka-band’s principal advantage over Ku-band is that, being little used, there is much more bandwidth available for the moment. Eutelsat’s Ka-Sat will generate some 70 gigabits per second of throughput.

“We are in the business of operating satellites that last for 15 years in orbit,” Kayser said. “We must be able to prove to our shareholders that these will be profitable each time we launch. We have been more prudent, or less courageous perhaps, than our competitor Eutelsat.”

De Rosen retorted immediately: “That’s interesting, we think it’s you who are the most audacious, or courageous, by investing in a Ka-band constellation. It’s called O3B is it not?”

O3B is a startup operator based in Britain’s Channel Islands that is planning a constellation of 20 medium-orbit satellites delivering Ka-band to telecommunications operators and corporate networks in the developing world. The company, now managed by SES’s former chief financial officer, Mark Rigolle, is said to be close to closing a financial package of $1.1 billion to build and launch the satellites with the backing of France’s export-credit agency, Coface.

SES has distributed Ka-band capacity over several of its satellites now in construction and has said it is ready to switch its consumer broadband service to Ka-band when necessary. But it has declined to take the risk of a large, all-Ka-band spacecraft.

Once Ka-Sat is launched and in operation, de Rosen said, Eutelsat will proceed cautiously with commercialization with its 68 distribution partners throughout Europe. He declined to say how heavily the Ka-Sat business model will lean on prospective military sales, including Ka-band links to high-altitude, long-endurance unmanned aerial vehicles, but conceded that this is part of the business plan.

Eutelsat, de Rosen said, will let Ka-Sat operate for about a year before deciding whether to order a backup Ka-band satellite.

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