UPDATED Sept. 22 at 10:14 a.m. EDT

PARIS — The company that sells Russian Proton heavy-lift rockets on the commercial market expects to be able to conduct four or five more commercial missions before the end of 2011 despite the year’s slow start due to late-arriving satellites and a mid-August failure of the rocket it uses.

The Proton rocket returned to flight Sept. 21, carrying a Russian military satellite into orbit, according to the Russian space agency, Roscosmos. By the end of the year the vehicle is scheduled to launch four or five more commercial missions and three Russian government missions.

Before the August failure, in which a $300 million Russian government telecommunications satellite was placed into a useless orbit, Proton had been scheduled to make 12 flights this year.

Reston, Va.-based International Launch Services (ILS), which has conducted two successful commercial launches so far in 2011 — the August failure was a Russian government mission not operated by ILS — is bracing for a gradual market downturn that the company has long forecasted for commercial satellites.

In a press briefing and presentation here during the World Satellite Business Week conference organized by Euroconsult June 13-17, ILS President Frank McKenna said his company has booked seven commercial contracts so far in 2011. These include one with an unidentified customer for a launch in late 2012 and an option for a second launch.

ILS officials said the customer was not Spacecom of Israel, whose Amos 4 satellite is expected to launch around that time aboard an unidentified rocket.

ILS’s seven contract wins this year compare with nine commercial flights booked by the Arianespace consortium of Evry, France, and one flight by Sea Launch of Bern, Switzerland, which was expected to return to flight Sept. 25 from its floating platform in the Pacific Ocean.

McKenna said that taking the global commercial launch industry as a whole, there will likely be no more than 22 or 23 contracts signed in 2011, a significant drop from the approximately 30 contracts signed in each of the past two years.

Commercial satellite builders have reported similar figures, saying commercial satellite construction contracts in 2011, which have totaled no more than a dozen, are likely to climb to around 18 by the end of the year.

There is often a lag of several months from the time a satellite construction contract is signed to when the launch of the satellite is ordered.

McKenna and ILS have been among the most bearish in the market in warning about the coming downturn, generally attributed to the end of the most recent fleet replenishment and expansion cycle among the largest commercial satellite operators.

McKenna said the coming market decline is starting to be felt in the form of downward pressure on launch prices. “What we have predicted is coming true and you will see it even more clearly as we move toward 2013,” McKenna said. He said the return of Sea Launch to the market also is having an effect on prices for heavier satellites, which is the specialty of Sea Launch and ILS.

Sea Launch President Kjell Karlsen confirmed in a Sept. 12 interview that prices have declined recently.

Launch prices for smaller telecommunications satellites also have dipped, McKenna said, because Arianespace is responding to the presence of startup launch provider Space Exploration Technologies (SpaceX) of Hawthorne, Calif., which has advertised prices far lower than the current commercial competition.

Arianespace Chief Executive Jean-Yves Le Gall disputed this, saying Sept. 13 that his company, whose Ariane 5 ECA heavy-lift rocket has booked 45 consecutive successes since 2003, is not lowering prices. Le Gall said the Ariane 5 record enables customers to get insurance rates that are lower than premiums demanded for competing launch service providers and is one reason Arianespace has not been forced to reduce its rates.

McKenna said the August Proton failure, attributed to an erroneous software program loaded onto the rocket’s computer, is thoroughly understood by Proton’s builders, with corrective measures added.

McKenna said that while the failure was of a government mission unaffiliated with ILS, the U.S. company has made its customers fully aware of the failure review board conclusions.

“We’re operating with as much transparency as we would use if it were our own mission that failed,” McKenna said. “We have had tremendous cooperation from Roscosmos in terms of dissemination of technical information and the processing of needed licenses for the briefing of insurance underwriters.”

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