PARIS — The U.S. company that markets Russia’s Proton heavy-lift rocket says it can launch Europe’s Galileo satellites for one-third the cost of what the European Commission has agreed to pay to launch the navigation craft aboard the European version of Russia’s Soyuz rocket.

Reston, Va.-based International Launch Services (ILS) is weighing whether to pitch its Proton offer to the commission as part of a broader strategy that includes adapting the rocket to carry two mid-size telecommunications satellites into geostationary-transfer orbit at the same time.

ILS President Frank McKenna said that on a per-kilogram basis, ILS is able to offer owners of smaller telecommunications satellites a 20 percent savings over launches as solo passengers on the European Soyuz or as co-passengers on Europe’s heavy-lift Ariane 5 rocket, both of which are operated by Europe’s Arianespace launch consortium.

In a Jan. 13 interview, McKenna said ILS, which has not been shy about going after contracts that were considered a shoo-in for Arianespace, committed an error in not making an aggressive Proton offer for the Galileo work.

“We miscalculated by not taking this on,” McKenna said. “We saw protectionist policies being put into place” for Galileo, leading ILS to conclude that a closely matched price competition would automatically turn in Arianespace’s favor.

That was before the commission announced Jan. 7 that it has agreed to pay 79.4 million euros, or some $114 million, per launch. The deal calls for five Soyuz launches, each carrying two Galileo satellites.

“Amazingly, a dedicated Proton launch has become competitive with a Soyuz launch,” McKenna said. “We can offer a three-fold decrease” in launch costs per Galileo satellite by using Proton rockets to carry six Galileo spacecraft at a time.

McKenna declined to discuss prices, but one industry official said that while ILS has increased some of its prices in recent months, dedicated Proton launches today are selling for less than $110 million. This official added that Proton would need special payload adapters and dispensers to carry six Galileo satellites, and that these would add to the cost.

“I think the commission can eat its cake and have it, too,” McKenna said, adding that European government authorities also could use the Proton offer as a backup for Soyuz.

European Commission officials would have had trouble accepting an ILS bid because of a declared policy that all Galileo launches should occur from European territory — a policy similar to the one the U.S. government follows for its satellites. Russia’s Soyuz rocket is being modified for use at Europe’s Guiana Space Center spaceport in French Guiana and is scheduled to make its inaugural flight from there in mid-2010.

The five Soyuz launches of Galileo satellites agreed to so far are scheduled to occur at three-month intervals beginning in late 2012.

The commission has said it wants to have at least two vehicles in the Galileo launcher mix to reduce risk. It has negotiated firm prices, but as yet has agreed to no contracts, for Ariane 5 rockets. Arianespace’s Ariane 5 offer for Galileo involves carrying four Galileo satellites per launch.

To launch Galileo, the Ariane 5 ES variant will need to undergo modifications to its upper stage that are expected to cost about 50 million euros.

McKenna said ILS’s new commercial posture is a result of two factors: the Russian ruble’s decline against the U.S. dollar and the euro, and the reorganization of Proton rocket production under the management of ILS’s owner, Khrunichev State Research and Production Space Center of Moscow.

Over the past 18 months, the ruble has moved up and down, sometimes dramatically, with a sharp downward trend in early 2009 that enabled ILS to reduce prices and win customers. As of Jan. 7, 100 rubles were valued at $3.30, down about 19 percent from two years earlier.

The resulting upward trend in prices for Soyuz rockets launched from Europe’s spaceport, when measured in U.S. dollars, has led some telecommunications satellite owners to ask ILS to consider a Proton configuration in which two mid-size satellites are launched into geostationary transfer orbit on a single mission.

ILS and Orbital Sciences Corp. of Dulles, Va., have been working on what they call an ILS/Proton Duo design that would carry two Orbital-built spacecraft. Orbital Chief Executive David W. Thompson said in a Jan. 12 interview that the company is ready to invest in the development of Proton Duo, once a customer has been found, as a way of offering satellite owners a broader choice of launchers beyond Ariane 5 and Soyuz.

Proton has long been used to launch three Russian Glonass navigation and timing satellites at a time into medium Earth orbit, and it has also launched two Russian-built satellites into geostationary orbit in a single mission.

McKenna said ILS and Orbital are already offering Proton Duo launches to customers, and that a first launch — once a pairing of two owners of Orbital-built satellites has been found — could be conducted in 2012.

He said ILS plans a 2011 launch of an Orbital-built satellite paired with the Khrunichev-built KazSat-2 telecommunications satellite under construction for the government of Kazakhstan.

Five of the ILS contracts signed in 2009 were for satellites weighing less than 4,000 kilograms. Orbital’s commercial telecommunications satellite products typically weigh 3,200 kilograms or less.

“What we are doing is diversifying — creating more opportunities for that end of the market in response to customers who have requested us to compete,” McKenna said.

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