PARIS — Satellite fleet operator Satmex said it remains confident that a Russian Proton rocket will launch its Satmex 8 satellite by December, giving the company sufficient time to transfer customers to it before Satmex 5, which the new spacecraft is replacing, runs out of fuel as early as late February.

Satmex said the Aug. 7 failure of the Proton Breeze M rocket, the same vehicle slated to carry Satmex 8, will delay the Satmex 8 launch beyond its scheduled October date. But the company also noted that Russian managers in the past have proved able to return the launcher to flight in short order after failures.

In an Aug. 23 conference call with investors, Satmex Chief Executive Patricio Northland said Proton launch services provider International Launch Services (ILS) has set no new launch date for Satmex 8. But he said the October slot looks lost as ILS and Proton prime contractor and ILS owner Khrunichev Space Center of Moscow, along with the Russian government, work to determine the cause of a problem with the rocket’s Breeze M upper stage.

Russian and Indonesian telecommunications satellites were placed into useless orbits because of the Aug. 7 Breeze M anomaly. Khrunichev and ILS have grounded the Proton pending the results of a failure review inquiry.

Satmex 5 operates at 116.8 degrees west in geostationary orbit. Under a worst-case scenario Satmex presented to investors, the satellite would run out of fuel and be placed into inclined orbit at the end of February.

Inclined-orbit satellites preserve their remaining fuel by no longer using on-board thrusters to stabilize themselves on the north-south axis. Such satellites can continue operating for years, but they are not suitable for many broadcast applications whose user antennas are stationary and depend on a satellite remaining in a fixed position.

The Satmex 8 construction and launch program has always been of concern to Satmex. If there is a gap between Satmex 5’s partial retirement and the in-service availability of Satmex 8, the company is at risk of losing customers that cannot tolerate a service outage.

Satmex earlier had trouble winning investor approval of the Satmex 8 expenditure, and when it secured the needed funds it insisted that manufacturer Space Systems/Loral (SS/L) of Palo Alto, Calif., respect a delivery date consistent with a launch between August and October.

Northland said SS/L has completed Satmex 8 construction and is now awaiting word from Satmex on when to attach the broadcast antennas and solar arrays to prepare for shipping the spacecraft to Russia’s Baikonur Cosmodrome spaceport in Kazakhstan.

Before the Aug. 7 failure, Satmex 8 had been in third position among upcoming launches for Reston, Va.-based ILS. First in line are satellites owned by fleet operators Intelsat and EchoStar. Northland said it would take only two weeks to transfer Satmex 5 customers to Satmex 8 once the latter satellite is declared operational. He did not say how many weeks it would take from the time Satmex 8 is launched until it is likely to be ready for service after in-orbit testing.

Satmex said its estimate of when Satmex 5 will need to be placed into inclined orbit to conserve fuel is a worst-case scenario. The satellite is more likely to continue operating in a fully stabilized position through May, the company said.

Estimating a satellite’s future fuel use and the exact amount of propellant in its tanks remains an art as much as a science. Many operators tend to take satellites out of service earlier than necessary to ensure there is enough fuel to place them into retirement orbits several hundred kilometers above the geostationary arc, which is about 36,000 kilometers above the equator.

Satmex 5’s 24 C-band transponders are nearly 100 percent filled with customers. Its 24 Ku-band transponders are more than 90 percent occupied, on average, the company said in its Aug. 23 presentation.

Satmex 8 will carry 24 C-band transponders and 40 in Ku-band, giving Satmex capacity to grow its business. Loading all Satmex 5 customers onto Satmex 8 will fill only 72 percent of Satmex 8’s capacity, Northland said.

The company now estimates that its Satmex 8 program, including construction, launch and insurance through the first year in orbit, will cost $318 million, compared with earlier estimates of $333 million.

Also under construction for Satmex is the Satmex 7 spacecraft, one of three new-generation, all-electric satellites being built by Boeing Space and Intelligence Systems of El Segundo, Calif. The other two are being built for Asia Broadcast Satellite (ABS) of Hong Kong.

The all-electric design means the satellites will use electric propulsion to make their way to final geostationary position rather than relying on conventional fuel to do the job. The weight savings means these satellites can be launched on smaller, less-expensive rockets.

Satmex 7 is scheduled for launch, together with one of the ABS satellites, aboard a Falcon 9 rocket operated by Space Exploration Technologies Corp. of Hawthorne, Calif., in early 2015.

Northland said the company expects to spend $170 million for the construction, launch and insurance of Satmex 7. As of June 30 it had spent just $11.6 million on the program, Satmex said.

For the six months ending June 30, Satmex reported total revenue of $69.4 million. Its core satellite bandwidth-lease business accounted for $60.4 million of revenue and reported an EBITDA, or earnings before interest, taxes, depreciation and amortization, equivalent to 73 percent of revenue.

The company’s backlog as of June 30 stood at $188.5 million, of which nearly $105 million was from Satmex 5 customers.

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