TORONTO — The prime contractor for Europe’s two-launch ExoMars mission on Oct. 1 said it is on schedule for both mission segments — one to launch in 2016, the other in 2018 — but that it needs a commitment from European governments in December to complete the agreed-to funding package.

Thales Alenia Space said that while it has sufficient funds to continue working on both missions into 2015, the 2018 launch, featuring a European Mars rover vehicle, will run out of cash sometime next spring without a fresh funding commitment.

The missing funds, totaling about 185 million euros ($240 million), have long been a sore point among European Space Agency governments, several of which have chafed as ExoMars grew from a technology demonstration mission to a full-scale science and exploration program with an estimated cost of 1.2 billion euros.

With occasionally creative backing from ESA Director General Jean-Jacques Dordain, who has succeeded in finding ExoMars backing in places few would have thought to look, the mission is now moving forward with the Russian space agency, Roscosmos. Roscosmos is providing two heavy-lift Proton rocket launches for ExoMars, and is also furnishing hardware and its own experiment package for the missions.

The Italian Space Agency, ASI, is leading ESA’s ExoMars funding effort but its available cash is already stretched thin by expected commitments for the international space station, the Italian-led Vega rocket and other obligations.

ESA ministers are scheduled to meet Dec. 2 in Luxembourg and ExoMars, while not formally on the agenda, will nonetheless be a topic as any delay in funding will make it difficult to meet what Thales Alenia Space officials said is an already tight calendar.

“We have not yet gone to double shifts in our factory, but that is something we may need to do,” said Vincenzo Giorgio, the company’s vice president for science and exploration. “For the 2018 mission, we don’t need a huge amount of money immediately, but we need a commitment from ESA members that this money will be available to the program. The funding we have for the 2018 portion will last until sometime in the second quarter of 2015.”

With Italy already paying the largest share of ExoMars, the most likely sources for the additional funding are Britain and Germany, whose companies — Airbus Defence and Space in Britain, OHB AG in Germany — have been given major roles.

ExoMars program managers can only hope that the often complicated horse trading that characterizes ESA ministerial conferences ends up with the needed funds. ExoMars is Europe’s flagship exploration project for now.

In a presentation here during the 65th International Astronautical Congress, Annamaria Piras, an ExoMars program manager at Thales Alenia Space, said the earlier of the two missions, set for launch in January 2016, “is going smoothly. We are on schedule.”

Piras said the 2016 mission’s two main elements, the Trace Gas Orbiter and the entry, descent and landing module, will begin integrated tests at Thales’ Cannes, France, facility starting in early 2015, with delivery to Russia about two months before the January launch.

ESA governments have hesitated in fully funding the ExoMars program in part because several governments did not believe Thales Alenia Space could recover from NASA’s decision to disengage from the program in time to make the 2016 and 2018 launch windows.

For the 2018 launch, NASA’s decision to sharply scale back its ExoMars role meant that work on a U.S.-European rover was shelved in favor of an all-European vehicle.

Giorgio said the rover work is on track.

One element of ExoMars that was not dealt with at the conference here was the status of Russia’s ExoMars work. ESA and Roscosmos are now tethered to each other on the mission; neither can succeed without the other.

Giorgio specifically praised the priority Roscosmos has placed on ExoMars and said NPO Lavochkin of Moscow, the principal Russian ExoMars contractor, appears to have assigned the needed resources to the mission.

Russia is providing the descent module for ESA’s rover, among other elements. The launch has a 21-day launch window starting May 7, 2018.

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