PARIS — Science chiefs from the European Space Agency (ESA), NASA and the Russian space agency Roscosmos have begun laying the ground work to redesign a two-pronged robotic Mars mission to accommodate greater participation by Russia.

The ExoMars mission was upended earlier this year by uncertainty surrounding NASA’s ability to fund the joint campaign.

On Dec. 7 in Paris, ESA Director of Science and Exploration Alvaro Gimenez-Canete met with his agency counterparts — NASA Acting Associate Administrator for Science Charles Gay and Roscosmos Deputy Head Anatoli Shilov — to establish a pair of trilateral working groups charged with redesigning ExoMars with full Russian participation in mind, in exchange for launching the 2016 leg of the campaign on a Russian Proton rocket, ESA spokesman Franco Bonacina says.

The two working groups — one charged with examining payload options, the other with considering the technical feasibility of a Proton launch — have until early February to report back to their respective science chiefs, Bonacina says.

NASA had previously offered to pay for an Atlas 5 launch that would send ESA’s entry, descent and landing demonstrator and data relay satellite — equipped with a methane-sniffing sensor and other science instruments — to Mars in 2016.

Under the original plan, that mission was to be followed two years later by a NASA-led campaign that would deliver a NASA rover and an ESA rover to drill and collect soil samples on the Martian surface.

In April the U.S. space agency said budget cutbacks were threatening funding for ExoMars. After months of back and forth between the two agencies, during which NASA pulled the plug on its 2018 rover, NASA said in September it could not commit to launching the 2016 leg of the mission. As a result, ESA has turned to Roscosmos for possible launch of its planned Mars orbiter in the 2016 window.

During the meeting, Russia agreed at least in principle to provide a Proton rocket for the 2016 launch, pending resolution of several outstanding issues, including space for Russian instruments or other technologies aboard the mission as well as rights to data collected by a proposed ESA-NASA ExoMars rover that could launch in 2018, Bonacina says.

Although the heads of the three agencies are not expected to meet before February, ESA Director General Jean-Jacques Dordain is slated to speak with Roscosmos chief Vladimir Popovkin Dec. 19-20 in Moscow before moving on to the Dec. 21 Soyuz mission that will launch ESA astronaut Andre Kuipers to the International Space Station from the Baikonur Cosmodrome in Kazakhstan.