Key decisions on Europe’s capability and activity in space will be taken by research ministers on Tuesday.
They will come together in Luxembourg to resolve the future of the Ariane rocket and the continent’s involvement in the International Space Station.
The European Space Agency’s (Esa) Council Meeting at Ministerial Level also has the Red Planet on its agenda.
Money must be found to fill a budget hole in the flagship ExoMars mission due to leave Earth in 2018.
But it is an agreement on a next-generation Ariane launcher that will be pivotal to the outcome of the gathering.
Ministers look set to approve the full development of a new rocket to replace the continent’s existing workhorse.
The Ariane 5 has come to dominate the market for putting up big commercial satellites, but it is now under pressure from competitor services offering lower prices.
A new Ariane 6 concept has been proposed, and ministers must sanction the way ahead and fund it.
They are being asked to commit 3.8 billion euros (£3bn; $4.7bn), which will cover not only the A6’s development but also an upgrade to Esa’s small Italian-built Vega rocket.
It has taken months of negotiation to get to this point, involving government and industry.
France, which has been most keen to move to a next-generation launcher, will be putting up most of the money on Tuesday.
But it needs Germany’s support financially and programmatically.
The Germans had wanted a two-step project involving an upgrade to the existing Ariane 5, but they are now ready to forego this demand – provided their interests are also satisfied on the space station.
Johann-Dietrich Woerner, who heads the country’s national space agency (DLR), told the BBC: “We will participate in A6 with a big amount of money, up to 20% if necessary for the overall programme, but it depends also that France and Italy are going ahead with ISS.
“They said that if Germany participates in A6, if it agrees in A6 – then they will participate in the ISS. Now that Germany agrees, I expect France and Italy to confirm their proposal.”