LUCERNE, Switzerland — The 22-nation European Space Agency on Dec. 2 forced its science program to lay an offering at the alter of the agency’s struggling ExoMars mission with Russia, allowing a European rover to be launched in 2020 to complement the Mars orbiter already in service.

Appearing at a briefing after a two-day meeting of the agency’s member governments, ESA Director-General Jann Woerner did his utmost to cast the effect on the agency’s five-year science budget in the best possible light, but in the end accepted that planned future science missions might need to be delayed.

The budget adopted by the ministers calls for spending 508 million euros ($552 million) per year on science missions between 2017 and 2022. Starting in 2018, that figure will rise by 1 percent per year, with no accounting for inflation.

Woerner said he tried to get the agency’s member states to incorporate an inflation metric into the accounts, and to add a 1 percent per year increase on top of that.

It didn’t work.The result, as European government officials agreed after the conference, will be a decrease in science purchasing power in the coming years. One or more Medium-class missions still not selected will need to be delayed. Any hope that the Lisa gravity-wave observatory could be completed earlier than 2034 — a launch date of 2029 had been cited as feasible, budget permitting — has now almost certainly been lost.

But the news gets worse for science. ESA came into the Lucerne meeting needing some 440 million euros to complete the ExoMars 2020 mission, including operations of the orbiter and rover.

Some ExoMars work to move from Russia to Europe

Already the agency had been obliged to accept doing more work than predicted on ExoMars to lighten the load on the Russian contractors and reduce the chance of further delays or cost increases. As a result, certain integration and testing work that had been slated for Russia will now be done in France and Italy.

Sensing that soliciting 440 million in the already over-budget ExoMars would be difficult, Woerner — borrowing a page from his predecessor, Jean-Jacques Dordain, a fervent ExoMars backer — asked his governments for some 340 million euros.

The remaining 100 million euros, he said, would be found elsewhere, by ESA, from the agency’s budget for mandatory activities.

Almost all of what ESA does is funded by optional contribution of each government. But science and ESA”s internal operations are paid by automatic contributions from each member nation based on its gross domestic product.

That gives the science program a level of predictability that no other program has. But it also makes it extremely challenging to increase the budget. Every ESA nation has to agree, since all of them will be asked to raise their budgets by the same percentage amount.

In addition to the barely-treading-water 1 percent increase, the science program will now have to absorb part of the cost of the 100 million euros being directed to ExoMars.

The science and ExoMars budgets were part of a package totaling 10.3 billion euros that ESA governments approved over periods of between three and eight years. The agency had asked for 11 billion euros, but Woerner said the results were more than satisfactory.

International Space Station commitment to 2024

Once ExoMars was put on solid financial footing, the ESA nations participating in the International Space Station needed to find consensus on whether to follow the United States, Russia, Japan and Canada and agree to continue space station operations to 2024.

David Parker, director of human spaceflight and robotic exploration, said ESA nations agreed to spend 807 million euros on space station exploitation, plus another 153 million euros for experiments aboard Europe’s Columbus laboratory module, attached to the station.

Europe has already agreed to build a service module for NASA’s Orion crew transport vehicle to offset ESA’s 8.3 percent annual pro rata share of the station’s common operating costs.

Parker said the Lucerne decision means Europe will now provide a second service module, including its full construction. Other barter elements with NASA will be sought to offset Europe’s share of operating costs through 2024.

Asteroid Impact Mission with NASA set side, for now

ESA had asked its governments for a modest program to start work on an Asteroid Impact Mission (AIM) with NASA as part of a growing sense in Europe that it needed to be involved in future planetary defense activities.

But AIM never found the necessary support to get off the ground. Woerner nonetheless said several ESA member governments wanted study work to continue so that an AIM-like project could be undertaken at some point in the future.

Space Rider: Orbital and reusable

The Italian government’s determination on ExoMars overshadowed the fact that Italy’s strong backing of the Space Rider mission allowed that program move to the critical design review, with a launch possible in 2021, according to Daniel Neuenschwander, ESA’s director of launchers.

Space Rider will use the structure from the Italian-led Intermediate Experimental Vehicle, which orbited the Earth and then landed in the sea, to build a vehicle that would be launched aboard an Italian-led Vega rocket into low Earth orbit to perform microgravity experiments and then return to Earth to land, on wheels, at an airstrip. It is designed to be refurbished and reused.

French-led Prometheus reusable rocket engine

With France as the prime mover, ESA also agreed to spend up to 100 million euros on a liquid oxygen/methane engine, called Prometheus, that ultimately could form the basis of a reusable first-stage for a future rocket.

The future Ariane 6 heavy-lift vehicle, and the future Vega-C-Plus rocket, both now in development and scheduled for first launches in 2020 and 2019, respectively, have design to cost as their goal but are expendable rockets.

Joel Barre, deputy director of the French space agency, CNES, said after the ministerial conference that France is paying the vast majority of the Prometheus program so as not to lose development time.

With the Ariane 6 rocket now fully funded, ESA governments can turn their attention to next-generation launcher technologies, including possible reusable segments.

Unlike launch-service provider SpaceX in the United States, France and ESA are not fully convinced that reusability is the key to future cost competitiveness, especially if the launcher in question cannot count on dozens of missions per year.

But Barre said France is determined to test reusability technologies.