Sunrise as viewed from the International Space Station in November. Framing the edge of sun is the Soyuz TMA-17M (front) which brought NASA astronaut Kjell Lindgren, JAXA astronaut Kimiya Yui and Russian cosmonaut Oleg Kononenko to the station and a Russian Progress 60 (back) cargo craft which arrived back in July. Credit: NASA JSC

PARIS — Europe’s two biggest backers of the International Space Station are suggesting it’s possible Europe may end its space station role in 2020 despite the fact that its major partners – the United States, Russia, Japan and Canada – have all said they will continue using the orbital complex until at least 2024.

In separate statements Jan. 4 and Jan. 5, the heads of the French and German space agencies said a detailed study is under way to assess the future operating cost of the station, and whether the cost can be justified given the pressure on near-term budgets.

Pascale Ehrenfreund, chairman of the board of the German Aerospace Center, DLR, which is Germany’s space agency, said DLR would make no promises until after a full review of ISS’s value.

“In view of the high cost involved and the resulting implications on budgets of [European Space Agency] member states, we have to evaluate very carefully costs and benefits of a continued participation in the ISS,” Ehrenfreund said in a Jan. 5 statement in response to SpaceNews inquiries.  “It’s only based on this evaluation that we will be able to take a definite position.”

Germany has been Europe’s ISS champion — its biggest paymaster and most vocal booster — for more than 20 years and at times has had to strong-arm France into boosting its support under threat of reduced German backing of Europe’s Ariane rocket program, a French priority.

In December 2014 France agreed to return its space station support to its mid-1990s commitment levels as part of a broad agreement that included a large German role in the future Ariane 6 rocket.

Jean-Yves Le Gall, president of the French space agency, CNES, said Jan. 4 that France would not announce a position for or against post-2020 ISS support until it had worked out a common position with Germany.

Le Gall invoked the pressure on German public spending caused by the massive influx of refugees onto German territory in 2015, and said no common position would be clear until the eve of the next meeting of European Space Agency ministers, set for December in Lucerne, Switzerland.

ESA governments, led by France and Germany, regularly play a kind of liar’s poker with each other, feigning budgetary strength or weakness to win overall ESA support for a given program, or to encourage other nations to increase their contributions with the implied threat of program cancellation.

Whether that is what is happening now is difficult to discern. At the last ESA ministerial meeting, in December 2014 in Luxembourg, Germany and other governments committed to a 10-year program of support for current and future launch vehicles valued at more than 8 billion euros ($8.8 billion).

The commitment makes it more difficult to engage in the space-station-versus-launch-vehicles negotiations.

Le Gall said further pressure on Europe’s space station involvement beyond 2020 is the possibly short duration of a barter arrangement with NASA. Up to now, Europe has provided space station cargo supplies to offset its 8.3 percent share of the station’s common operating costs, which without the barter would be due to NASA in cash.

ESA retired its Automated Transfer Vehicle cargo vehicle after five flights. NASA and ESA, after lengthy negotiations, agreed to extend the barter to include Europe’s service module contribution to NASA’s Orion crew exploration vehicle – whose mission is not centered on the international space station but destinations beyond low Earth orbit.

Europe is now providing one service module copy, and a set of spare parts for a second flight.

ESA has already reduced its ISS operating costs – not including the common operating charges – by more than 30 percent in recent years, in part by outsourcing much of the work to Airbus Defence and Space and in part by consolidating ground operations.

If France and Germany are contemplating a dip in station commitment, Britain is moving in the other direction on the strength of the appeal of ESA astronaut Tim Peake, a British national who is now part of the space station crew. But Britain remains a minor contributor to ESA’s overall space station budget.

France may regain its space station enthusiasm in November with the launch of Thomas Pesquet, a French national in the ESA astronaut scheduled for launch to the station then. French President Francois Hollande in December celebrated Pesquet’s mission at a public ceremony.

ESA budgeted human spaceflight, which is mainly the space station, at 371 million euros in 2015, or 8.4 percent of its total budget.

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