PRAGUE, Czech Republic — Germany has committed to paying a 38 percent share of an estimated 3.8 billion euros ($5.2 billion) that European governments will need to continue their work on the international space station (ISS) in the next 10 years, the head of Germany’s space agency said Sept. 29.

Johann-Dietrich Woerner, chairman of the board of the German Aerospace Center, DLR, said Germany is now waiting for Europe’s other space station participants, led by France and Italy, to state their commitments to the station’s five-year extension, to 2020.

“We have a firm commitment from Germany to support space station utilization through 2020 at the same 38 percent level we have been in the past,” Woerner said in an interview at the 61st International Astronautical Congress here. “We are waiting for the other [European] countries to do the same. These countries have to accept that we want nominal ISS operations for the period in question.”

The 18-nation European Space Agency (ESA) remains the only space station partner not to have signaled its agreement to the proposed five-year station life extension. ESA Director-General Jean-Jacques Dordain said Sept. 27 at the 61st International Astronautical Congress that he did not want ESA nations to approve the station’s extension without firm budget commitments.

None of ESA’s participating nations has objected to extending the station’s life, Dordain said.

“What still needs to be decided is the cost, and the scale of contributions,” he said. “I don’t want an approval now without deciding this aspect as well. I hate decisions that are ‘subject to availability of funds.’ What we need to agree to now is the distribution of costs. That is the difficult part.”

 ESA nations in 2008 agreed to fund the operating costs of the station at a rate equivalent to about 290 million euros per year, in today’s economic conditions, through 2015. The agreement came only after long debate over how much the station would cost.

Simonetta di Pippo, ESA’s space station director, said Sept. 30 that this agreed-to rate underfunds the station by up to 30 percent, meaning ESA will be forced to cut back on experiment conducted at the orbital complex, or find other cost savings, if the funding level is not increased.

Speaking with reporters, di Pippo said ESA has a range of 10-year station operations cost estimates tied to various levels of station use. Confirming that DLR has informed ESA of its commitment through 2020, she said the German estimate of 3.8 billion euros assumes no development of an upgraded version of ESA’s Automated Transfer Vehicle (ATV) to permit it to return station cargo to Earth.

Woerner said Germany is “ready to discuss” development of an upgraded vehicle. France and Italy, which currently pay about 27 percent and 19 percent of Europe’s space station costs, respectively, have not come out in favor of the ATV upgrade.

Woerner said some European nations appear to believe station operations could be done for less than the 3.8 billion euros DLR has proposed, without compromising the utilization program. “We would be happy to see those numbers,” he said.

ESA has begun a review of its station operations in an attempt to find cost savings that could be used to offset new charges for operations or for major new hardware such as the Advanced Return Vehicle.

Di Pippo said the agency has begun talks with the Japan Aerospace Exploration Agency to determine whether Japan’s plans to upgrade its current throwaway H-2 Transfer Vehicle cargo tug could be merged with ESA’s vehicle into a single program to develop a vehicle with payload-return capabilities. Di Pippo said a proposal to spend 150 million euros on preliminary work for an Advanced Return Vehicle will be submitted to ESA governments this year once the station-extension budget has been set.

Full Advanced Return Vehicle development costs, including the first mission and its launch, have been estimated at around 1.4 billion euros. If the preliminary work is approved this year and full development voted at a meeting of ESA governments now planned for mid-2012, a first flight could occur in 2018. Di Pippo is positioning the vehicle as an asset that would serve Europe’s future space-exploration plans beyond the space station.

Partly offsetting the Advanced Return Vehicle development costs would be an ESA decision to cancel plans for a sixth and seventh ATV vehicle, which otherwise would have to be ordered to fulfill ESA’s station obligations to 2020.

In another proposal that could affect station life-extension costs, ESA is weighing a program to develop an advanced closed-loop system to recycle water, reducing the need for water to be delivered by freighter. This could permit the agency to offset some of its annual station operating cost obligations to NASA, the station’s general contractor.

Di Pippo said that with the other station partners — the United States, Russia, Japan and Canada — all having signaled their endorsement of the extension to 2020, Europe’s continued debate over the issue risked becoming an embarrassment.

But she said there was little doubt that ESA governments would agree to the extension by the end of this year. She said ESA also has begun work on certifying its space station hardware to 2028. “We are already beginning to insert the station into our longer-term plans for exploration,” di Pippo said. “I am confident that 2020 is not the end of the story.”

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