PARIS — NASA and the European Space Agency (ESA) announced Jan. 16 the signature of an implementing agreement under which ESA will supply the service module for NASA’s second Orion Multi-Purpose Crew Vehicle mission, now scheduled for 2017.

The agreement “puts ESA on the critical path, and we don’t do that lightly,” William Gerstenmaier, NASA associate administrator for human exploration and operations, said during a press briefing at NASA’s Johnson Space Center in Houston.

The agreement calls for ESA to adapt hardware originally built for Europe’s Automated Transfer Vehicle (ATV) cargo tug used to deliver supplies to the international space station. The Orion service module will include propulsion and crew supplies and will be attached under the capsule’s crew compartment.

ESA and NASA officials at the briefing agreed that the schedule for development of the service module is tight. Bernardo Patti, ESA’s manager for space station operations, said during the briefing that a preliminary design review would be completed in the second half of 2013.

The 20-nation agency has not yet hired a service module prime contractor but Astrium Space Transportation, which builds the ATV, is the most likely candidate.

ESA governments in November agreed in principle to join NASA in the Orion project, but only approved 250 million euros ($330 million) of the 455 million euros needed to perform the work needed under the agreement with NASA. The agency has planned a meeting of its ministers for mid-2014 and it is only at this time that the remaining funds will be made available.

ESA governments participating in the space station all agree that the orbital complex should remain in operation at least through 2020, but they have only approved funding through 2014. Several ESA nations, including France — ESA’s second-largest contributor to the station, behind Germany — want an agreement on station operations cost sharing before committing to 2020.

Thomas Reiter, ESA’s director of human spaceflight and operations, said the unfunded part of the Orion service module is little more than a formality, and that ESA governments have agreed to join NASA in Orion and will vote the remaining monies in 2014.

To build Orion’s service module, ESA is using funds that would be due NASA in any event if, as the agency has said is all but certain, ESA votes to continue its use of the station to 2020.

ESA’s 8 percent share of the station’s resources means it owes NASA, as the station’s general contractor, about 150 million euros per year to offset European use of the facility.

Up to now, ESA has been providing NASA with ATVs to carry fuel, food, water and other supplies to the station, and to reboost the entire complex, whose orbit degrades with atmospheric drag and must be raised.

ESA decided that it will produce no more ATV vehicles after the fifth, scheduled for launch in 2014. The question then became what it could barter with NASA that both agencies would accept.

ESA has closely tied its Orion work to the amount of funds it owes NASA for station operations between 2017 and 2020 — thus the 455 million euro commitment for Orion.

NASA is providing the service module’s main engine and Orion prime contractor Lockheed Martin Space Systems of Denver will be doing the integration work.

What happens after the 2017 flight is unknown. Gerstenmaier said NASA has protected itself against any eventuality by retaining intellectual property rights for the service module work, and is ready to step in — presumably to assign the service module’s construction to Lockheed Martin — in the event the trans-Atlantic agreement is not extended.

Mark Geyer, NASA’s Orion project manager, said during the briefing that the ESA agreement includes a limited number of spare parts that will be used either to replace hardware that is broken during preparation of the 2017 mission or to start construction of Orion’s next mission in 2021.

“We’ve made no decisions” on what happens for future Orion service modules, Gerstenmaier said. But he said NASA would like to use the agreement with ESA as a showcase of what international cooperation in long-term space exploration might look like.

Peter B. de Selding was the Paris Bureau Chief for SpaceNews.