PARIS — The European Space Agency (ESA), on the eve of a decision on near-term science funding that could decrease the program’s buying power in the coming years, has selected the first of what it hopes will be a series of small science missions designed for relatively quick, low-cost development cycles.

The 20-nation ESA’s Science Program Committee (SPC) tentatively agreed to spend 50 million euros ($65 million) in ESA funds, coupled with up to 100 million euros coming from Switzerland and other ESA member states, to launch the Cheops planet-hunting satellite in 2017.

The selection of the Cheops satellite comes just four weeks before ESA governments are scheduled to meet in Naples, Italy, to set ESA’s multiyear program and funding priorities.

Unlike most of what ESA does, the science program is funded by mandatory contributions from the agency’s member governments, with each nation’s share calculated based on the size of its national economy.

The good news for ESA science missions is that their funding is rarely open to question given that it is derived from automatic payments from member governments.

The drawback, however, is that the science program, for which funding is decided every three or four years, needs unanimous consent before its multiyear budget is approved. This situation tends to allow the most financially stressed member governments to determine the multiyear increases even if larger nations would favor higher spending limits.

Each ESA ministerial conference decides the science budget for the next five years, although most ministerial meetings occur every three years. This year’s conference arrives a year later than expected — four years after the previous meeting.

With several ESA nations facing near-crisis situations in their public debt levels, the Nov. 20-21 meeting in Naples could result in a cut in the inflation-adjusted budget of the science program.

“What we are looking at now is likely a flat budget,” said one government official involved in the science budget negotiations. “And when we say flat budgets for ESA, we mean no adjustment for inflation. So we are really talking about a reduction of perhaps 3 percent per year in terms of buying power. But really, in this environment, flat is good.”

ESA science officials for several years have said they would like to add a Small-class mission option to its existing Large- and Medium-class projects.

The S-class missions would have a total budget ceiling of 150 million euros, including spacecraft construction, launch and operations, with ESA’s share limited to 50 million euros. The period from program approval to launch should be no more than four years, and Europe’s new Vega small-satellite launcher should be the preferred launcher choice, if not an absolute requirement.

ESA’s call for proposals in March resulted in 74 responses, of which 26 were considered firm enough to be judged as full mission proposals. The Swiss-led Cheops, a 200-kilogram satellite that will spend 3.5 years in an 800-kilometer orbit tracking the diameter of planets that are discovered when they pass in front of stars, would be ready for launch in 2017, ESA said.

Fabio Favata, head of ESA’s science planning office, said Oct. 22 that the agency will review Cheops’ specific program elements, including the credibility of its cost assumptions, in time to give the mission a final approval in the first half of 2014.

Favata said that while the agency would like to make Cheops the first in a new mission line, it is too early to assume that will be the case, especially with the ESA ministerial conference just weeks away.

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