PARIS — Backers of six proposed European space-science projects, three featuring partnerships with Japan and one with NASA, made their case Dec. 1 under the watchful eye of European Space Agency (ESA) officials who said they cannot afford a repeat of the mismanagement that occurred in the BepiColombo mission to Mercury.

BepiColombo was given final approval in mid-November by the Science Program Committee (SPC), which sets Europe’s space-science agenda within ESA’s budget guidelines. The mission, planned for launch in July 2014, was authorized despite the fact that its cost to ESA, now estimated at 970 million euros ($1.45 billion), is 50 percent above what the SPC thought it was buying when it first approved BepiColombo.

This cost figure does not include several hundred million euros in payload contributions to be financed by individual ESA governments, nor does it include a separate Japanese Mercury orbiter to fly along with ESA’s larger spacecraft.

ESA and SPC members agree that BepiColombo’scost burst through its intended boundaries because of a series of overly optimistic assumptions about its design requirements and its launch mass.

These officials say BepiColombo retains its scientific appeal despite the launch of NASA’s Messenger Mercury orbiter, which has conducted two flybys of the sun’s closest planet since 2004 and is scheduled to enter orbit around Mercury in 2011 for a one-year mission.

But because of its budget history, BepiColombo has become a poster child for how not to perform mission design and cost analysis and has caused ESA and Europe’s science evaluation committees to re-evaluate their procedures.

SPC Chairman LennartNordh said the committee approved BepiColombo by general consensus, concluding that “it is difficult — practically impossible — to cancel a mission that has come so far, when you’ve got contracts with industry in place. The collaboration with the Japanese added to the complexity.”

Nordh said procedures for evaluating future science missions have already been tightened as a result of the BepiColombo experience and would be part of the evaluation of the six candidates for ESA’s so-called M-class missions that made presentations here Dec. 1.

“I am convinced the lesson is well-learned,” Nordh said. “I dare to say this will not happen again.”

ESA officials say they have examined the likely costs associated with all six of the proposed missions, scheduled for launch around 2017-2018, with unprecedented detail and including a review by an independent panel of experts.

Europe’s Space Science Advisory Committee will select three or four of the six proposals in January, with the SPC to give final approval in February. Phase-A design contracts for detailed mission definition will be given to these missions, with two or three to be chosen for full development in late 2011. In July 2012, the selected missions will be analyzed again to verify their costs before full-scale industrial production begins.

“We are all on a marker on this one,” ESA Science Director David Southwood said after the Dec. 1 presentations, referring to the need to respect budget limits. He said ESA’s science directorate assumes its share of the blame for past cost overruns, and so should the science community, which he said “better get to work” on making cost evaluation and control a part of its mandate.

Southwood did not spare Europe’s space-hardware manufacturers from responsibility for past cost problems, saying, European industry has not been covering itself in glory in recent years.”

ESA had set a ceiling of 475 million euros, expressed in 2010 economic conditions, for each of the M-class missions now in competition. The agency evaluated each one for its estimated total cost, and for schedule and other risks associated with hardware development.

The result, which ESA’s Frederic Safa presented at the Dec. 1 meeting: Four of the six missions are estimated to exceed the budget ceiling, two of them substantially so.

Only one of the six, SPICA — the Space Infrared Telescope for Cosmology and Astrophysics — is clearly under the budget ceiling, with costs estimated at 160 million euros. But it is also the only one in which ESA would be a clear junior partner. In SPICA’s case, Japan is the lead investor.

Tadayuki Takahasi, director of external affairs at the Japan Aerospace Exploration Agency, told the meeting that without Europe’s participation, Japan would have to rethink the entire SPICA mission and may need to cancel it.

The Plato mission, to look for Earth-like planets around nearby stars, is estimated by ESA to cost 460 million euros, not counting the payload instruments to be provided by individual European governments.

The Euclid dark-energy mapper, now a Europe-only mission instead of one developed in collaboration with NASA, is just under the ceiling but with numerous questions about whether it will be able to remain there. Euclid costs are estimated at 500 million euros.

The Solar Orbiter mission, which is proposed as a joint mission with NASA, is estimated to cost 490 million euros.

The two other missions, both featuring Japanese collaboration with ESA as mission leader, are estimated to far exceed the ESA cost ceiling. An asteroid sample-return mission dubbed Marco Polo would cost ESA 630 million euros, while Cross-Scale, a seven-satellite constellation designed to study the plasma layer around the Earth, would cost 600 million euros.

Fabio Favata, head of ESA’s science planning office, said the SPC “has complete autonomy” to select however many of the six missions it wishes, while taking account of ESA’s already tight science budget.

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