WASHINGTON — NASA and the European Space Agency (ESA) will have to revisit plans for joint flagship-class planetary missions now that it has become clear that the U.S. space agency’s budget will not support any such projects for the foreseeable future, according to a senior NASA official.

“In terms of our flagship missions, the ones that we’ve planned with ESA, it is clear we must go back to the negotiating table and work new agreements if we expect to maintain our partnership with our best foreign partners to date,” said Jim Green, director of NASA’s Planetary Science Division. NASA and ESA have been planning joint missions to collect martian soil samples for possible return to Earth and to send a pair of probes to orbit Jupiter’s ice-covered moon Europa.

Green’s remarks were made March 7 in Houston during the rollout of a new report that lays out the science community’s top priorities in planetary exploration for the next 10 years. The long-awaited National Research Council survey, “Vision and Voyages for Planetary Science in the Decade 2013-2022,” comes as NASA is facing a declining budget profile for deep-space probes.

The survey was based on last year’s budget projections that assumed steady growth in NASA’s planetary science budget from 2011-2015. The latest projections, released Feb. 14 with U.S. President Barack Obama’s 2012 spending request, show that budget increasing slightly next year, to $1.54 billion, but then declining on an annual basis to $1.25 billion by 2016.

Even under the rosier budgetary scenario, the decadal survey committee concluded that a big planetary mission is not in the cards unless NASA can scale back current designs to lower projected costs. However, the panel did recommend several missions in the more modest New Horizons and Discovery classes, which have budgets in the neighborhood of $1 billion and $425 million, respectively.

Steve Squyres, a Cornell University professor and chairman of the National Research Council decadal survey panel, said the current budget request, if implemented, “would mean the end of flagship-class science at NASA in the planetary program,” a revelation that did not sit well with planetary exploration advocates.

“NASA is charged with exploring and innovating, but the Congress and Administration routinely turn the spigot on and off, and then seem outraged when NASA fails to meet their schedules and expectations,” Bill Nye, executive director of the Pasadena, Calif.-based Planetary Society, said in a March 7 statement.

In its survey, the National Research Council used independent cost estimates by the Los Angeles-based Aerospace Corp. to conclude that the community’s top flagship-class mission priority, the Mars Astrobiology Explorer-Cacher, would cost $3.5 billion as currently designed, followed by the Jupiter Europa Orbiter at $4.7 billion. The study also found that even if the missions were scaled back, NASA would be hard-pressed to carry them out under likely budget scenarios.

Even before the release of the survey, scientists were fretting about the implications of NASA’s planetary science budget.

Ronald Greeley, an Arizona State University professor who chairs the NASA Advisory Council’s planetary science subcommittee, said March 2 he was gravely concerned that the budget leaves no room for new flagship missions “without wrecking the rest of the planetary program.”

Speaking in Houston, Squyres and Green offered some hope that the budgetary outlook could change. “From [2013] on out it’s a notional budget,” Green said. “What that means is … the current lines we’re all familiar with — Discovery, New Frontiers, Mars, etc. … we have the opportunity to change the content of the program within the president’s budget.”

But Greeley said he is worried the requisite tradeoffs could jeopardize missions already in the pipeline.

“NASA has the potential for reallocating funds, and within the Planetary Science Division that would be a possibility, but it would preclude other things ongoing in the division, including the missions that are in development or potentially on their way now,” Greeley said. “Even with a stripped-down Mars or Europa mission, it still would take a substantial flagship-class new start.”

Adding to Greeley’s concern is the fact that developing and flying a flagship mission to the outer solar system takes years.

“Without a new start within the next couple of years, we really are not looking at new data from the outer solar system for more than a decade,” Greeley said. “Europa is a 2028 operation, and that would be with a new start almost immediately.”

Green said implementing the decadal survey’s priorities would take time to win White House and congressional approval, and that “because we are in economically difficult times, we should not plan or expect new starts to occur.”

He noted that while the president’s proposed budget has not been finalized, “the planetary budget can go down … and it will go down I can assure you if we can’t get behind the budget and behind the decadal and that is critical to understand.”

Squyres urged members of the science community to appeal to U.S. lawmakers for support.

“We have an opportunity to use this as a rallying point and to speak together as a community with one voice in support of planetary exploration,” he said. “If we do not speak up then there is some chance that we’ll see a program like the one represented by this budget and all that it implies.”

Greeley said it would be a shame if NASA were to lose its standing as a leader in planetary exploration.

“We as a nation need to think about the pre-eminence of NASA as the explorer of the solar system, and without flagship-class missions that’s a title that’s going to slip,” he said.