WASHINGTON — Faced with a shrinking budget, NASA’s Planetary Science Division is instituting a strict new approval process for extended missions, and not even marquee probes such as the Cassini Saturn orbiter will be exempt from scrutiny, a senior agency official said.

The multibillion-dollar Cassini orbiter, part of an international collaboration between NASA and the European and Italian space agencies, completed its primary mission in June 2008 but continues to return scientific data under an extended mission that is expected to cost $60 million in 2012 alone.

James Green, director of NASA’s Planetary Science Division, said the future of Cassini and at least eight other ongoing missions including Mars rovers and a Venus orbiter will be placed under the microscope by senior planetary scientists in March. The panel is to hand in its recommendations shortly thereafter, he said.

“We’re going to … obtain input from the review panel and make some strategic decisions on what can and cannot be funded,” Green said Oct. 27. “It may be — and I don’t know this for a fact — that we will have to not fund some missions.”

The review panel will meet once every two years to determine whether the “science per dollar” yielded by extending a planetary mission is sufficient to justify continued funding.

Green detailed his division’s planned austerity measures during a meeting of the NASA Advisory Council Planetary Science subcommittee. Members of the planetary science community participated via phone and Internet.

Green continued to tread softly around questions about new program starts during the meeting. “That’s all part of the embargoed [2013] budget that we’re working on with [the White House Office of Management and Budget] right now,” Green said.

He did note that the Osiris-Rex asteroid sample return mission is still slated for a 2016 launch.

NASA in May announced that Osiris-Rex would be the 12th mission in its Discovery program of scientist-led missions. Excluding the price of a launch, Osiris-Rex is projected to cost about $800 million, Green said.

Green also said that on Oct. 31, the planetary science subcommittee will provide an update to the full NASA Advisory Council about NASA’s contribution — or lack thereof — to a joint Mars exploration program with Europe.

NASA’s inability to make a financial commitment to either a 2016 Mars orbiter or a 2018 rover has placed the program’s future in question. The European Space Agency recently invited the Russian Federal Space Agency, Roscosmos, to join the so-called ExoMars mission as a full partner. Roscosmos, which is being asked to launch the 2016 orbiter aboard a Proton rocket, has not yet made a firm commitment.

Meanwhile, Green also sought to reassure the subcommittee that despite NASA’s budget woes, the agency has no plans to abandon planetary science activity.

“It is not true the planetary program is being killed,” Green told subcommittee members. He was referring to an assertion by Mars exploration advocate Robert Zubrin in an opinion piece published Oct. 26 by The Washington Times.

“Word has leaked out that in its new budget, the Obama administration intends to terminate NASA’s planetary exploration program,” Zubrin wrote. “The Mars Science Lab Curiosity, being readied on the pad, will be launched, as will the nearly completed small MAVEN orbiter scheduled for 2013, but that will be it. No further missions to anywhere are planned.”

Zubrin is the president of the Mars Society, a group based in Lakewood, Colo., that advocates for manned and robotic missions to Mars.

NASA’s Planetary Science Division does indeed face a declining budget. U.S. President Barack Obama, in his 2012 NASA budget request, asked for $1.54 billion for planetary science, but funding for that account is projected to drop steadily in subsequent years, to about $1.27 billion by 2016.

In their 2012 spending bills for NASA, the House and Senate Appropriations committees allocated $1.5 billion to planetary science. To date, neither chamber has brought a bill that includes NASA’s budget up for a floor vote.

The U.S. government is currently funded by a temporary spending measure that preserves 2011 funding until Nov. 18. The federal government’s fiscal calendar turns over Sept. 30.

Dan Leone is a SpaceNews staff writer, covering NASA, NOAA and a growing number of entrepreneurial space companies. He earned a bachelor’s degree in public communications from the American University in Washington.