Minutes after receiving word that the New Horizons spacecraft had survived its historic encounter with Pluto last week, someone in the crowd at the Johns Hopkins Applied Physics Laboratory in Laurel asked mission leaders what's next.
Alan Stern, the principal investigator, answered: to explore other bodies at the edge of the solar system, "and to get funded to do exactly that."
John Grunsfeld, head of NASA's science branch and Stern's boss, responded: "To go where no New Horizons spacecraft has gone before."
But he conspicuously dodged addressing the mission budget.
The uncomfortable exchange underscored the uncertainty scientists face as they look to future missions. Though many believe NASA will approve an extended New Horizons mission to explore bodies beyond Pluto, the fiscal pressures that have chipped away at the space agency's budget mean increased scrutiny for any new projects.
Science advocates hope the intense interest in New Horizons, from social media to the halls of Congress. will help change that by showing proof of strong public support for pioneering missions. And that could mean more projects for the Applied Physics Laboratory, whose scientists designed and managed the Pluto mission on time and within the $700 million budget.
Officially, the science community's priorities for future missions include a Mars rover that could return samples to Earth, a probe to search for the building blocks of life on Jupiter's moon Europa, and a Uranus orbiter. But there are other frontiers that scientists at the Hopkins lab and elsewhere could propose for a visit.
"With this mission, we have visited every single planet in our solar system," NASA Administrator Charles Bolden said Tuesday night to a packed auditorium on the Laurel campus. "Today's mission was just one more step in the journey of getting humans to Mars. It gives us one more piece of the puzzle about our solar system, one more piece to understand how it all formed."
NASA's budget, when adjusted for inflation, has stagnated or declined over the past two decades. It is scheduled to reach about $18 billion in fiscal 2018. But its share of all federal spending has declined steadily, from a peak of 4 percent in the 1960s to less than 1 percent in the 1990s, and about half a percent now.
About $5 billion, roughly a third of NASA's budget, is devoted to scientific missions. The other two-thirds include spending on International Space Station operations and the commercial missions to resupply it, and efforts to build new rockets and vehicles for manned space exploration to replace the discontinued space shuttle program.
The across-the-board federal cuts know as sequestration have had tangible consequences on NASA, said Jim Green, director of the agency's planetary science division, which oversees New Horizons. The division's budget has fallen from $1.5 billion to $1.3 billion.
"The drops in planetary that we've experienced over the last couple years will reflect in fewer missions later on in the decade," Green said. "That's just the way that goes."
There is little disagreement in Washington over the importance of spending on missions such as New Horizons, said Matt Mountain, president of the Association of Universities for Research in Astronomy and former director of Baltimore's Space Telescope Science Institute. At a NASA briefing before the Senate on Thursday, he said, lawmakers and their staffers had endless questions about New Horizons and Pluto.
"There wasn't a single question of 'But what about the budget?'" Mountain said. "It speaks to something in our human psyche, this exploration of the solar system."
Still, budget constraints cause conflict.
Rep. John Culberson, who chairs the House subcommittee that oversees NASA's budget, has called for reviving NASA's Apollo mission "glory days." But the Texas Republican, a member of the fiscally conservative Tea Party Caucus, also said thoughtful prioritization was needed.
"Our budget allocation is going to be tight again this year," he said in a statement in May. "We need to look for efficiencies, streamline programs and make sure the agency stays focused on its core mission."
As scientists readied for the Pluto fly-by last week, Sen. Barbara A. Mikulski said NASA's science budget is underfunded. She said increasing it shouldn't require sacrificing other projects, such as the Space Launch System and the Orion spacecraft proposed for manned missions.
"I want new money," the Maryland Democrat said. "I don't want NASA to be competing against [itself] for projects."
Less money and fewer missions mean more competition for facilities such as the Hopkins lab. It competes against NASA's Jet Propulsion Laboratory at the California Institute of Technology, other university labs, private companies and other NASA centers for pieces of large missions and responsibility for many smaller ones.
The Hopkins lab has launched 66 spacecraft and more than 150 space instruments since the 1970s. Along with New Horizons, recent and ongoing missions include the Messenger probe of Mercury, the Van Allen Probes, which measure harsh radiation surrounding Earth, and Solar Probe Plus, scheduled to explore the sun's outer atmosphere after launching in 2018.
Scientists at the lab are developing two instruments and contributing to several others that will be part of NASA's recently approved (and yet-to-be-named) mission to Europa.
Lab officials expect to hear back in September on proposals made for a class of smaller NASA missions, known as the Discovery Program, said Stamatios "Tom" Krimigis, former head of the lab's space department.
Krimigis said the lab also plans to compete next year for the second mission under NASA's New Frontiers program (New Horizons was the first). NASA officials have not revealed details of that mission.
The Hopkins lab showed it capable of successfully designing, building and managing a mission with New Horizons, Krimigis said.
APL developed the spacecraft ahead of a tight deadline to time its 2006 launch with an opportunity to pass Jupiter and use its gravity to sling the probe to the edge of the solar system, cutting its trip by four years. During the 91/2-year journey, the lab saved about $100 million by flying the spacecraft in a hibernation mode, Krimigis said, reducing staff and operations costs.
And scientists in the mission's operations center, a small room on the Laurel campus lined with monitors, timed its arrival at Pluto within 72 seconds and about 70 kilometers of what they promised.
"Clearly it's a feather on the cap of APL and demonstrates that it is possible for more than one laboratory in the country to do successful planetary missions," Krimigis said.
NASA officials will make a decision on extending New Horizons' mission next year. The mission team has identified two more objects it could explore in the Kuiper Belt, the region of small, icy bodies at the edge of the solar system that includes Pluto. Mission and other planetary scientists expressed confidence that an extension will be approved.
In the meantime, many hope New Horizons will inspire other projects venturing to the outer solar system. But it will take creativity to do so within a reasonable budget and time frame.
Orbiter missions such as the Europa project are more complicated and costly than New Horizons because after speeding to their target, they must slam on the brakes to enter orbit. New Horizons swept by Pluto at more than 30,000 mph.
"We hope that with New Horizons under our belt, we can try to crack open the outer solar system so we can get back there again," said Heidi Hammel, a planetary astronomer and executive vice president of the Associations of Universities for Research in Astronomy.
Green, NASA's planetary science head, said he expects New Horizons will energize the scientific community and spur innovation — something to which the White House and Congress respond well.
"We know it's an austere time and we are so grateful for what we've got," Green said. "But success breeds success."