BOSTON—Astronomy is facing a lean decade. That was the message handed down by senior representatives of the federal agencies that fund much of the field's research in the U.S. during "town halls" with scientists here at the semiannual meeting of the American Astronomical Society.

Science agencies are facing flat or declining budgets, and in that environment new astronomy initiatives will often be possible only at the expense of existing ones. "We can turn off the old to enable the new," NASA Astrophysics Division director Jon Morse said in a May 23 town hall discussion. "That's where we are from a budgetary standpoint." NASA funds space-based projects in the U.S., whereas the National Science Foundation funds terrestrial telescope projects.

Morse said that the number of NASA astrophysics missions in operation had peaked at 15 in 2010 and was now in decline with the phaseout of spacecraft such as the Wide-Field Infrared Survey Explorer and the Wilkinson Microwave Anisotropy Probe. "This portfolio is smaller than it used to be, and it will continue to get smaller," Morse said.

The agency is saddled with disproportionately large costs from building one large mission, the James Webb Space Telescope (JWST), which is in some sense the successor to the Hubble Space Telescope. But JWST's launch date could slip years beyond the current estimate of 2015, pushing other missions further into the future as well. Morse said the mission's timing was currently under review.

In 2010 a committee of the National Research Council (NRC) produced a once-a-decade report intended to advise the funding agencies on which projects to pursue. Among the top-ranked large-scale space missions in that report, the third- and fourth-ranked projects—a gravitational wave detector and an x-ray observatory—have already dropped off the map due to funding constraints. The European Space Agency may revive those missions, but Morse said that NASA did not have the money to participate.

A similar scene is playing out in ground-based astronomy. The NRC decadal survey presumed a doubling of the NSF astronomy budget over the course of the decade, James Ulvestad, NSF division director for astronomical sciences, explained in a May 24 talk. But fiscal realities are playing out somewhat differently; the overall NSF budget has shrunk somewhat and is not likely to increase significantly anytime soon. "We really can't do any of the decadal survey with a flat budget," Ulvestad said.

The NSF is working on the development of the Large Synoptic Survey Telescope, which had been endorsed by the previous decadal survey, in 2001, and was reaffirmed as the top project on the ground in the most recent decadal survey. (The report makes separate recommendations for space-based and ground-based initiatives.) Astronomers have high hopes for that instrument, planned as an 8.4-meter telescope with a 3.2-gigapixel camera on a Chilean mountaintop that can quickly scan the entire sky. But the agency does not have funds available for the second- or third-ranked ground-based initiatives in the 2010 decadal survey—an augmentation of funding for medium-scale projects and a U.S. share in a new giant optical telescope, respectively.

Even a business-as-usual strategy, without pursuing any of the new projects recommended in the decadal survey, would leave the agency with roughly $200 million in annual commitments to manage its ongoing projects, out of a budget of about $250 million. "We would be extraordinarily facility-heavy" if that were the case, Ulvestad said, with very little room to issue research grants.

So the agency is starting a portfolio review to pare back its commitments. "The time for the difficult decisions is here," said Thomas Statler, the NSF extragalactic and planetary astronomy program officer. "This has been said for a long time, but the community will face some tough choices, and we have to do it." He said that the agency was forming a committee to perform a thorough review and to recommend how the NSF can best invest its limited funds to further critical research areas. "These recommendations may include—and this is the bad part—closures, divestments and terminations of programs," Statler said. "We know that this is going to be difficult, and we know that this is going to affect the careers of a lot of people."

One example of the kind of progress that might be possible within a constrained budget is the ongoing upgrade to the Very Large Array (VLA), a chain of radio telescopes in New Mexico funded by NSF. The facility itself is decades old, but recent improvements to the electronics of the array are boosting its performance specs across the board by factors of at least 10, and in some cases by more than 1,000, the National Radio Astronomy Observatory's Rick Perley said at the meeting. The total cost of the upgrade project, known as the Expanded Very Large Array, is around $100 million, far less than it would cost to build a comparable observatory from scratch. The electronic nervous system of the observatory is new, but the radio antennas themselves are the same dishes that were built for the VLA in the 1970s. "They're not particularly fast, but they're paid for," Perley said.

Those relatively cost-effective improvements to existing projects may become more common as funding streams narrow to a trickle. Morse noted that the U.S. is in its third consecutive year with budget deficits of roughly $1.5 trillion, and even a nominal economic recovery in the future would leave an unsustainable chasm between governmental expenditures and revenue. "Something has to happen in the spending part, and that's what Congress is focused on," he said.

"We live in the environment of the U.S. budget deficit," Ulvestad said. "You can't say astronomy doesn't live there."