Once a decade, the U.S. National Research Council convenes a panel of experts to prioritize federally funded ground- and space-based astronomy and astrophysics research for the 10 years ahead. The finished report, called the decadal survey, influences how NASA, the National Science Foundation and the Department of Energy marshal their financial resources to give astronomers and astrophysicists the tools they need to tackle the discipline’s most compelling questions.
More often than not, these well-intentioned decadal survey committees — there are separate ones for Earth and planetary science — load NASA’s cart with more missions than the space agency can possibly hope to accomplish within its limited budget. Scientists adept at calculating interstellar distances and other mind-boggling cosmic sums are notoriously bad at producing accurate cost estimates for spacecraft missions.
Recognizing this, decadal survey committees in years past frequently relied heavily on the optimistic cost estimates put forward by the very industry-government-academic teams posturing to lead missions vying for the survey’s coveted endorsement. In doing so, panels have set unrealistic expectations about what NASA, the National Science Foundation and the Department of Energy can afford to accomplish in a given decade.
Consider the 2001 decadal survey, “Astronomy and Astrophysics in the New Millennium.” It encouraged NASA to tackle during the decade now ending no fewer than nine space telescope missions estimated to cost $5 billion combined, not including international contributions.
NASA so far has managed to build and launch just two of them — the Fermi Gamma-ray Space Telescope in 2008 and the Solar Dynamics Observatory in 2010 — but at costs two to three times higher than estimated in the decadal survey.
Meanwhile, the James Webb Space Telescope — the top priority from 2001 and the only other one of the nine missions to enter development — is struggling to make a 2014 launch without busting its $4.5 billion budget, a figure more than four times what the 2001 survey said the mission would cost.
Recognizing the pinch that Webb and other unfinished business would continue to put on NASA’s $1.1 billion annual astrophysics budget for several more years, the just-released 2010 decadal survey offers an appropriately restrained list of priorities for NASA: three missions for $9 billion, a figure that includes substantial non-U.S. contributions for the two largest observatories, neither of which would launch before 2020.
Top priority was assigned to a $1.6 billion multipurpose mission of the survey committee’s own devising. The proposed Wide-Field Infrared Survey Telescope (WFIRST) would launch in 2020 in place of the Joint Dark Energy Mission that NASA and the Department of Energy have been talking about for years. Equipped with a wide-field, 1.5-meter infrared telescope, WFIRST would seek to settle fundamental questions about the nature of dark energy while doubling as a planet finder.
Remarkably, the 2010 decadal survey assigned second-highest priority to a relatively modest budget augmentation for an existing program — the Explorer line of cost-capped, competitively selected astrophysics missions. Wanting to see more spacecraft like the Wilkinson Microwave Anisotropy Probe, the Wide-field Infrared Survey Explorer and the Swift Gamma-ray Burst Mission — which have done groundbreaking science for a combined price tag that’s a fraction of the cost of a single flagship mission — the 2010 survey asks NASA to devote a steady $100 million a year to the Explorer program over the next decade. This would pay for two Small Explorers, two Medium Explorers and two so-called Missions of Opportunity where NASA-funded instruments fly aboard non-NASA spacecraft.
Finally, a pair of ambitious missions from the 2001 decadal survey — the Laser Interferometer Space Antenna (LISA) and Constellation-X — reappear in the 2010 decadal survey as joint missions with the European Space Agency.
Constellation-X, priced at $800 million in the 2001 survey, would be merged with Europe and Japan’s proposed Xeus mission concept to form the $5 billion International X-ray Observatory.
LISA, meanwhile, is assigned a more realistic price tag — $2.4 billion instead of the $250 million estimated in 2001. And with the European Space Agency-led LISA Pathfinder mission slated for a 2012 launch, technical risks should be substantially reduced by the time work begins on the larger mission.
Time will tell whether the plan laid out in the 2010 decadal survey is any more achievable than the preceding one. But by assuming a flat-to-slightly-declining NASA astrophysics budget and obtaining independent cost and risk assessments, the 2010 decadal has taken a realistic and responsible approach instead of merely drawing up a make-everyone-happy wish list.
NASA also deserves credit for reminding the astronomy community early and often that money will be tight for the foreseeable future.
The universe might be expanding at an accelerated pace, but federal science budgets certainly are not.
