What happens to a dark energy dream deferred? An ambitious $1.6 billion spacecraft that would investigate the mysterious force, and search out planets around other stars, might have to be postponed for a decade, NASA says, because of cost overruns and mismanagement on a separate project, the James Webb Space Telescope.
The news has dismayed many US astronomers, who worry they will wind up playing second fiddle to their European counterparts. “How many things can we do in our lifetime that will excite a generation of scientists?” asked Saul Perlmutter, an astronomer at the University of California, Berkeley, who is one of dark energy’s discoverers.
Last summer, after 10 years of debate and interagency wrangling, a committee from the National Academy of Sciences gave highest priority among big space projects in the coming decade to a satellite telescope that would take precise measure of dark energy, as it is known, and also look for planets beyond our solar system. The project goes by the acronym WFIRST, for Wide-Field Infrared Survey Telescope. The Academy’s report was ambushed by NASA’s announcement in November that the successor to the Hubble, the James Webb Space Telescope, scheduled for a 2014 launching, would require at least another $1.6 billion and several more years to finish, pushing the next big mission to 2022 at the very earliest.
Buying a share in Euclid...
The Webb will search out the first stars and galaxies to have formed in the universe, but is not designed for dark energy. To take up the slack until 2025, or whenever the mission can finally fly, the space agency has proposed buying a 20 per cent share in a European dark-energy mission known as Euclid that could fly as soon as 2018. In return, NASA would ask for a similar investment by Europe in WFIRST.
Euclid must survive a bake-off with two other projects before it is approved by the European Space Agency. Not until then, European astronomers say, will they be able to talk about changes to the project. NASA has not said how it plans to get the $1.6 billion it needs to finish the Webb telescope, and thus how much will be left for other projects this decade. Some of the answers will be in the 2012 NASA budget due next month.
Jon Morse, director of astrophysics at NASA headquarters, said NASA was committed to carrying out the recommendations of the original Academy survey that endorsed WFIRST.
The discovery a decade ago that the universe is speeding up has thrown into doubt notions about the fate of the universe and of life within it, not to mention gravity and even the nature of the laws of physics. It is as if, when you dropped your car keys, they shot up to the ceiling. Physicists have one ready-made explanation for this behaviour, but it is a cure that many of them think is worse than the disease: a fudge factor invented by Albert Einstein in 1917 called the cosmological constant. He suggested, and quantum theory has confirmed, that empty space could exert a repulsive force, blowing things apart. But the best calculations predict an effect 10 to the exponent of 120 times greater than what astronomers have measured, causing physicists to metaphorically tear their hair out and mutter about multiple universes.
Missions that went nowhere
Perlmutter, who works in the Department of Energy’s Lawrence Berkeley National Laboratory, proposed a dark energy mission known as SNAP (Supernova Acceleration Probe) in 1999. In 2003, the White House asked the Energy Department to partner with NASA on the project, which became known as JDEM, for Joint Dark Energy Mission, and a call went out for competing proposals. But NASA and the Energy Department found it hard to collaborate, and several rounds of meetings and committees went nowhere. In 2008, NASA and the Energy Department budgeted $600 million, not including launching costs, for a mission, but a working group of dark-energy scientists could not come up with a design to match.
Morse submitted a couple of versions of the dark energy mission to the National Academy of Sciences panel, known as Astro2010, that was charged with setting priorities for the astronomical community for the next decade. Alan Dressler of the Carnegie Observatories, who led one of the panel’s subcommittees, noticed that three of the submitted projects, including dark energy, a search for planets around other stars, dubbed exoplanets, and a survey of infrared radiation from the heavens, all required the same hardware. He proposed combining them into a larger mission (WFIRST), in a project that could launch around 2020.
The European Space Agency had also made dark energy a priority. Last February, the Europeans sent NASA a letter offering the Americans a 20 per cent piece of Euclid and two slots on the mission’s science team. U S astronomers were ambivalent. Joining Euclid would divert resources from their own mission, thus delaying it. In September NASA’s advisory committee on astrophysics, led by Boss of the Carnegie Institution, concluded Euclid could spend three or four years “skimming the cream off the dark energy pail” before WFIRST got into the sky. Both Boss’s council and yet another committee, the Astronomy and Astrophysics Advisory Committee, which counsels the National Science Foundation and Energy Department as well as NASA, concluded that joining Euclid was not in keeping with Academy recommendations.
Caught in the ‘Webb’
By the time the second Academy panel reported in December, news about the Webb telescope’s problems had made everything worse. The Webb, which was the highest Academy priority 10 years ago and has already cost $5 billion, could not be launched any earlier than 2015 and would probably be even later, because of NASA’s inability to correctly estimate how long it would take to do things like test the telescope. How much of the $2.2 billion that NASA was to have available for new astrophysics missions this decade will be left once Webb is taken care of is anybody’s guess. On top of that, NASA faces what Morse calls “an evolved difficult fiscal environment.” Some astronomers said they felt ambushed by NASA and Morse, who briefed the Astro2010 panel during its two years of deliberations.
