NASA doesn’t have nearly enough money to do what it wants to do. Well, nothing unusual about that. We’ve talked recently about the constraints that budgetary realities are putting on astronomers’ ambitions — here, here, here. Now it’s chickens-coming-home-to-roost time, apparently. Dennis Overbye has an article in the Times (via Brian Schmidt) about how cost overruns on the James Webb Space Telescope — the giant multipurpose infrared satellite into which basket NASA is putting many of its eggs — are forcing dark energy onto the back burner.
The current NASA vision for dark energy is a mission called WFIRST (Wide-Field Infrared Survey Telescope), which grew out of JDEM (the Joint Dark Energy Mission), which was in turn descended from SNAP (Supernova Acceleration Probe). WFIRST would try to use three different techniques to constrain dark energy parameters — weak lensing, baryon acoustic oscillations, and supernovae. It would also be able to search for exoplanets using microlensing, just as a bonus. But cost overruns on JWST have left NASA with very little money to do ambitious (or even not-very-ambitious) new missions, so WFIRST is now up in the air, despite being judged the highest priority by the National Academy Decadal Survey.
It looks like the U.S. might try to stay in the dark-energy game by funding a 20% share in Euclid, a planned mission by the European Space Agency. Meanwhile, techniques that try to measure parameters of dark energy without leaving the ground are continuing to improve. So maybe it will end up not being a big deal, and we’ll learn what we need to know anyway. Or maybe we’ll miss out on the opportunity for a transformative discovery. The only thing we know for certain is that it’s not easy to make these tough choices when it comes to planning missions over the course of decades.