The US National Research Council has published its latest decadal survey, identifying research priorities for astronomy and astrophysics in the years ahead (www.nap.edu/catalog/12951.html). It's an exercise that has taken note of straitened economic circumstances and consulted widely across all of astronomy and astrophysics. Top slot in space has gone to the Wide-Field Infrared Survey Telescope (WFIRST); for large ground-based projects, it's the optical Large Synoptic Survey Telescope (LSST).

It's striking that both WFIRST and LSST are wide-reaching instruments — wide in the area of sky they will survey, wide in the studies they will undertake. Both will target dark energy, the phenomenon invoked to explain the accelerating expansion of the Universe.

These are, of course, only recommendations compiled by representatives of the astronomy community — whether agencies such as NASA decide to run with any of the proposals is another matter. Meanwhile, the European Space Agency (ESA) already has under consideration a proposal for a dark-energy-solving spacecraft, called Euclid; whether it will fly or not is likely to be decided within the next 12 months. NASA and ESA are set to open bilateral talks this month: the quest to understand dark matter would surely be best pursued through international collaboration.