Your report on NASA's next large space telescope, the Wide-Field Infrared Survey Telescope (WFIRST), misleadingly implies that NASA's dark-energy probe faces a cost crisis (Nature 546, 195; 2017). NASA has not yet completed the work of estimating the costs of the mission and is not facing funding difficulties, let alone a crisis.
At the recommendation of the US National Academies of Science, Engineering, and Medicine, NASA is convening an independent technical, management and cost review of WFIRST. The purpose is to ensure that the mission's scope and cost are correctly aligned at this early stage, so that we can proceed with assurance to realize the scientific goals without overspending.
This review was recommended by the National Academies in 2014 and again in 2016, and is not motivated by the mission's current status. We are confident that the review will contribute to the successful development of a breakthrough mission that will reshape our understanding of dark energy, exoplanets and the Milky Way.