The James Webb Space Telescope (JWST), widely billed as the successor to the Hubble Space Telescope, is facing some serious problems that could lead to scaling back or even canceling the mission. Denver’s Rocky Mountain News and Sky & Telescope magazine both report that JWST is facing potential cost overruns of up to $1 billion, raising the total cost of the mission to over $3 billion. Part of that cost is associated with overruns by prime contractor Northrop Grumman and its subcontractors, while the rest is because the launch of the telescope “could cost more than expected”. (While not explicitly stated, this last statement suggests that NASA is no longer expecting to launch JWST for “free” on an Ariane 5 in exchange for giving ESA a share of the telescope’s observing time, a move that would have required Bush Administration approval under both the old and new space transportation policy.) In response, NASA has asked scientists to consider shrinking the telescope’s diameter from 6.5 to 4 meters, and to remove some of the planned instruments. (Original plans for the then-named Next Generation Space Telescope called for an eight-meter mirror.) Scientists, though, are against such a move, telling S&T that a descoped JWST “wouldn’t be able to compete scientifically with the next generation of giant ground-based telescopes” except in small portions of the infrared. If other efforts to change the telescope or otherwise reduce its costs fail, “outright cancellation is a very real possibility” according to S&T.