Since March 2015 NASA's Dawn spacecraft investigates the surface of Ceres, the largest dwarf planet in the asteroid belt. Prior to this, the spacecraft orbited dwarf planet Vesta between 2011 and 2012. On 19 October 2017 NASA has authorized a second extension of the Dawn mission. Mission planners estimate the spacecraft can continue operating until the second half of 2018. Dawn will be maneuvered into a new elliptical orbit, which may take the spacecraft to less than 200 kilometers from the surface of Ceres at closest approach.