Dawn at Ceres: The first exploration of the first dwarf planet discovered

Dawn conducted an extensive exploration of dwarf planet Ceres, the largest object between the Sun and Pluto that had not previously been visited by a spacecraft. Following its arrival at Ceres in March 2015, Dawn acquired all the planned data from four circular polar orbits ranging in altitude from 13,600 km to 385 km. After the successful conclusion of the prime mission in June 2016, Dawn's mission was extended, and new investigations, not previously considered, were conducted from four new orbits ranging as low as 35 km. In 2017 the project was approved for a second and final extended mission at Ceres. Starting in April 2018, Dawn used its ion propulsion system to maneuver to two new orbits. These highly elliptical orbits enabled the acquisition of valuable new data, including significant improvements in the spatial resolution. Mission operations concluded in October 2018 upon depletion of hydrazine for attitude control. The mission provided a uniquely detailed view of the first dwarf planet discovered. This paper describes Ceres operations as well as some of the major findings there. •Dawn explored dwarf planet Ceres from 2015 to 2018.•Despite the loss of reaction wheel control, Dawn exceeded its objectives at Ceres.•Using ion propulsion, Dawn operated in 10 distinct orbits to optimize the science.•After two extensions at Ceres, Dawn's mission ended when the hydrazine was depleted.•Dawn revealed Ceres to be a world rich in water, salt, and rock, with diverse geology.