Dawn at Ceres: The First Exploration of the First Dwarf Planet

Dawn has 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 its primary mission in June 2016,
Dawn's mission was extended, and new investigations, not previously considered, were conducted
from three new orbits. The mission has provided a uniquely detailed view of the first dwarf planet
discovered. The overall strategy for exploring Ceres was based strongly on the extremely successful
16 months of Vesta operations. Nevertheless, the loss of two of the spacecraft's four reaction wheels
before arrival at Ceres necessitated some important changes in order to conserve hydrazine. These
changes were so effective that Dawn has been able to operate beyond the expected end of life,
acquiring significantly more data than planned. This paper describes Ceres operations in the
primary and extended missions as well as some of the major findings there.