NASA’s Dawn was the first mission to orbit an asteroid, beginning operations around Vesta in 2011.
Dawn entered orbit around the large asteroid Vesta on July 16, 2011, and studied it for more than a year. It then departed Vesta and reached the dwarf planet Ceres in March 2015, becoming the first spacecraft to orbit two extraterrestrial bodies.
The spacecraft used solar-electric ion propulsion, which provided gentle but highly efficient thrust over long periods. This technology enabled Dawn to travel between two bodies in the asteroid belt rather than making a single flyby.
Dawn’s later Ceres observations revealed bright deposits in Occator Crater, identified as reflective salts. Although Dawn is famous for visiting both Vesta and Ceres, the specific first asteroid-orbiting milestone occurred at Vesta.