March 6, 2015: Dawn arrives in orbit around Ceres. (Note: Scientists don't know the exact nature of Ceres' gravity, and since gravity will affect the spacecraft's travel time, all subsequent dates are estimated.)
April 23, 2015: The spacecraft initially orbits at 8,400 miles above Ceres. Here it starts taking pictures, analyzing the planetoid's surface, and looking for evidence of water vapor.
June 10, 2015: Dawn descends to an altitude of 2,730 miles for a closer look.
Aug. 15, 2015: From an altitude of 910 miles, Dawn extensively maps the surface of Ceres. It snaps photos from different angles, allowing researchers on Earth to gradually build a 3-D view of the landscape.
Dec. 20, 2015: Dawn moves in to its closest orbit, just 230 miles above the surface—nearly 40 times nearer than its first orbit. "It will be like looking at a soccer ball seven inches from your eyes," says Rayman. From here, Dawn takes more detailed observations. It maps Ceres' gravity field, which should reveal how its mass is distributed in the interior (and possibly reveal a subsurface ocean). The spacecraft will also use gamma ray and neutron spectrometers, which measure the signature emissions from different elements in Ceres' crust and interior. This will tell us what Ceres is made of.
June 2016: The mission ends. Though Dawn's fuel and solar panels may keep it alive for a few additional years, the spacecraft could continue to orbit Ceres for hundreds of years.