Dawn on approach to Ceres using ion engine

The dwarf planet Ceres, viewed from NASA’s Dawn spacecraft on January 13, 2015 from about 238,000 miles (383,000 km). The image cycle represents 1 hour of time. Original NASA image here.

The Dawn mission to the asteroid belt (between Mars and Jupiter) is approaching its second target. The spacecraft is closing in on Ceres after having visited Vesta a few years ago. It is planned to enter Ceres’ orbit in early March and will stay there for 16 months. This mission is remarkable not just for its scientific value, but also because the spacecraft’s propulsion system is somewhat nonstandard. Instead of typical chemical rockets and thrusters, Dawn uses an ion drive that, while low thrust, is extremely fuel-efficient. That choice of main drive allowed mission planners to knock off two items on the hit list–Vesta and Ceres–for the price of one.

NOTE ADDED 2/5/15: And closer…