In June 2016, the Dawn spacecraft reached the end of its primary mission over Ceres. Since then, the spacecraft has remained in orbit around the dwarf planet, where it has continued to monitor and study its surface. This week, NASA has announced a second mission extension for the probe, one that will take its closest look yet at the solar system’s largest dwarf planet.
When Dawn arrived in orbit around Ceres in 2015, it provided scientists with an unprecedented look at at the asteroid belt’s largest object, revealing new features (which turn out to be made of salt), an active surface, and even organic compounds. There was still fuel left over once it completed that mission, and while scientists considered sending the spacecraft to another, undisclosed asteroid, they opted to remain in a high orbit to continue studying the object.
For this new mission extension, Dawn’s flight team is looking into ways to bring the probe into a new orbit around Ceres, one that could take it to less than 120 miles above its surface. Previously, Dawn’s lowest orbit brought it to within 240 miles above the dwarf planet. According to NASA, the extension’s primary focus will be to use the spacecraft’s gamma ray and neutron spectrometers to study the upper layer of Ceres’ crust to see how much ice it contains.
The mission extension means that Dawn will be active around Ceres in April 2018 when the dwarf planet is at its closest point to the Sun. Scientists hope that this will show if that closer distance is enough to melt ice on its surface, and if so, if it helps form the thin, transient atmosphere. Scientists will also use Dawn’s visible and infrared mapping spectrometer to study Ceres’ mineral composition, and will continue to take visual-light pictures of its surface.