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NASA has decided to extend the Dawn mission again, but have that extension remain in orbit around Ceres.
A priority of the second Ceres mission extension is collecting data with Dawn’s gamma ray and neutron spectrometer, which measures the number and energy of gamma rays and neutrons. This information is important for understanding the composition of Ceres’ uppermost layer and how much ice it contains.
The spacecraft also will take visible-light images of Ceres’ surface geology with its camera, as well as measurements of Ceres’ mineralogy with its visible and infrared mapping spectrometer.
The extended mission at Ceres additionally allows Dawn to be in orbit while the dwarf planet goes through perihelion, its closest approach to the Sun, which will occur in April 2018. At closer proximity to the Sun, more ice on Ceres’ surface may turn to water vapor, which may in turn contribute to the weak transient atmosphere detected by the European Space Agency’s Herschel Space Observatory before Dawn’s arrival. Building on Dawn’s findings, the team has hypothesized that water vapor may be produced in part from energetic particles from the Sun interacting with ice in Ceres’ shallow surface.Scientists will combine data from ground-based observatories with Dawn’s observations to further study these phenomena as Ceres approaches perihelion.
They aim to get as close as 120 miles of the surface during this extension, half as close as the previous closest approach.