Dawn (Discovery 9)

Dawn [NASA]

Dawn will undertake a journey to the two oldest and most massive asteroids in our solar system, 4 Vesta and 1 Ceres. Dawn will be the first purely scientific mission to be powered by ion propulsion, an advanced technology successfully demonstrated by NASA's Deep Space 1 mission. The use of solar electric ion thrusters will enable Dawn to orbit both asteroids in one mission, a feat that has not been attempted before. Planned for launch in May 2006, Dawn will, after a Mars fly-by, reach 4 Vesta in 2010 and 1 Ceres in 2014. In late 2005, the Dawn mission was delayed to a 2007 launch date instead of the planned June 2006 launch, due to ongoing concerns of the ion engines.

Dawn's science instruments will investigate:

• Internal structure, density and homogeneity of two complementary protoplanets, 1 Ceres and 4 Vesta, one wet and one dry
• Determine shape, size, composition and mass
• Surface morphology, cratering, magnetism
• Determine thermal history and size of core
• Understand role of water in controlling asteroid evolution
• Test the current paradigm of Vesta as the howardite, eucrite, and diogenite (HED) parent body and determine which, if any, meteorites come from Ceres
• Provide a geologic context for HEDs

Science Payload:

• Framing Camera
• Mapping Spectrometer
• Gamma Ray and Neutron Spectrometer
• Laser Altimeter (cancelled)
• Magnetometer (cancelled)

Dawn has been cancelled in February 2006, when the spacecraft was nearly completed. On March, 27th 2006, Dawn was reinstated for a launch in 2007.