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.

Nation:	USA
Type / Application:	Multiple asteroid orbiter
Operator:	NASA
Contractors:	Orbital Sciences Corporation (OSC)
Equipment:	Framing Camera, Mapping Spectrometer, Gamma Ray and Neutron Spectrometer
Configuration:	modified Star-2
Propulsion:	3 NSTAR xenon ion engines
Lifetime:
Mass:	1108 kg
Orbit:	Heliocentric, later orbit around Vesta and Ceres

Satellite	Date	LS		Launcher	Remarks:
Dawn (Discovery 9)	27.09.2007	CC SLC-17B		Delta-7925H

Further Discovery missions: