NASA's Dawn Mission will examine the asteroids Ceres and Vesta. In fact in March 2006 was the Mission canceled but short time later the NASA Management decided to reinstate the Dawn mission, because many scientist all over the world supported the mission.
"We revisited a number of technical and financial challenges and the work being done to address them," said NASA Associate Administrator Rex Geveden, who chaired the review panel. "Our review determined the project team has made substantive progress on many of this mission's technical issues, and, in the end, we have confidence the mission will succeed."
The Dawn spacecraft uses ion propulsion to get the additional velocity needed to reach Vesta once it leaves the Delta rocket. It also uses ion propulsion to spiral to lower altitudes on Vesta, to leave Vesta and cruise to Ceres and to spiral to a low altitude orbit at Ceres.
Dawn's goal is to characterize the conditions and processes of the solar system's earliest epoch by investigating in detail two of the largest protoplanets remaining intact since their formations. By measuring their mass, shape, volume and spin rate with both imagery, laser altimetry and gravity. Dawn records the protoplanets' elemental and mineral composition to determine their thermal history and evolution and provides context for meteorites. Dawn images Ceres and Vesta's surfaces to determine their bombardment and tectonic history, uses gravity and spin state to limit the size of any metallic core, and infrared and gamma ray spectrometry to search for water-bearing minerals.
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
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
Ceres, the largest asteroid and the first to be discovered, is named after the Roman goddess of agriculture. It was discovered by Giuseppe Piazzi of the Palermo Observatory on Jan. 1, 1801.
Vesta, the brightest asteroid, is named for the ancient Roman goddess of the hearth and is the only asteroid ever visible with the naked eye. Found on March 29, 1807, by Heinrich Olbers, it was the fourth minor planet to be discovered. It is the second most massive and the third largest asteroid. It revolves around the Sun in 3.6 terrestrial years and has an average diameter of about 520 km (320 miles). Its surface composition is basaltic.
Framing Camera : German Aerospace Center, DLR, Institute of Space Sensor Technology and Planetary Exploration, Berlin.
Mapping Spectrometer : The Institute for Astrophysics in Space (IAFS), Rome
Gamma Ray and Neutron Spectrometer : Los Alamos National Laboratory, Los Alamos NM