NASA's Dawn spacecraft is heading to an encounter with a big asteroid, known as Vesta. Dawn will enter orbit around Vesta (about 530 km across), on 16 July 2011, to make a detailed year-long study of this amazing small world. The mission is expected to start obtaining science data in early August. It is the first orbiting probe to an asteroid.
The asteroids are small rocky objects, orbiting the Sun, mainly between the orbits of Mars and Jupiter, in a zone termed the asteroid belt. They are believed to be primitive material, leftovers from the formation of the Solar System. By studying asteroids, scientists hope to find new insights into the origin and evolution of Earth and the entire Solar System. Interestingly, Vesta is also believed to be the source of some meteorites that fall on Earth.
"The spacecraft is right on target," said Robert Mase, Dawn project manager. "We look forward to exploring this unknown world during Dawn's one-year stay in Vesta's orbit."
Vesta is the second most massive object in the asteroid belt, after the dwarf planet Ceres (approximately 950 km across). It orbits the Sun every 3.6 years, at an average distance of approximately 353 million km. The names Vesta and Ceres come from Roman mythology.
Dawn was launched in September 2007. It has been flying in interplanetary space for nearly four years, and traversed over 2.7 billion km. When Dawn enters Vesta orbit, it will be approximately 16,000 km from the minor planet. At the time of orbit insertion, Vesta will be approximately 188 million km from Earth. In July 2012, Dawn will leave Vesta, to voyage to Ceres. It is expected that Dawn will reach Ceres in February 2015. The primary mission will end in July 2015.
Images acquired by a camera onboard Dawn, taken for navigation purposes, reveal the spacecraft’s slow approach to Vesta and the rotation of Vesta about its axis. These images are not sharp yet, however, they are better in quality than the images of Vesta from NASA's Hubble Space Telescope, a sophisticated space-based observatory, exploring the universe from Earth orbit.
References
NASA
www.nasa.gov/
NASA’s Dawn Website
http://www.nasa.gov/mission_pages/dawn/mission/index.html
Wikipedia
Further Reading
Asteroids
http://nineplanets.org/asteroids.html