NASA’s Dawn spacecraft is on its way to study a pair of asteroids after lifting off Thursday, September 27, 2007 from the Cape Canaveral Air Force Station at 7:34 am EDT (4:34 am PDT). Mission controllers at NASA’s Jet Propulsion Laboratory, Pasadena, Calif., received telemetry on schedule at 9:44 am EDT (6:44 am PDT) indicating Dawn had achieved proper orientation in space and its massive solar array was generating power from the sun. During the next 80 days, spacecraft controllers will test and calibrate the myriad of spacecraft systems and subsystems, ensuring Dawn is ready for the long journey ahead. Dawn’s 4.8-billion-kilometer (3-billion-mile) odyssey includes exploration of asteroid Vesta in 2011 and the dwarf planet Ceres in 2015. These two icons of the asteroid belt have been witness to much of our solar system’s history. By using Dawn’s instruments to study both asteroids, scientists more accurately can compare and contrast the two. Dawn’s science instrument suite will measure elemental and mineral composition, shape, surface topography, and tectonic history, and will also seek water-bearing minerals. In addition, the Dawn spacecraft and how it orbits Vesta and Ceres will be used to measure the celestial bodies’ masses and gravity fields. The spacecraft’s engines use a unique, hyper-efficient system called ion propulsion, which uses electricity to ionize xenon to generate thrust. The 30-centimeter-wide (12-inch) ion thrusters provide less power than conventional …
