The Dawn spacecraft thundered off the launch pad aboard a Delta II rocket on the first part of its journey to the asteroid belt. Safely perched in the nosecone of the rocket, the probe rode the smoke and fire of the Delta II through the atmosphere on its way into Earth orbit. The nosecone fell away as planned, giving the spacecraft its first taste of the vacuum of space. Telemetry engineers at Cape Canaveral Air Force Station are evaluating the trip so far and are waiting for the second and third stages of the Delta II to fire and send Dawn on its way.
Dawn is expected to send back high-resolution images of these worlds, showing not just craters but also mountains, canyons, and clear evidence of volcanism. Dawn will make a fly-past of Mars on its long journey. The spacecraft will orbit Vesta for about nine months, and Ceres for at least five months. The mission is scheduled to end in July 2015. Visiting two objects and orbiting both is a capability that is only now becoming possible through the development of solar-electric engines. Unlike the chemical rockets of yesteryear which gave probes a short, sharp impulse, the new generation of ion thrusters provide gentle but sustained propulsion. They work by ejecting charged atoms (ions) of xenon. They take time to build up speed - hence Dawn's long mission profile - but they are very efficient and flexible, allowing spacecraft to hop from target to target.