Next stop: the asteroid belt

We’re one day until launch. NASA’s newest mission, a 3-billion mile, 8-year journey, will explore the asteroid-belt. The mission’s chief engineer, Marc Rayman, sure knows how to build the excitement: "In my view, we’re going to be visiting some of the last unexplored worlds in the inner solar system."

"Dawn" will, appropriately, launch just after sunrise tomorrow morning. That is, if the forecast of rain holds off.

USA Today has the mission details:

Dawn will travel to the two biggest bodies in the asteroid belt between Mars and Jupiter — rocky Vesta and icy Ceres from the planet-forming period of the solar system.

Ceres is so big — as wide as Texas — that it’s been reclassified a dwarf planet. The spacecraft will spend a year orbiting Vesta, about the length of Arizona, from 2011 to 2012, then fly to Ceres and circle there in 2015.

Dawn’s three science instruments — a camera, infrared spectrometer, and gamma ray and neutron detector — will explore Vesta and Ceres from varying altitudes.


Because Vesta and Ceres are so different, researchers want to compare their evolutionary paths.

No one has ever attempted before to send a spacecraft to two celestial bodies and orbit both of them. It’s possible now because of the revolutionary ion engines that will propel Dawn through the cosmos.

Dawn is equipped with three ion-propulsion thrusters. Xenon gas will be bombarded with electrons, and the resulting ions will be accelerated out into space, gently shoving the spacecraft forward at increasingly higher speeds.

"It really does emit this cool blue glow like in the science fiction movies," Rayman said.

NASA tested an ion engine aboard its Deep Space 1 craft, which was launched in 1998. Ion engines have been used on only about five dozen spacecraft, mostly commercial satellites.

Dawn also has two massive solar wings, nearly 65 feet from tip to tip, to generate power as it ventures farther from the sun. Ceres is about three times farther from the sun than Earth.

You can watch the launch live on NASA TV — available on web stream. The "pregame show" begins at 5:15am. The main event will begin sometime between 7:20am and 7:49am:

Dawn’s Sept. 27 launch window is 7:20 to 7:49 a.m. Eastern Daylight Time (4:20 to 4:49 a.m. Pacific Daylight Time). At the moment of liftoff, the Delta II’s first-stage main engine along with six of its nine solid-fuel boosters will ignite. The remaining three solids are ignited in flight following the burnout of the first six. The first-stage main engine will burn for 4.4 minutes. The second stage will deposit Dawn in a 185-kilometer-high (100-nautical-mile) circular parking orbit in just under nine minutes. At about 56 minutes after launch, the rocket’s third and final stage will ignite for approximately 87 seconds. When the third stage burns out, actuators and push-off springs on the launch vehicle will separate the spacecraft from the third stage.