NASA’s Dawn spacecraft is a “Go” for the asteroid belt

NASA’s Dawn spacecraft is a “Go” for the asteroid belt

Press release from: Kennedy Space Center
Posted: Tuesday September 25th 2007

CAPE CANAVERAL, Fla. — Launch and flight crews are preparing for the scheduled Sept. 27 liftoff from Pad 17-B at Cape Canaveral Air Force Station, Fla., of NASA’s Dawn mission. The Dawn spacecraft will venture into the heart of the asteroid belt, where it will document in exceptional detail the gigantic rocky asteroid Vesta and then the even larger icy dwarf planet Ceres.

“If you live in the Bahamas, that’s one time you can tell your neighbor, with a straight face, that Dawn will rise in the west,” said Keyur Patel, Dawn project manager, from the Jet Propulsion Laboratory in NASA in Pasadena, California. “Weather permitting, we leave for the launch Thursday morning shortly after dawn.”

Dawn’s September 27 launch window is 7:20 a.m. to 7:49 a.m. Eastern Daylight Time (4:20 a.m. to 4:49 a.m. Pacific Daylight Time). Upon liftoff, the Delta II’s first-stage main engine and six of its nine solid-fuel boosters will ignite. The three remaining solids ignite in flight following the exhaustion of the first six. The first stage main engine will burn for 4.4 minutes. The second stage will drop Dawn into a 185 kilometer high (100 nautical mile) circular parking orbit in just under nine minutes. About 56 minutes after launch, the rocket’s third and final stage will ignite for about 87 seconds. When the third stage burns up, the launcher’s actuators and thrust springs separate the spacecraft from the third stage.

“After separation, the spacecraft will go through an automatic activation sequence, including stabilizing the spacecraft, activating the flight systems, and deploying Dawn’s two massive solar arrays,” Patel said. “Then, and only then, will the spacecraft energize its transmitter and contact Earth. We expect signal acquisition to occur between one and a half and three and a half hours after launch.”

The Dawn mission will explore Vesta, and later Ceres, as these two giants of the asteroid belt have witnessed much of our solar system’s history.

“Visiting both Vesta and Ceres allows for a study of extraterrestrial contrasts,” said Dawn lead researcher Christopher Russell of the University of California, Los Angeles. “One is rocky and is representative of the building blocks that constructed the planets of the inner solar system. The other may very well be icy and represents the outer planets. Yet these two very diverse bodies essentially reside in the same vicinity. This is one of the mysteries Dawn hopes to solve.”

Using the same spacecraft to recognize two different celestial targets makes more than fiscal sense. It makes scientific sense. By using the same set of instruments at two separate destinations, scientists can more accurately formulate comparisons and contrasts. Dawn’s suite of scientific instruments will measure mass, shape, surface topography and tectonic history, elemental and mineral composition, as well as search for aquifer minerals. Additionally, the Dawn spacecraft itself and the way it orbits both Vesta and Ceres will be used to measure the gravity fields of celestial bodies.

“Understanding the conditions that lead to planet formation is a goal of NASA’s exploration mission,” said David Lindstrom, Dawn program scientist at NASA Headquarters in Washington. “The science returned by Vesta and Ceres could reveal many mysteries of the formation of rocky planets, including Earth.”

Before all of this celestial mystery unlocking can happen, Dawn must reach the asteroid belt and her first target – Vesta. It’s a four-year process that begins with launch and continues with the firing of three of the most efficient engines in NASA’s space engine inventory – the ion propulsion engines. Using a complex mix of solar-derived electrical energy and xenon gas, these frugal powerhouses must run for months at a time to propel and steer Dawn. Over their eight-year lifespan, or nearly 4 billion miles, these three ion-powered engines will operate cumulatively for about 50,000 hours (over five years) – a record for spacecraft.

The Dawn mission to the asteroid Vesta and the dwarf planet Ceres is managed by JPL, for NASA’s Science Mission Directorate, Washington, DC JPL is a division of the California Institute of Technology in Pasadena. The University of California, Los Angeles is responsible for all Dawn mission science. Other scientific partners include: Los Alamos National Laboratory, New Mexico; Max Planck Institute for Solar System Research, Katlenburg, Germany; and Italian National Institute of Astrophysics, Rome. Orbital Sciences Corporation of Dulles, Virginia designed and built the Dawn spacecraft.

Additional information about Dawn is available online at http://www.nasa.gov/dawn Where http://dawn.jpl.nasa.gov . For more information about NASA and agency programs on the Internet, visit http://www.nasa.gov .

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